Golden Gate— 

phy, Geology, Biology, and 

ntal Issues in the Gulf of the Farallones 
Edward Ueber, 

W. Hendley II 

Golden Gate— 

phy, Geology, Biology, and 

tal Issues in the Gulf of the Farallones 
in this publica

does not imply 

2001 

lable at 

8/ 

nd at 

d its products: 

–8747) 

Park, California 

e 18, 2000 

d Susan Mayfield 

Stauffer, 

ach 

 

Cooperating Organizations Bodega Marine Laboratory (University of California at Davis) British Geological Survey California Department of Health Services Environmental Protection Agency Kernfysisch Versneller Instituut, Groningen, The Netherlands National Oceanic and Atmospheric Administration 

Gulf Of The Farallones National 

Marine Sanctuary 

Cordell Bank National Marine Sanctuary National Marine Fisheries Service 

National Park Service
Point Reyes Bird Observatory
U.S. Army Corps of Engineers
U.S. Geological Survey
U.S. Navy


Contributors 

Bodega Marine Laboratory (University of California at Davis) 

Stephen R. Wing 

British Geological Survey 

David G. Jones Philip D. Roberts 

California Department of Health Services 

Gregg W. Langlois Patricia Smith 

Environmental Protection Agency 

Allan Ota 

Kernfysisch Versneller Instituut, Groningen, The Netherlands 

Johannes Limburg 

National Oceanic and Atmospheric Administration 

Gulf of the Farallones National 

Marine Sanctuary Jan Roletto Edward Ueber 

Cordell Bank National Marine Sanctuary 

Dan Howard 

National Marine Fisheries Service 

Peter Adams Tom Laidig 

National Park Service 

Scot Anderson 

Point Reyes Bird Observatory 

Scot Anderson Peter Pyle 

U.S. Geological Survey 

John L. Chin Walter E. Dean James V. Gardner Russell W. Graymer James W. Hendley II Herman A. Karl Kaye Kinoshita Marlene A. Noble Stephanie L. Ross Holly F. Ryan William C. Schwab Peter H. Stauffer Florence L. Wong 
Contents


1 2 4 6 8 

12 16 20 24 26 28 

30 32 36 40 42 44 48 52 56 60 62 66 68 72 72 73 75 77 

ck pocket 

Foreword Charles G. Groat
Beyond the Golden Gate—Introduction Herman A. Karl and Edward Ueber
Techniques and Technology of Exploration in the Gulf of the Farallones Kaye Kinoshita and John L. Chin


Oceanography and Geology of the Gulf of the Farallones 

Regional Setting John L. Chin and Russell W. Graymer Earthquakes, Faults, and Tectonics Holly F. Ryan, Stephanie L. Ross, and Russell W. Graymer Landscape of the Sea Floor Herman A. Karl and William C. Schwab Current Patterns Over the Continental Shelf and Slope Marlene A. Noble Sediment of the Sea Floor Herman A. Karl Chemical Composition of Surface Sediments on the Sea Floor Walter E. Dean and James V. Gardner Heavy-Mineral Provinces on the Continental Shelf Florence L. Wong 

Biology and Ecological Niches in the Gulf of the Farallones 

Phytoplankton Gregg W. Langlois and Patricia Smith Krill Dan Howard Free-Floating Larvae of Crabs, Sea Urchins, and Rockfishes Stephen R. Wing Salmon Peter Adams Seabirds Peter Pyle Marine Mammals Jan Roletto White Sharks Scot Anderson Continental Slope Communities Tom Laidig 

Issues of Environmental Management in the Gulf of the Farallones 

Disposal of Dredged Material and Other Waste on the Continental Shelf and Slope John L. Chin and Allan Ota Search for Containers of Radioactive Waste on the Sea Floor Herman A. Karl Measuring Radioactivity from Waste Drums on the Sea Floor David G. Jones, Philip D. Roberts, and Johannes Limburg 

Further Reading 

Oceanography and Geology Biology Environmental Issues 

Glossary CD-ROM containing full-length technical version of Circular 1198 

eword


ientists and decisionmakers have become increasingly aware of the need to understand the 

xity of natural systems when considering actions that affect individual aspects of resources and the 

ment. The interconnectedness of the physical and biological elements of a natural system is often 

iated in the abstract, but sometimes not as much as it should be in scientific studies. Too frequently, 

e interaction of all elements of a system influence the organism, habitat, or process being focused 

ven only lip service or general observations. Although not intended to be an integrated study, this 

on oceanographic, geological, biological, and environmental aspects of the Gulf of the Farallones 

xcellent example of a study describing the many facets of a complex marine system. 

ne systems, the geologic foundation and sediment dynamics of the sea floor define the basic 

ment for communities of bottom-dwelling organisms, which are influenced by circulation patterns 

o affect organisms living in the water column. Decreased light penetration caused by turbidity 

the plankton, the base of the marine food web, and thus affects fish and other marine populations. 

metimes consider the most dynamic and influential elements of marine systems to be the currents, 

and mobile species that are monitored regularly because they change frequently on a human time 

However, this report demonstrates how geologic processes, including crustal processes manifested 

hquakes, can also be influential on the same time scale. The inclusion of a chapter on tectonics 

this point home. 

port also demonstrates the impact that a past tendency towards an “out of sight, out of mind” 

ch to the use of the ocean floor for waste disposal has had on future use of marine resources and 

w technology can improve the situation. Concerns over possible leakage from drums of radioactive 

dumped until about 1970 on the ocean floor in the Gulf of the Farallones affected the marketability 

caught in the area. Technology has only recently enabled scientists to locate the drums and begin 

ng the actual risk. Similarly, new technology has allowed proposed sites for disposal of dredged 

al to be evaluated with a more thorough understanding of bottom conditions and processes. 

 that help provide an integrated knowledge of complex natural systems, like these on the Gulf of the 

nes, give decisionmakers and the public an enhanced ability to avoid the mistakes of the past and 

e sustainable use of environments and resources essential to human society. 

s G. Groat 


or, U.S. Geological Survey


1

olden Gate—Introduction


ean fascinate 

a source of 

lation, and 

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d since pre

n discovered 

a, the life in 

th the sea 

in mystery. 

occupy 71 

d are crucial 

n learning 

st in learn

sea. 

 open space 

ans are a 

 and play 

on. This 

n those areas 

ban com

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ncerns must 

economic, 

ent large 

creasing 

stems of the 

ny areas of 

ates have 

nctuaries and 

onal Marine 

lf of the Far

etch more 

than 185 miles from Bodega Bay north of San Francisco to Cambria south of Monterey. They protect an area larger than the States of Connecticut and Rhode Island combined, about 7,000 square miles of the California coastal ocean. 

The U.S. Geological Survey (USGS) 

began a major geologic and oceanographic study of the Gulf of the Farallones in 1989. This investigation, the first of several now being conducted adjacent to major population centers by the USGS, was undertaken to establish a scientific data base for an area of 1,000 square nautical miles on the Continental Shelf adjacent to the San Francisco Bay region. The results of this study can be used to evaluate and monitor human impact on the marine environment. 

In 1990, the project expanded in scope 

when the USGS sponsored a multidisciplinary investigation with four other Federal agencies—Environmental Protection Agency, Army Corps of Engineers, U.S. 

Navy, and Gulf of the Farallones National Marine Sanctuary (part of the National Oceanic and Atmospheric Administration)—to survey and sample the Continental Slope west of the Farallon Islands. This study was primarily designed to provide information on the location and distribution of approximately 47,800 containers of lowlevel radioactive waste and obtain data on 

areas being considered as potential sites for the disposal of sediments dredged from San Francisco Bay. 

Many other organizations eventually participated in this work, including Point Reyes 

Bird Observatory, California Department of Health Services, and the British Geological Survey. The information from these studies is being used by the Gulf of the Farallones National Marine Sanctuary to better manage and protect the unique ecological resources of the gulf. This information was also used in 1994 by the Environmental Protection Agency in designating the first deep-ocean 

disposal site for dredged material on the Pacific coast of the United States, west of San Francisco on the Continental Slope outside the boundaries of the sanctuary. 

This USGS Circular endeavors to pull 

back the shroud of mystery that covers the ocean waters seaward of the Golden Gate, 

revealing to the reader some of the diverse 

habitats and ecosystems in the Gulf of the Farallones and discussing issues of contamination and waste disposal. The sections of this book cover the topics of Oceanography and Geology, Biology and Ecological Niches, and Issues of Environmental Management in the Gulf of the Farallones. 

The chapters in the paper version of the 

book are short, less technical summaries. The full chapters are contained on the 

CD–ROM in the pocket at the back of the book. Links to the complete Circular 

and related topics can be found at http:// 

walrus.wr.usgs.gov. 

Acknowledgments.—The view of the Gulf of 

the Farallones presented here resulted from the efforts of scores of people over a 12-year period, from the first sampling and surveying cruise in 1989 to final publication of this book in 2001. It is not possible to single out each person who contributed in one way or another to this endeavor. The work of each is greatly appreciated, but some deserve 

special mention. William Schwab, David Twichell, 

David Drake, and David Rubin served as co-chief 

scientists with John Chin and Herman Karl on the 1989 and 1990 cruises and contributed significantly to their design and implementation. William Danforth and Thomas O’Brien led the teams that processed sidescan-sonar data in near-real time while 

at sea. Arthur Wright of Williamson and Associates provided helpful insights during the search for barrels of radioactive waste using the SeaMARC1A 

sidescan sonar. Pat S. Chavez, Jr., and his group 

did preliminary computer enhancements of sidescan images that helped identify nongeologic features on the sea floor, such as radioactive waste barrels. 

John Penvenne of Triton Technologies developed 

the principal methodology to detect barrels and classify objects in the SeaMARC1A imagery. Kaye Kinoshita and Norman Maher supported the early stages of assembling this book. William van Peeters 

coordinated the use of the U.S. Navy’s DSV Sea Cliff and Advanced Tethered Vehicle. The USGS 

Marine Facility in Redwood City, California, provided operational support on shore and at sea. 

The officers and crews of the USGS ship R/V Farnella, NOAA ship R/V McArthur, the Navy’s 

ship Pacific Escort, and the support vessel Laney Chouest greatly aided the work in the gulf. 

ntroduction 
AP OF THE SAN FRANCISCO BAY REGION AND THE GULF OF THE FARALLONES


CORDELL BANK 

NATIONAL MARINE 

SANCTUARY 

MONTEREY BAY 

NATIONAL MARINE 

SANCTUARY 

Bodega Head 

Bodega Bay 

SAN 

FRANCISCO 

OAKLAND 

SAN JOSE 

Richmond 

Santa 

Cruz 

Monterey 

Año 

Nuevo 

Point 

Reyes 

Alameda 

Livermore 

Vallejo 

Bolinas 

Lagoon 

San 

Pablo 

Bay 

Tomales Bay 

Half Moon 

Bay 

GULF OF THE FARALLONES 

NATIONAL MARINE SANCTUARY 

Farallon Islands 

Sacramento River 

S A N 

F R A N C I S C O 

B A

Y 

Suisun Bay 

38°00'N 

37°30' 37°00' 

122°30'W 122°00' 

Golden Gate Peninsula Marin

M O N T E R E Y 

B A

Y 

PACIFIC 

OCEAN 

Farallon Islands 

0 20 KILOMETERS 

0 20 MILES 

Noonday Rock 

North Farallon 

Middle 

Farallon 

Southeast Farallon 

Seal Rock 

Maintop 

Island 

123°00'W 

37°45'N 

Farallon Islands 

0 5 KILOMETERS 

0 5 MILES

Beyond the Golden Gate—Introduction 3

 percent of 

ue to be 

om the 

nto the 

ng into 

hazardous. 

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a types 

together in a spatial frame of reference. Four types of navigation sensors were used to determine the locations of objects and features on the sea floor—Global Positioning System (GPS) satellites, Loran-C, and two ranging navigation systems (Del Norte and Benthos). The output from the GPS, Loran-C, and Del Norte systems was fed directly into a navigation program running on a microcomputer. This program provided important real-time location information, which was relayed to computers in 

onboard science laboratories and the ship’s bridge. The Benthos system was a standalone system, which had its own program and display and ran separately from the integrated navigation system. 

Two types of equipment using sound 

waves—sidescan sonar and seismic-reflection systems—were used to map the sea 

floor in the gulf. Images from three different sidescan systems were cut and pasted together to create “mosaics,” which provide excellent map views of the area of sea floor studied in the gulf. Both 3.5-kilohertz (kHz) and 4.5-kHz high-resolution seismic-reflection systems were used to profile and look at the shallow subbottom (uppermost 160 feet) of the sea floor. A 10-kHz system was also used to provide accurate bathymetric information. 

A towed seabed gamma-ray spectrometer belonging to and operated by the 

British Geological Survey, called the EEL because of its eel-like appearance, was used to measure the radioactivity of the sea floor. The gamma detector can measure both natural and artificial radioactivity in 

surficial sea-floor material to an effective 

maximum subbottom depth of about a foot. As the probe is towed, data are sent up the towing cable to a shipboard computer and recorded continuously. 

Physical samples of the sea bottom 

were taken with two devices. A gravity 

corer, driven into the bottom by a heavy 

weight, was used to obtain round cores about 4 inches in diameter and as much as 10 feet long. This type of coring device was used where the sediment was expected to be soft and muddy. The other sampling device used was a Van Veen grab sampler, 

which works very much like a clam shell. 

When the two sides of the shell touch the sea floor they close and scoop up a sample. This device was used where the sea floor 

was expected to be sandy, because sand would not easily be penetrated by or retained in a gravity corer. 

Instrument packages were attached to 

lines moored to the sea floor to measure the velocity and direction of ocean currents 

in the Gulf of the Farallones. These instrument packages also measured water clarity, 

conductivity, salinity, and temperature. 

A camera sled designed and built by 

the U.S. Geological Survey was towed 

from a research vessel along a preplanned trackline to take pictures of the sea floor in 

the gulf. Video was recorded continuously 

and still photographs were taken every 

10 to 15 seconds. The images of the sea floor obtained with the camera sled were used to visually verify information collected from both sidescan-sonar mapping and physical sampling. 

Visual observations were also made 

with Sea Cliff, a manned deep-submergence vehicle (DSV) operated by the U.S. 

Navy. Sea Cliff also had the capability to take physical samples with the use of mechanical arms. The Navy’s unmanned 

Advanced Tethered Vehicle (ATV) was 

also used to obtain additional video and photographs of the sea floor. The ATV can 

be remotely “driven” to a specific site, and 

it proved to be the most precise way used 

so far in the Gulf of the Farallones to view 

objects on the sea floor. 

of Exploration in the Gulf of the Farallones

and Technology of Exploration in the Gulf of the Farallones 
Techniques and Technology of Exploration in the Gulf of the Farallones 5 

es—sidescan sonar and seismic-reflection systems—were 

he Farallones. Each system is housed in a hydrodynamic 

ean surface from a ship. The SeaMARC1A sidescan-sonar 

ctive shell. The inset shows the towfish that was used for 

s. 

Samples of the sea bottom were taken with two devices. A gravity corer (above) was used where the sediment was expected to be soft and muddy. A clam-like Van Veen grab sampler (left, in closed 

position), used where the sea floor was expected to be sandy, collected samples such as the sand and 

brittle stars shown (top). 

This U.S. Geological Survey camera sled, towed from a research vessel along preplanned tracklines, was used to take pictures of the sea floor in the Gulf of the Farallones. 

Sea Cliff (above), a manned deep-submergence vehicle operated by the U.S. Navy, was used to directly observe the sea bottom and to take physical samples with its mechanical arms. The Navy’s unmanned Advanced 

Tethered Vehicle (above right) was also used to take video footage and still photographs of the sea floor. 
Bay region of California is famous for its stunning landscapes and 

djacent to this region, in the watery world of the Pacific Ocean 

Gate, lies the Gulf of the Farallones, a physical environment equally 

ating, but less obvious, less visible, and therefore more mysterious. 

are revealing that the sea floor of the gulf, like the region onshore, 

ogic forces that include movements of the San Andreas Fault system, 

a level, and the action of rivers. The ceaseless work of oceanic 

 sculpted the sea bottom in the gulf into landscapes that today range 

giant sand ripples to deep canyons and rugged mountains, some of 

mits poke above the water to form the Farallon Islands. 

y of the Gulf of the Farallones 

ting 

er 

 in the off

o Bay region 

The bay 

million 

rded as 

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ws hundreds 

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erience its 

 The histori

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on extends 

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oaquin Delta 

area out to 

feet, which 

ental Slope. 

y residents 

 watch the 

 well as to 

f of the Far

s. Although 

t be visually 

ed much 

uments 

 sources and 

listening devices) and underwater cameras and video equipment. 

The landscape features of the San 

Francisco Bay region are the cumulative result of millions of years of Earth history, involving the building and subsequent wearing down of mountains, volcanic eruptions and resulting outpourings of lava, large and small earthquakes, and the never-ending processes of wind and water erosion and deposition. Many of these processes are occurring today, although some of them occur at rates so slow that little change may be perceived over the course of a human lifetime. The sedimentary deposits and rocks of the region range in age from hundreds of millions of years to those still forming today. The entire spectrum of rocks present in the region records only a fraction of the Earth’s history. The rock types range from the salt-and-pepper granitic rocks at Point Reyes and on the Farallon Islands, through various types of volcanic rocks (such as the pillow basalts in the Marin Headlands), to sedimentary rocks, such as the red to brown bricklike chert that forms the cliffs of the Marin Headlands and many of the hills of San Francisco, and the young sand-dune deposits that occur along the Pacific Coast. 

The San Francisco Bay region straddles the boundary zone between two of the 

Earth’s major tectonic plates. The Pacific 

Plate is slowly moving northward relative 

to the North American Plate, and this motion takes place along the San Andreas Fault and a network of associated subparallel faults, collectively called the San 

Andreas Fault Zone (see chapter on Earthquakes, Faults, and Tectonics). Rocks east of the San Andreas Fault Zone were mainly formed in approximately their present positions. However, many of the 

rocks found within the zone, like the Franciscan chert at the Marin Headlands, are ocean-floor rocks that have been scraped off onto the edge of North America over the past 150 million years. 

The oldest of the rocks found west of 

the San Andreas Fault were formed hundreds of miles to the south, some near 

the present site of Los Angeles, and subsequently transported northward by movement along the San Andreas and its associated faults. Rocks west of the fault 

are, in fact, still being transported northward at about 2 inches per year and after millions of years may reach the area where Alaska is today. 

Mountain ranges in the San Francisco 

Bay region trend mostly northwest and are 

separated by broad basins and narrow valleys. Many of the ridgecrests in the 

Coast Range, the major mountain range in the region, rise above 1,000 feet, and a 

few above 4,000 feet. The highest peaks include Mount Hamilton at 4,373 feet, Mount Diablo at 3,849 feet, and Mount Tamalpais at 2,606 feet. 

As recently as about 10,000 years ago, 

at the end of the last ice age, great sheets of ice (glaciers) covered much of Earth’s 

northern hemisphere. Because so much water was stored in these glaciers, sea level was about 300 feet lower than at present, and the coastline of the San Francisco Bay region was situated as much as 35 miles seaward of its present position, near coastal hills whose tops are now the Farallon Islands. The melting of the ice sheets caused worldwide sea level to rise, 

forming the Gulf of the Farallones and San Francisco Bay. 

If the vast volume of ocean water that 

now covers the floor of the gulf could be 

removed, people would see a varied landscape. That landscape is as rich in diversity and rugged splendor as that on the 

nearby shore (see chapter on Landscape of the Sea Floor). 

of the Gulf of the Farallones 
A 

B 

The Gulf of the Farallones lies in the offshore part of the San Francisco Bay region (see map at left) just beyond the Golden Gate (views above). A, View eastward from the Marin Headlands toward the Golden Gate Bridge and downtown San Francisco; Alcatraz Island can be seen at the upper left, Treasure and Yerba Buena Islands and the San Francisco Bay Bridge are seen in the middle distance, and the hills of the heavily populated east bay, which includes the city of Oakland, can be seen beyond the Bay Bridge. B, View westward through the Golden Gate looking out into the Gulf of the Farallones. C, Closeup westward view of the Marin Headlands taken from a similar vantage point as photograph A; the headlands are mostly composed of Franciscan chert and pillow basalts (see next page). (U.S. Geological Survey photographs by Phil Stoffer.) 

Regional Setting 9 

C 
Some rocks of the San Francisco Bay region 

dating from the Mesozoic Era (250 to 65 million years ago): Franciscan cherts (top left) and pillow basalts (bottom left) of the Marin Headlands, which were originally formed on the ocean floor 150 to 100 million years ago. (U.S. Geological Survey photographs by Bruce Rogers.) 

Some sedimentary rocks of the San Francisco Bay region dating from the Tertiary Period (65 to 1.6 million years ago). Above, deposits of an approximately 50-million-year-old submarine landslide exposed near Año Nuevo on the coast south of San Francisco; left, a beach cobble of the Purisima Formation on the coast south of San Francisco containing abundant fossils, mostly clams, that lived in shallow marine waters a few million years ago and are similar to those living in the region’s coastal waters today. (U.S. Geological Survey photographs by Phil Stoffer.) 

of the Gulf of the Farallones 
Geologic map of 

San Francisco Bay region, showing the San Andreas Fault, related faults, and regional rock types. 

use the winds at the time of the 


veral inches thick was deposited as 


Map shows known distribution of the 


rom it magnified about 70 times.


Regional Setting 11 
y of the Gulf of the Farallones 

, Faults, and Tectonics 

nd Russell W. Graymer 

rancisco 

ne of the 

 in history. 

ke began 

reas Fault 

ulf of the 

offshore 

 ruptured 

 from 

endocino. 

aking 

 with 

uing fire, 

sco, a 

t the time. 

oll from 

to be about 

d that the 

o four 

ore than 50 

the city 

earthquake. 

an area 

le covers 

es around 

mall earth

on every 

eater than 

ly felt. The 

rieta earth

r of the 

potential for large, destructive earthquakes in the region. The Loma Prieta 

earthquake killed 63 people, injured more than 3,700 others, and caused property damage in excess of $6 billion. It should be kept in mind, however, that devastation occurred only in 

limited areas because the epicenter of this earthquake was on a somewhat 

remote segment of the San Andreas Fault, 70 miles south of San Francisco in the Santa Cruz Mountains. An earthquake of similar magnitude located closer to the center of a densely populated urban area is capable of causing much greater damage and loss of life. This was shown by the 1995 

Kobe, Japan, earthquake (magnitude 6.9), which caused more than 6,000 deaths, injured 35,000 people, resulted in $100 billion in property damage, and destroyed the homes of more than 300,000 people. 

The rigid outer shell of the Earth 

is made up of large “tectonic plates” that move horizontally relative to one another. The Gulf of the Farallones 

includes part of the boundary between two of the Earth’s largest tectonic 

plates. Tectonic motion along this boundary is what makes the San Francisco Bay region so susceptible to earthquakes and is a significant factor in creating the geology and geomor­ phology of the region. The Pacific and North American Plates are sliding relentlessly past each other at an aver- age rate of about 2 inches per year. Most of this motion occurs in cat­ astrophic bursts of movement—earth­ quakes—along the San Andreas Fault system. Near San Francisco, the San Andreas Fault system is a complex zone of faults about 50 miles wide. It stretches from offshore to as far east as the cities of Vallejo and Livermore. In addition to the San Andreas Fault, the numerous faults that are part of the San Andreas Fault system include the San Gre­ gorio, Hayward, Rogers Creek, and Calaveras Faults. Much of the geomorphology (sur­ face features) of the San Francisco Bay region is a consequence of the location and motion of past and pres­ ently active faults within the San Andreas Fault system, and of the jux­ taposition of blocks of different rock types by movements along these faults. For example, the Farallon Islands off- shore and Montara Mountain located onshore north of Half Moon Bay are parts of large fault blocks that contain granitic rocks believed to be originally derived from the southern Sierra Nevada. At least 17 such fault- bounded structural blocks (terranes) of different sizes and rock types have been identified in the bay region. To help reduce injuries and prop­ erty damage from future earthquakes in the San Francisco Bay region, it is necessary to have a good understand­ ing of the geology of this region. This must encompass both the onshore and offshore geology, including that of the Gulf of the Farallones. 

of the Gulf of the Farallones 
The photograph above, taken from a 

“captive airship” 5 weeks after the great earthquake of April 18, 1906, shows the devastation wrought on the city of San Francisco by the quake and subsequent fire. In the city and surrounding region, the official death toll was about 700, but it is now believed that the actual loss of life was three to four times greater. At the time, property losses were estimated to be more than $400 million. If a similar earthquake occurred in northern California today, after many decades of rapid urban growth, many thousands of people might be killed, and economic losses could be in the hundreds of billions of dollars.The photograph at left shows a fence near Bolinas, about 20 miles southeast of Point Reyes, that was offset by ground movement along the San Andreas Fault in the 1906 quake. 

The San Francisco Bay region lies on the boundary zone between two of the major tectonic plates that make up the Earth’s outer shell. The continuous motion between the Pacific and North American Plates, distributed across this zone, is monitored by geophysicists using the satellite-based Global Positioning System (GPS). Arrows on this map depict recent (mid to late 1990’s) rates of movement, relative to the interior of the North American Plate, of 

reference markers anchored in rock or deep in solid ground. This relentless motion of the plates strains the crustal rocks of the bay region, storing energy that eventually will be released in earthquakes. During the time represented in this diagram, most of the faults in the bay region have been “locked,” not producing earthquakes. 

Earthquakes, Faults, and Tectonics 13 
Terrane map of the San Francisco Bay region. 

Beneath the landscape of the bay region lie fragments of at least 17 different bedrock types that have been transported and juxtaposed by movement along faults. The major basement rock types can be ascribed to either the Franciscan terranes or the Salinian terranes. Rocks of the Salinian terranes, whereas those east of the San Andreas Fault are generally part of the rock types that formed in very different geologic environments and some of which were transpresent positions. west of the San Andreas Fault are generally part Franciscan terranes. These major terranes, separated by the San Andreas Fault, are composed of ported long distances by tectonic motion to their 

of the Gulf of the Farallones 
he U.S. Geological Survey 

erators released this earthquake 

ty map for the San Francisco Bay 

he threat of earthquakes extends 

e entire region, and a major 

ikely before 2030. As continuing 

reveals new information about 

kes in the bay region, these 

ties are revised. 

Earthquakes, Faults, and Tectonics 15 
y of the Gulf of the Farallones 

f the Sea Floor


wab 

ace of the 

mall that 

 thousands 

n an inch 

y see these 

and, and 

ored and 

and drive 

ntrast, 

ut ever 

of large 

idden by 

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mpossible 

he sea 

and so the 

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ap the fea

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, and we 

ger than any 

nd wider 

beneath our 

e land sur

aircraft and 

es. Optical 

reflected 

ographs) 

nd valleys. 

However, light does not penetrate far in water, and so photographs cannot be produced that show entire mountains and valleys beneath the sea. Just as underwater cameras can take photographs of only very small areas and objects not far distant, divers and submersibles can observe only very small areas of the 

ocean bottom. Such methods of observation are analogous to walking around at night with a flashlight and trying to see a mountain or a forest. It is possible in this way to see rocks, pebbles, leaves, and trees along your path, but not the entire mountain and forest. To observe and make images of the mountains and valleys under the sea, scientists have developed instruments that use sound (acoustic energy) as a way to “insonify” (flood with sound waves) rather than illuminate (flood with light) those features. Computers are used to process the acoustic data so that the resulting sound images (sonographs) resemble aerial photographs (light images). 

Data collected from the Continental 

Shelf in the Gulf of the Farallones by the U.S. Geological Survey (USGS) reveal various features on the seabed, including outcropping rock and several types of ripples, dunes, lineations, and depressions (these features are collectively called bedforms). A regional map com­ piled from these data established that at least four major discrete fields of bed- forms occur on the Continental Shelf between Point Reyes and Half Moon Bay. These fields are separated by monotonous stretches of flat, featureless sea floor. Of particular interest is a series of depressions floored by ripples with wavelengths of about 3 feet. These depressions, which are common east of the Farallon Islands between Point Reyes and the Golden Gate, form the largest of the four fields of bedforms. The shelf in the study area is morphologically com­ plex. This complexity reflects an intri­ cate geologic history and a wide variety of geologic and oceanographic processes that operate on the shelf to transport, erode, and deposit sediment. Data collected from the Continental Slope by the USGS show that the rugged northern part of the Gulf of the Faral­ lones is scarred by numerous small can­ yons. Sediment cover is thin or absent. This northern part contrasts markedly with the southern part of the gulf, which is much less rugged and draped by a thin blanket of sediment. Sediment in the southern part appears stable because no large underwater landslides were dis­ cerned on the sonographs. Conspicuous geomorphic features in the southern part include Pioneer Canyon and Pioneer Seamount. Sediment is accumulating in Pioneer Canyon and on Pioneer Sea- mount, suggesting that this area is depo­ sitional, in contrast to the active trans- port environment found on the shelf. USGS sonographs made of the Gulf of the Farallones have several practical applications. For example, the evidence of strong currents, as indicated by large ripples in coarse sand, suggests that dredge material and pollutants disposed of at sites on the Continental Shelf could be redistributed over large areas. Also, commercial fisherman can use these images to locate the substrates preferred by bottom fishes and crabs. 

of the Gulf of the Farallones 
To w f ish 

Sidescan Sea bottom 

e, a sidescan

ulled behind 

ad swath 

n combined, 

descan-sonar 

f large areas 

he mosaic 

sions (dark 

d ripples east 

ds between 

Golden Gate, 

ght shows 

x bedforms, 

and moving 

0 

0 

0 

0 

Lines are ship’s tracks 

THE SEA FLOOR USING SIDESCAN SONAR 

swath 

400 METERS 

1,300 FEET 

400 METERS 

1,300 FEET 

Landscape of the Sea Floor 17 
Sea bottom 

Sonar beam 

ve, a hull

eam sonar 

g a continuous 

oor as the 

mple profile at 

a submarine 

rugged sea

 typical of the 

e Farallones. 

Ship’ s track 

0 

0 

0 

0 

G THE SEA FLOOR USING NARROW-BEAM SONAR 

NARROW-BEAM-SONAR PROFILE 

500 METERS 

1,650 FEET 

165 FEET 

50 METERS 

of the Gulf of the Farallones 
Three-dimensional bathymetric map of the Continental Slope in the Gulf of the Farallones. This image was created using sonar. 

Landscape of the Sea Floor 19 
y of the Gulf of the Farallones 

erns Over the Continental Shelf and Slope


Farallones 

rnia coast 

rd to Año 

coastal 

ical, rec

cational 

ide living 

anisms. 

s, in the 

n the Far

 from the 

pools to the 

ive in these 

lso a play

s and visi

and com

an integral 

on. 

ocean phe

at the sea 

exposed 

largest cur

ve water 

 Golden 

ing spring 

 Small sail

have trou

 the Golden 

itical. Out

astal ocean, 

e coastline. 

They diminish offshore, becoming overwhelmed by steadier currents as water depth increases. 

Tidal currents and waves are important 

in the coastal ocean. They mix the water column, allowing nutrients near the seabed to reach plants growing in the lighted surface regions. Tides move nutrients and other suspended materials vertically and back and forth, but they generally do not transport these materials large distances. 

On the Continental Shelf and Slope 

in the Gulf of the Farallones oceanic currents flow through the area transporting suspended sediment, nutrients that allow plants to grow, and possible pollutants. Until recently, however, not much was known 

about how strong the currents are, in what direction they flow, or how rapidly flow patterns change with time or location. Even 

less was known about how current patterns 

affect the many creatures that live in the coastal ocean, how currents modify the natural sediment on the sea floor, or about the eventual fate of natural sediment or materials dumped in the gulf. Knowledge is needed about these important factors so that people can make reasonable decisions about how to manage the coastal waters, ensuring that recreational and commercial activities do not harm the environment. 

During the 1990’s, several programs 

were undertaken by the U.S. Geological Survey and other organizations to gather 

information about how currents, nutrients, and suspended material move through the Gulf of the Farallones. The area studied by the USGS covers about 1,000 square nautical miles of the gulf and ranges in water depth from 660 to 10,500 feet. These studies showed that the general features of the complex current patterns in the area are similar to those observed elsewhere along the central and northern California continental margin. 

Currents over the Continental Shelf 

tend to flow southeastward and slightly offshore in summer, causing nutrient-rich cool waters to upwell onto the shelf. Shelf currents flow mostly northwestward in winter. Tidal currents are strong over the 

shelf and tend to be the dominant features in flow patterns near the shoreline or within estuaries. The strong waves that occur during winter storms commonly cause sediment on the sea floor to be resuspended and carried both along and off the shelf. 

The currents on the Continental Slope 

flow dominately northward in all seasons. Tidal currents over the slope are weak except for regions near the seabed or 

within the conspicuous submarine canyons that cut into the continental margin. 

However, many of the current patterns 

in the Gulf of the Farallones are altered by the region’s unique sea-floor topography; 

therefore, the local characteristics of flow, 

such as the amplitude of currents, their detailed response to winds, and the strength of the summer upwelling, are specific to an area. In summer, the promontory of Point Reyes causes shelf currents 

to turn offshore and flow over the slope. 

The abrupt steepening of the slope in the northern part of the area studied also causes northwestward-flowing slope currents to turn toward the deep ocean. Both 

of these features enhance the exchange of water, nutrients, and other suspended materials among the shelf, slope, and deep ocean relative to what happens along the simple, straight shelf more common north of the gulf. 

The complex current patterns in the 

Gulf of the Farallones help to make the coastal waters of the area a truly unique resource. Knowledge of these patterns is essential if competing demands on this resource are to be balanced. 

of the Gulf of the Farallones 
The California Current is part of a permanent, oceanwide gyre in the surface waters of the North Pacific. It 

forms the east part of this gyre, which is defined in the west by the Kuroshio Current (Pacific Gulf Stream), in the north by the North Pacific Current, and in the south by the North Equatorial Current. In the Gulf of the Farallones, currents over the Continental Slope are quite distinct from the southeastward-flowing water of the California Current farther offshore. These slope currents are confined to a relatively narrow band seaward of the Continental Shelf and flow northwestward, parallel to the topography, as the California Undercurrent. In the gulf, the undercurrent is generally found over the slope in water depths less than 2,600 feet. Bathymetry in meters (1 m = 3.281 ft). 

an

Francisco

San Francisco 

 Downwelling warm surface water Wind from south 

8 

37°N 

124°W 122° 

35° 

10 50 

55 60 

12 14 16 

°C °F 

SURFACE WATER TEMPERATURE San Francisco 

Monterey 

Current Patterns Over the Continental Shelf and Slope 

Strongly reversed conditions, common during El Niños 

ds blowing 

 the Corio

and currents 

n Hemi

hern Hemi

 from the 

nutrient

ace in 

the yearly upwelling that makes the ocean off northern California so cold in spring and summer and the Gulf of the Farallones so biologically productive. When El Niño atmospheric phenomena occur, they disrupt this pattern and cause downwelling, which prevents the replenishment of nutrients to surface waters and can have a major impact on sea life. For example, in 1997–98, thousands of seals and sea lions starved to death when 

downwelling warm water drove away many of the fish and squid on which they normally fed. Young animals, such as the sea lion pup shown here, were particularly vulnerable. Areas of 

cold, upwelled water (blue) along the central California coast are shown in the satellite image below (NOAA AVHRR satellite data, processed at Naval Postgraduate School). 

June 18, 1989 

ATER MOVEMENTS AND WINDS OFF THE NORTHERN CALIFORNIA COAST 

21

One method the U.S. Geological Survey has used to 

measure ocean currents in the Gulf of the Farallones is strings of instrument packages attached to mooring lines anchored on the sea bottom. Surface moorings are mainly used in shallower water. Photograph below shows a current meter with an attached transmissometer (instrument to measure water clarity) being lowered into the waters of the gulf. Inset shows surface mooring (float) used for a bottom-anchored string of intrument packages. 

STRINGS OF INSTRUMENT PACKAGES ARE USED TO MEASURE OCEAN CURRENTS 

of the Gulf of the Farallones 
tographs were taken from a U.S. Geological Survey instrument station 

 the sea floor in the Gulf of the Farallones. Strong bottom currents can 

d ripples (left), and weaker currents can leave a smooth sea bottom 

 a curious seal). 

Current Patterns Over the Continental Shelf and Slope 23 
y of the Gulf of the Farallones 

the Sea Floor


floor to be a 

 to a sandy 

ea floor 

y beach 

nd muddy 

dy plains of 

s different 

much of the 

allones. 

l of sedi

ea floor 

particles 

easing 

s model, 

blanket of 

ndy shore— 

y silt and 

This model 

t the energy 

decreased 

 water and 

les could 

ss ener

d on very 

ata led sci

p ocean 

amples had 

no direct 

onsisted of 

yer of finegrained sediment. As sampling tech­ niques improved and more information was collected, scientists learned that the ocean bottom is as texturally varied and morphologically complex as the land surface. The physical characteristics (for example, size, shape, composition) and the distribution of sediment are the result of a complex interaction among geologic, oceanographic, and biologic processes. Moreover, scientists know that the distribution of sediment on the Continental Shelf is made more complex by deposits of relict sediment. Relict sediment is that material, gener­ ally coarse sand and gravel, left on the shelf when it was exposed during times of lower sea level. Evidently, then, the distribution of different types and grain sizes of sed­ iment and rocks provides clues about the geologic history of an area and the types of ocean currents that deposited or reworked the sediment. Moreover, the different substrates provide habitats for the various organisms that live on, in, and near the sea floor. Information about substrates in Gulf of the Farallones National Marine Sanctuary is used by scientists investigating biodiversity and ecologic systems to help understand and manage the variety of animals and plants that live in the sanctuary. Such informa­ tion is also used by commercial fisher- men as an aid for locating fishes and crabs that prefer a particular substrate. The sea floor in the Gulf of the Farallones consists of many different types of substrate, including rock out- crops, gravel, sand, clay, and deposits of broken shells. Some of these different types of substrate are found very close to each other and have abrupt boundar­ ies between them. On the Continental Shelf a wide corridor of sand extends westerly from the Golden Gate to the Farallon Islands. Silty sand and sandy silt bound the corridor to the northwest and southeast, and a band of silt extends around Point Reyes. In general, the sediment on the sur­ face of the Continental Slope is finer and more uniform than that on the Con­ tinental Shelf in the Gulf of the Faral­ lones. Nonetheless, most of the surficial sediment on the Continental Slope in the area of the Gulf of the Farallones stud­ ied is very sandy, a condition that is unusual (continental slopes are gener­ ally characterized by silt and clay). The reason for this abundance of sand is not fully understood. In general, excep­ tionally strong currents are required to transport large amounts of sand from the shelf to the slope, but such situations are extremely uncommon. It is not yet known whether the textural patterns and bedforms on the Continental Shelf in the Gulf of the Farallones reflect entirely present-day processes or whether some of these fea­ tures are remnants of processes that operated during lower stands of sea level in the past. During the glacial cycles of the past several million years, sea levels were lowered to as much as 445 feet below present-day sea level. Therefore, ancient relict features created during lower stands of sea level are common on Continental Shelves worldwide. Such lowstands of sea level would have exposed virtually all of the shelf in the Gulf of the Farallones. 

of the Gulf of the Farallones 
5 6 7 8

0 1 INCH

0 2 CM

0 1 INCH

0 2 CM

0 1 INCH

0 2 CM

0 1 INCH

0 2 CM

Samples and photographs of the sea floor in the Gulf of the Farallones collected by the U.S. Geological Survey reveal a variety of substrates, including rock outcrops, gravel, sand, clay, and deposits of broken shells. Some of these different types of substrate are found very close to each other, and the boundaries between them are abrupt. In general, surficial sediment on the Continental Slope in the gulf is finer and less varied in composition and texture than that on the Continental Shelf. This map shows sediment size distribution on an area of the shelf to the northeast of the Farallon Islands. 

Sediment of the Sea Floor 25 
y of the Gulf of the Farallones 

mposition of Surface Sediments on the Sea Floor


ner 

ea floor in 

h a few 

elp deter

n of these 

were taken 

 at sites on 

shelf down 

00 feet. 

for 28 major 

rbon, and 

 the history, 

ediments in 

uding the 

l fluctua

e Continen

as a low 

nd water 

0 feet to 

al Slope in 

gradient of 

th reaches 

lthough the 

canyons, 

 numerous 

, including 

he main 

f of 

 onshore 

mentary, 

metamorphic, and igneous rocks. About 500,000 years ago, drainage from interior California broke through to the Pacific Ocean at the Golden Gate, providing additional sources of sediment from as far away as the Sierra Nevada. The Continental Shelf between the Golden Gate and the Farallon Islands is covered with 

sandy sediment, which has been repeatedly reworked by fluctuations in sea level 

and great (100-year) storms. Major lowerings of sea level during global glaciations have exposed the shelf in the gulf as dry land several times, most recently from about 20,000 to 15,000 years ago. In these glacial periods, sea level was lowered by 

hundreds of feet, because of the large amount of water tied up in ice sheets on land. During these lowstands, a river probably coursed across all of what is now the Continental Shelf in the gulf, although no channel has yet been identified. About 15,000 years ago, rising sea level caused by the melting of the ice sheets once again drowned the Continental Shelf. 

Water movement in the Gulf of the Farallones affects the distribution of sediment 

on the sea floor and the movement of sediment across the Continental Shelf to the deep sea (see chapter on Current Patterns over the Continental Shelf and Slope). 

The main oceanographic influences on circulation in the gulf include the southward-flowing California Current during 

the winter and the northward-flowing California Undercurrent during the summer. Strong offshore currents can also be caused by summer northwesterly winds, leading to coastal upwelling of cold water. Currents generated by tides also help account for the seaward transport of sediment in the gulf. 

The results of chemical analysis of the 

core samples collected from the sea floor in the Gulf of the Farallones can be used as “fingerprints” to identify sources and transport patterns of sediment (see chapter on Heavy-Mineral Provinces on the Continental Shelf). The sandy sediments on 

the Continental Shelf between the Golden Gate and the Farallon Islands contain abundant heavy minerals that are rich in iron, magnesium, titanium, phosphorus, and many trace elements. The sediments immediately adjacent to the Farallon Islands contain low concentrations of heavy minerals and the chemical elements associated with them; instead, these sediments are rich in silica (SiO2). Sediments 

deposited on the Continental Slope have higher contents of organic matter and clay and, consequently, have higher concentrations of elements associated with clay minerals, such as aluminum, lithium, potassium, and sodium. Calcium carbon- ate (CaCO3), mainly from the shells of pelecypods (oysters, clams, and mussels), is a very minor constituent of surface sedi­ ments in the gulf. 

of the Gulf of the Farallones 
0.6 

0.

4 

0.8 

0.4 

0.2 

0.2 

0.4 

0.4 

0.4 

0.6 0.8 1.0 

1.2 

3.0 

1.4 

1.8 

2.

4 2.2 

123°20'W 123°00' 122°40' 

Farallon 

67 68 

74 

71 

71 

0 

72 

73 69 

69 

67 

69 

123°00' 122°40' 

allon 

Sample site Contours of 

organic-carbon content (weight percent) 

0.2 Sample site Contours of 

silica content 

(weight percent) 

66 

The content of organic carbon (carbon from the remains of organisms) in sea-floor sediments from the Gulf of the Farallones is relatively high for an area of ocean adjacent to a continent, reflecting the high biologic productivity supported by the nutrient-rich seasonal upwelling of the California Current system. The finer-grained sediments on the Continental Slope in the gulf have higher contents of organic carbon than the mostly sandy sediments on the Continental Shelf. 

inental Shelf in the Gulf of the Farallones have high contents of silica 

e Farallon Islands, where granitic sand has been shed from the islands. 

s lower on the Continental Slope, because the clay minerals making 

 there are lower in silica. The higher silica content in sediments on the 

p probably reflects sand moving down Pioneer Canyon. 

CONTENT OF SILICA AND ORGANIC CARBON IN SEA-FLOOR SEDIMENTS 

Islands Islands

Chemical Composition of Surface Sediments on the Sea Floor 27 
y of the Gulf of the Farallones 

ral Provinces on the Continental Shelf


aspect of 

easing gem 

ssential 

ology, min

certain 

rge bodies 

e), how do 

rocesses), 

ibution). 

ologic 

ones 

) mineral 

(“heavy 

erals at 

ater). Small 

d great dis

 contrast, 

ansported 

depositional 

nostic as 

ll particles 

ues to sedi

stribution. 

 extends 

h to Año 

the Golden 

ntinental 

e beyond 

Bank ridge. 

generally 

 gulf lies 

west of the major tectonic feature known as the San Andreas Fault Zone, which separates two different types of basement rock: granitic rocks of the Salinian block on the west, and various sedimentary, volcanic, and metamorphic rocks of the Franciscan terranes to the east (see chapter on Earthquakes, Faults, and Tectonics). 

The surficial sediment in the Gulf of 

the Farallones was initially eroded from rocks onshore and then transported and deposited in the present offshore basin. The agents of this process included faulting and folding of the Earth’s crust and changes in global climate, including glaciation. The sediment of the sea floor in the gulf (see chapter on Sediment of the Sea Floor) is composed of sand, mud, some gravel, and biologic debris, such as 

shells and bone fragments. 

Sediment on the Continental Shelf in 

the Gulf of the Farallones west of San Francisco Bay was systematically sampled by the U.S. Geological Survey in 1989 to study its characteristics, distribution, and origin. Various properties of the samples were analyzed, including grain size and mineralogic and chemical composition (see chapter on Chemical Composition of Surface Sediments on the Sea Floor). The minerals present in the samples reflect two major sources in the central California region: (1) the large variety of rock types of the Franciscan terranes and (2) granitic materials shed from the Sierra Nevada and similar rocks in the central California region. The two mineralogical assemblages are distrib­ uted in different areas of the shelf; how this distribution developed is less clear. The mineral and chemical composi­ tion of sediments from the Gulf of the Farallones define four depositional prov­ inces—two that are composed of granitic debris and two that reflect sources in the Franciscan terranes of northern Califor­ nia. The granitic sediment comes from two sources. The dominant source is the Sierra Nevada. The sediment from this source was transported down the Sacra­ mento-San Joaquin drainage and through San Francisco Bay and the Golden Gate. The lesser source is the granitic base­ ment rocks of the Salinian block west of the San Andreas Fault system. Sediment from a Sierran source is spread over the Gulf of the Farallones to a limited extent north of the Golden Gate and to at least the shelf edge south of the Gate. A small contribution of sediment from Salinian rocks of the Farallon Islands- Cordell Bank ridge, along the west edge of the shelf, is also found on the shelf near the ridge. Minerals derived from the Franciscan terranes characterize surface sediment on the Continental Shelf in the northern Gulf of the Farallones. These minerals represent reworked shelf deposits, ero­ sion of dune deposits accumulated during the last low stand of sea level, and coastal erosion of Franciscan bed- rock exposures. 

of the Gulf of the Farallones 
amples of 

 the Faral

ple consisting 

Sample con

avy as water) 

 of the miner

nite, a clay 

—hypersthene 

glass slide for 

 light. D, The 

d light. The 

 of illumina

Map of the Gulf of the Farallones, showing sites where the U.S. Geological Survey collected bottom-sediment samples for mineralogical analysis. Grains of fine and 
very fine sand (about 0.002 to 0.010 inch in diameter) were separated and then divided into “light” minerals (less than 2.96 times as heavy as water) and “heavy” 
minerals (more than 2.96 times as heavy as water). Numbers on the map show the abundance of heavy minerals as a percent of sample weight, and the sizes of the 
shaded boxes are proportional to this abundance. The thick blue line marks the approximate boundary between areas covered by different heavy-mineral assemblages. 
The mineralogy and geochemistry of sediments from the Gulf of the Farallones define two main depositional provinces—one composed of granitic debris and one that 
indicates a source in the Franciscan terranes of northern California. The granitic sediment comes from two sources. The dominant source of granitic sediment is the 
Sierra Nevada. The sediment from this source was transported down the Sacramento-San Joaquin drainage and through San Francisco Bay and the Golden Gate. 
The lesser source of granitic sediment is the basement rocks of the Salinian terranes west of the San Andreas Fault system, including the Farallon Islands. Minerals 
derived from the Franciscan terranes characterize surface sediment on the Continental Shelf in the northern Gulf of the Farallones. These minerals represent reworked 
Continental Shelf deposits, erosion of dune deposits accumulated during the last lowstand of sea level, and coastal erosion of Franciscan bedrock.


Heavy-Mineral Provinces on the Continental Shelf 29 
ds of people are attracted to the cold waters of the Gulf of the 

hale and bird watching, beautiful coastal tide pools, and com

shing. Few realize that the organisms that they see and catch are 

 a rich and complex marine ecosystem. 

und that the distribution and abundance of marine flora and fauna 

tly related to the physical and chemical conditions of its waters. 

nutrient-rich waters along the coast during the spring and summer 

rs feeds microscopic plankton that support a complex but fragile 

rom Dungeness crabs, chinook salmon, and brown pelicans to 

t white sharks, and giant blue whales. The Cordell Bank, Gulf of 

Monterey Bay National Marine Sanctuaries help to protect and 

e abundance. 

ches in the Gulf of the Farallones 

on 

th 

n the marine 

lones. 

d plants are 

nearshore 

he upper 

he name 

o Greek 

 and “wan

o major 

ast-growing 

to propel 

nd (2) 

which can 

column in 

xhibits a 

es, many 

mentations. 

n are at the 

ansport to 

survival and 

es can play a 

he distribu

Rapid cell 

 in phyto

of cells per 

sible blooms 

high produc

hytoplankton 

arine food 

 the diversity and abundance of marine life in the Gulf of the Farallones would be impos­ sible. Phytoplankton provide food for a tre­ mendous variety of organisms, including zooplankton (microscopic animals), bivalve molluscan shellfish (mussels, oysters, scal­ lops, and clams), and small fish (such as anchovies and sardines). These animals, in turn, provide food for other animals, including crabs, starfish, fish, marine birds, marine mammals, and humans. The coastal area of the Gulf of the Far­ allones undergoes periods of strong upwell­ ing during the spring and summer months (see chapter on Current Patterns over the Continental Shelf and Slope). In addition to delivering colder, nutrient-rich waters from depth, coastal upwelling concentrates phy­ toplankton near the surface. This concen­ tration of cells in sunlit surface waters, together with increased nutrients, may pro- vide a competitive edge for the faster grow­ ing diatoms during upwelling events. Con­ versely, a stratified water mass consisting of a layer of warmer surface water and a deeper layer of colder, nutrient-rich water can form following upwelling. These con­ ditions favor the development of dinofla­ gellate blooms, such as toxic “red tides,” because these types of phytoplankton can actively swim to the surface to photo- synthesize during the day and migrate to deeper areas at night to absorb nutrients. Such conditions can also be associated with downwelling, in which warmer off- shore waters move shoreward, pushing coastal surface waters down and along the sea floor to deeper areas. Research in other parts of the world has shown that dino­ flagellates are commonly associated with such nearshore downwelling. Of the more than 5,000 known species of marine phytoplankton, approximately 40 species worldwide have been linked with production of toxins. These marine biotox­ ins can have subtle to lethal effects on various forms of marine life. Human con­ sumers of certain seafood items (especially clams, oysters, and mussels) are also at risk. It remains difficult to avoid the harm­ ful effects associated with blooms of these toxic species because phytoplankton ecol­ ogy is not fully understood. Within the Gulf of the Farallones, red tides are a common natural phenomenon, usually occurring from August through October, when a relaxation of coastal upwelling results in a warmer, more stable water mass nearshore that appears to favor dinoflagellate populations. The commonly used term “red tide” is misleading, because phytoplankton blooms frequently are other colors, such as brown, green, and yellow, and are in any case not a tidal phenomenon. Nearly all phytoplankton blooms along the California coast and within the Gulf of the Farallones involve nontoxigenic spe­ cies. Conversely, most incidents of paralytic shellfish poisoning (PSP) in humans caused by eating shellfish caught in California waters have occurred in the absence of vis­ ible blooms of toxin-producing phytoplank­ ton. Because the coastal area encompassed by the marine sanctuary has been the focal point for PSP toxicity in California, and because of the continued increase in com­ mercial bivalve shellfish aquaculture within this area, the California Department of Health Services has intensified its biotoxin­ monitoring efforts in the area. The key to understanding the combina­ tion of physical, chemical, and biological factors that result in blooms of the phyto­ plankton species that produce PSP toxins may lie within the Gulf of the Farallones. Such understanding would greatly assist in the protection of public health. 

es in the Gulf of the Farallones 
PLIFIED DIAGRAM OF THE FOOD WEB IN THE GULF OF THE FARALLONES 

Marine birds 

Humans 

Humans 

Mussels Phytoplankton 

Scallops Clams Anchovies Starfish Large fish Sharks 

Oysters Zooplankton SardinesCrabs 

Seals 

Without phytoplankton, the diversity and abundance of marine life in the Gulf of the Farallones would be impossible. Phytoplankton provide food for a tremendous variety of organisms, including zooplankton (microscopic animals), bivalve molluscan shellfish (mussels, oysters, scallops, and clams), and small fish (such as anchovies and sardines). These animals, in turn, provide food for other animals, including crabs, starfish, fish, marine birds, marine mammals, and humans. 

Phytoplankton 33 
Photographs of diatoms taken through a microscope. 

Coscinodiscus (left) and the chain of Chaetoceros (right) are centric diatoms. Pseudonitzschia (bottom) produces domoic acid, which can contaminate shellfish and cause “amnesic shellfish poisoning” in 

humans who eat the shellfish. Symptoms include abdominal cramps, vomiting, disorientation, memory loss, and even death. Scale bars are in micrometers (μm); 1 micrometer is one-millionth of a meter or about 1/25,000 of an inch. 

es in the Gulf of the Farallones 
Photographs taken through a microscope of the 

armored dinoflagellates Ceratium (left), Dinophysis (right) and Alexandrium catenella (bottom). Some species of Dinophysis produce toxins that can cause severe diarrhea (diarrhetic shellfish poisoning) in humans who eat contaminated shellfish. Alexandrium catenella produces toxins that can cause “paralytic shellfish poisoning” in humans who eat contaminated shellfish. Symptoms include nausea, vomiting, diarrhea, abdominal pain, and tingling or burning lips, gums, tongue, face, neck, arms, legs, and toes and later shortness of breath, dry mouth, a choking feeling, confused or slurred speech, lack of coordination, and even death. Scale bars are in micrometers (μm); 1 micrometer is one-millionth of a meter or about 1/25,000 of an inch. 

Phytoplankton 35 
ches in the Gulf of the Farallones 

s on land, 

the ocean as 

es, the grow

g, when the 

e increase of 

fuel growth 

od web. In 

he world, 

alled “krill,” 

is early-sea

 link in the 

ytoplankton 

ooplankton 

nd and by 

mals, trans

mary pro

s of the 

n referred 

e they play 

nctioning of 

 eggs and 

stages before 

pment pro

asting off the 

ts growth), 

ndages are 

outside skel

n increase 

he unique 

fter a molt 

if food resources are scarce. Because krill can increase and decrease their size, it can be difficult to determine their age or the age distribution of a population of animals from their sizes. 

Krill have legs called “swimmerets” that 

have evolved to look like small feathers and 

function like fins, giving them great mobility 

and agility for life in the water column. They 

feed while swimming, using their modified front legs to form a food basket that strains food from the water while they swim. 

Krill are typically very gregarious, which 

means they are often found in large, concentrated groups, including dense swarms with as many as 100,000 krill per cubic yard of ocean water. This swarming behavior makes krill especially vulnerable to predators. Swarming activity starts sometime in spring and continues through the fall. These aggregations can commonly be located in the Gulf of the Farallones by finding flocks of diving seabirds or clusters of birds picking at the surface. Fishermen use these feeding flocks to help them locate salmon feeding on the undersides of the krill swarms. Lunging humpback whales that break the surface of the water are also a good indication that krill are swarming at or near the surface. Surface swarms provide ideal feeding conditions for these large filter feeders. With its 

huge mouth, a gaping humpback (and other baleen whales) is capable of engulfing a large volume of krill in a single gulp. These dense aggregations of prey provide the several tons 

of food per day required by these whales during the summer feeding season. 

In the Gulf of the Farallones, the two most 

abundant species of krill are Thysanoessa spinifera and Euphausia pacifica. They are typically about 3/4 inch long and live for about 2 

years. Thysanoessa spinifera is found mostly 

in shallower water over the continental shelf, whereas Euphausia pacifica is usually found in deeper water towards the margin of the 

shelf and beyond. Between them they are a major food source for salmon (krill pigments give salmon flesh its characteristic pink to orange color), rockfish, seabirds, and whales. Krill are the main reason hungry humpback and blue whales visit the gulf in the summer—to fatten up for the rigors of the coming year. Both of these krill species demonstrate special adaptations that enable them to succeed despite constant predation pressure. From spring through fall, Thysanoessa spinifera swarm at the surface during the 

day. Though it is unclear what is driving this behavior, the benefits must outweigh the cost, 

which is increased predation. 

Euphausia pacifica, controlled by light 

intensity, migrate out of ocean depths and 

into surface waters each night. As dawn approaches, they return to deep water for 

the day. This migration pattern is shared with many other organisms in the ocean, and during the day krill form part of the so-called “deep scattering layer” that fishermen see on their depth sounders. The timing of this daily event in response to changing light intensities provides Euphausia pacifica with several advantages. By moving upward at night, Euphausia pacifica minimizes exposure to daytime predators, while grazing in surface waters where food is abundant. They 

also realize an energy gain by returning during the day to the colder deep water, 

where metabolism slows. Releasing eggs in 

warmer surface waters speeds development 

times, thus reducing the time exposed to predators; it also ensures that hatching larvae are in productive waters when they start feeding, increasing their chances of survival. 

Krill are a critical link in the Gulf of the 

Farallones marine food web and in marine food webs around the world. They directly or 

indirectly support the survival and well-being of many animals living in different oceans. Knowing the key position filled by krill in 

many marine ecosystems, we need to ensure that their populations remain healthy—for the well-being of all. 

es in the Gulf of the Farallones 
1 CENTIMETER 

0.5 INCH

Sample of plankton collected in the Gulf of the Farallones, showing several euphausiid shrimp (krill) and numerous other zooplankton. (Photograph courtesy of Jamie Hall.) 

Krill 37

Gulf of the 

 photograph 

noessa spi

he Farallones 

1 CENTIMETER 

0 0.5 INCH0 

1 CENTIMETER 

0 0.5 INCH0 

es in the Gulf of the Farallones 
Lunging humpback whales feeding on surface 

swarms of krill are a common sight in the Gulf of the Farallones in the summer. (Photograph courtesy of Thomas R. Kieckhefer, Pacific Cetacean Group.) 

Seabirds feeding on swarming krill in the Gulf of the Farallones. (Photograph from Gulf of the Farallones National Marine Sanctuary.) 

Krill 39

ches in the Gulf of the Farallones 

g Larvae of Crabs, Sea Urchins, and Rockfishes


welling 

tant role in 

arallones and 

y species, 

Free-floating 

ns by 

 are dis

rnia coast. 

vertebrates 

abs) and 

up of a net

read along 

solely by 

 many com

cies, such 

gister), red 

francisca

p.), have 

ft as plank

vae are 

nd south

rnia Current 

ling season 

s Over the 

Understand

 maintain 

ransported 

abitat is 

term viabil

In 1992, a study was begun to understand 

how coastal oceanographic processes influence the distribution of crab and sea-urchin larvae around Bodega Head, a coastal headland at the northern margin of the gulf. This required the cooperative efforts of many organizations, including Gulf of the Farallones and Cordell Bank National Marine 

Sanctuaries, U.S. National Marine Fisheries Service, Scripps Institution of Oceanography, Point Reyes Bird Observatory, Oregon 

State University, California Department of Fish and Game, and Pacific Fisheries Environmental Group. 

Sampling extended over several years 

and was done both from aboard ships and at shore stations. Results indicate that during periods of upwelling, larvae accumulate in the warm water that collects between the 

Farallon Islands and Point Reyes in the northern gulf. Larval accumulation was also observed in the upwelling shadows, or 

eddies, that form behind other capes and headlands when the wind is blowing from the north and surface water is moving in a southerly offshore direction. When the northerly winds that cause upwelling relax, this larvae-rich water moves north in buoyancy-driven currents that remain coastally trapped. During this time many larvae that have been retained in the gulf are transported to the north, and some settle out of the water column and onto the sea floor for their next life stage. In both 1994 and 1995, an upwelling jet seaward of Point Reyes and an upwelling shadow downwind (south) of the point were evident from the currents, temperature, and salinity of the surface waters. Information was collected at the boundaries between four distinct water masses: (1) newly upwelled water, (2) oceanic water from offshore, (3) San Francisco Bay outflow, and (4) a mix­ ture of these water types that was called “gulf water.” The different water masses con­ tained different types of larvae. In general, all stages of larval development for crabs of several species could be found within, but not outside, the gulf water. This water mass is found in the wind shadow south of Point Reyes. In contrast, rockfish larvae were found in high concentrations offshore in oce­ anic water and at the boundary between newly upwelled water and gulf water. The Gulf of the Farallones provides a pathway along which distinct masses of water con­ taining both crab and rockfish larvae are likely to be transported to suitable juvenile habitats within the gulf and to the north. Larval settlement becomes more epi­ sodic and less frequent with increasing northward movement away from the area of larval retention/accumulation south of Point Reyes. Nearly twice as many crab larvae settle at Point Reyes and to the south, where warmer gulf water is constantly present, than to the north, where settlement occurs only when the northerly winds that cause upwell­ ing subside and relaxation currents move northward. Sea urchin larvae also settle during specific oceanic conditions, but less predictably than crabs. Consistent larval dispersal from any sub- population of adult animals may be limited to the length of an embayment. For example, two such embayments on the northern Cali­ fornia coast are from Point Reyes to Point Arena and from Point Arena to Cape Men­ docino. Because strong seaward currents form at each end of these embayments during upwelling, larvae caught in these cur- rents would be swept out to sea and have no chance of developing and becoming a part of the adult population. The data collected in this study on the distribution of free-floating larvae in the Gulf of the Farallones provide critical infor­ mation on the lifecycles of commercially important bottom-dwelling species. Because these larvae are a food source for many marine species, this information is crucial to the effective management and conservation of coastal marine ecosystems in the gulf. 

es in the Gulf of the Farallones 
1 CENTIMETER 

0.5 INCH

Larval crab from the Gulf of the Farallones, greatly magnified. 

Sample of plankton collected in the Gulf of 

the Farallones, showing a larval rockfish, euphausiid shrimp (krill), and other zooplankton. (Photograph from Gulf of the Farallones National Marine Sanctuary.) 

Red sea urchins, harvested for sushi, are one of 

many commercially important coastal species in the Gulf of the Farallones with swimming larval forms that drift as plankton during the spring. (Photograph from Gulf of the Farallones National Marine Sanctuary.) 

Free-Floating Larvae of Crabs, Sea Urchins, and Rockfishes 41 
ches in the Gulf of the Farallones 

ok salmon 

nd coho 

monly found 

hinook 

at brings the 

of the gulf. 

the gulf was 

n. 

re key pred

ribution and 

seasonal 

on found in 

urning from 

ng to enter 

where they 

the eggs 

 juvenile 

 in freshwa

cean, where 

e returning 

mon along 

as a threat

ered Spe

been pro

 (versus 

also a candi

sting. 

from the 

 of the Far

, when they 

from Bolinas Point in the north to Point San Pedro in the south. While in this area they feed almost equally on Pacific herring and anchovies. The herring have just migrated back to their feeding grounds outside of the Golden Gate from San Francisco Bay, where they spawned from November through February, and anchovies are gath­ ering in nearshore waters before moving into the bay beginning in April. In April, chinook salmon are found from north of the Golden Gate to Point Reyes and offshore to the Farallon Islands. There they feed on invertebrates, largely the euphausiid shrimp (krill) Thysanoessa spinifera. Krill are taken as prey from surface and subsurface swarms that occur over a wide area of the gulf during April and May. The pink to orange color of salmon flesh during this period is due to a carotenoid pigment in the exoskeleton of the krill (for more information, see chapter on Krill). This flesh color has become so popular that now there are fisheries for krill, which are freeze-dried and fed to pen-reared salmon as a finishing product to produce this color. For a brief 2- or 3-week period in April, the chinook’s diet is dominated by the megalopa larvae of the Dungeness crab (Cancer magister) (see chapter on Free- Floating Larvae of Crabs, Sea Urchins, and Rockfishes). These larvae are the last pelagic (free-floating or swimming) stage before the crabs sink to the bottom and take on their adult shape. More than 7,000 Dungeness megalopa have been found in a single chinook-salmon stomach. In May and June, chinook start feeding on krill and juvenile rockfish offshore near the Farallon Islands. These rockfish are late pelagic-stage fish that as adults will migrate to bottom habitats. In years when juvenile rockfish are abundant, they are the preferred prey and dominate the chi- nook diet during these months, whereas in low-abundance years, chinook salmon feed mainly on krill. Sometime between mid-June and mid- July, the chinook salmon abruptly move from near the Farallon Islands to directly in front of the Golden Gate, the so-called “middle grounds.” Here, chinook salmon feed exclusively on anchovies, which had moved into San Francisco Bay in May and June to begin spawning in the warmer water. After June, when the water in the gulf warms up because of the absence of cold upwelled water, anchovies move out of the bay and into the gulf where they continue spawning into October. Chinook Salmon remain in front of the Golden Gate until October, but in lower and lower concentrations as they move up the Sacra­ mento River system to spawn. The follow­ ing February, the next year’s 3-year-old chinook salmon begin to enter into the gulf, and the cycle begins again. During strong El Niño years, the normal sequences of chinook salmon prey do not develop because the large increase in ocean temperature disrupts the prey’s normal behavior. As a result, the aggrega­ tions of salmon that feed on these prey do not form, and chinook salmon of a given length weigh much less than normal. California’s commercial salmon catch also drops severely, and the recreational catch is far below average. 

es in the Gulf of the Farallones 
0 10 KILOMETERS 

0 10 MILES 

SAN 

FRANCISCO 

Bolinas 

Point 

San Pedro 

San Pablo Bay 

S A N 

F R A N C I S C O

B A Y 

°00'W 122°30' 

Anchovies 

Anchovies 

Pacific herring 

 larvae 

March 

February 

k salmon 

June 

July through October 

To Sacramento River 

April 

As shown in this simplified diagram, 3-year-old chinook salmon returning from the open ocean move into the Gulf of the Farallones in February and March and feed on Pacific herring and anchovies off the Golden Gate from Bolinas Point in the north to Point San Pedro in the south. In April, they feed on invertebrates, largely the euphausiid shrimp (krill) Thysanoessa spinifera. For a brief 2- or 3-week period in April, the chinook salmon’s diet is dominated by larvae of the Dungeness crab (Cancer magister). In May and June, chinook salmon start feeding on krill and juvenile rockfish near the Farallon Islands. Sometime between mid-June and mid-July, chinook salmon abruptly move from near the Farallon Islands to directly in front of the Golden Gate, the so-called “middle grounds.” Here, chinook salmon feed exclusively on anchovies. Chinook salmon remain in front of the Golden Gate until October, but in lower and lower concentrations as they move up the Sacramento River system to spawn. The following February, the next year’s 3-year-old chinook salmon begin to enter into the gulf, and the cycle begins again. 

Chinook salmon fishing is the activity that brings the 

tshawytcha). Most chinook salmon found in the Gulf of the Farallones are 3-year-old fish that are returning most people out on the waters of the Gulf of the 

g to enter the Sacramento River system, where they will spawn and then die. (Photograph from U.S. Food Farallones. This large salmon was caught in the gulf. 

(Photograph from National Marine Fisheries Service.) 

Salmon 43 
ches in the Gulf of the Farallones 

f the Faral

study. Resid

he most 

ed by land

erally nest in 

ting research 

s and nest

ns, seabirds 

s of the 

s observa

idely varying 

nteresting 

erm but 

dgepodge of 

n common 

he ocean. 

e are 11 

s, including 

inoceros 

d pelagic 

n guillemots, 

ecies of 

ors to the 

ples of 

red-throated 

ebes, black

ller’s, and 

g and glau

d surf sco

of nonbreeding seabirds have been recorded rarely or as vagrants in the gulf, including the manx shearwater, an Atlantic species that has recently been seen sporadically and could even begin to breed in the gulf. All of the breeding species in the Gulf of the Farallones nest on the Farallon Islands, which are in the center of the gulf. Since 1968, biologists from the Point Reyes Bird Observatory have monitored the size and productivity of these populations. Only through such long-term research can a full understanding of the population dynamics of these species and of their relation to the marine environment be achieved. Some of these species also nest on cliffs and small islets along the Marin County coast, north of the Golden Gate. The common murre typifies breeding sea- birds in the Gulf of the Farallones. Before the 1850’s, an estimated 400,000 to 600,000 murres bred on Southeast Farallon Island, but this population was decimated by egg collect­ ing in the wake of the California Gold Rush, before chickens had arrived in sufficient num­ bers to provide eggs for the burgeoning San Francisco populace. Other threats, such as oilspills, human disturbance on the islands, and the depletion of Pacific sardine stocks, reduced populations further until they reached a low of about 6,000 birds during the 1950’s. Southeast Farallon Island became a National Wildlife Refuge in 1969, and through pro­ tection and increased environmental aware­ ness, populations in the Gulf of the Farallones gradually climbed to about 100,000 individu­ als by the year 2000. Common murres, along with the other seabirds breeding at the Farallones, have “good years” in which 90 percent or more of the pairs successfully fledge a chick, and “bad years” in which failure rates reach 50 percent or more. These good and bad years generally reflect the strength of the California Current, the intensity of coastal upwelling, the pres­ ence and absence of “El Niño” events (see chapter on Current Patterns Over the Conti­ nental Shelf and Slope), and the effects that these processes have on juvenile rockfish, anchovies, sardines, and other food resources. Because of the high levels of marine pro­ ductivity found in the Gulf of the Farallones, many species that nest far away also come to the region during their non-breeding seasons. The most common of these species is the sooty shearwater, which visit the Gulf of the Farallones in late summer by the hundreds of thousands, if not a million or more at a time. Every autumn there is also a great northward dispersal of organisms into the Gulf of the Farallones from the south, follow­ ing the northward migration of the northern anchovy. Among the birds that follow this migration are brown pelicans, Heermann’s gulls, and elegant terns. Many species of loons, grebes, ducks, gulls, and alcids (a family of diving seabirds having a stocky body, short tail and wings, and webbed feet— they include the horned puffin, the ancient murrelet, Xantu’s murrelet, and the threat­ ened marbled murrelet) take up winter resi­ dence in the Gulf of the Farallones, escaping the harsher winters of their Alaskan breeding grounds. Finally, a few species of seabirds breed to the north and winter primarily or entirely to the south of the gulf. These long- distance migrants, including phalaropes, jae­ gers, and Sabine’s gull, can be seen passing through the Gulf of the Farallones from July to October and in April and May. Current threats to seabird populations in the Gulf of the Farallones region include effects of contaminants from San Francisco Bay, overfishing, low-level or “chronic” oil pollution, and mortality associated with gill- netting in Monterey Bay. Declines in some seabird populations in the gulf are occurring because of these and other effects. Data on the reproductive success and survival of these seabirds, integrated with knowledge of food resources and the marine environment, can be used to assess the status and health of the Gulf of the Farallones marine ecosystem. 

es in the Gulf of the Farallones 
The common murre typifies breeding seabirds in the 

Gulf of the Farallones. Before the 1850’s, an estimated 400,000 to 600,000 murres bred on Southeast Farallon Island, but this population was decimated by egg collecting in the wake of the California Gold Rush (see inset, courtesy of the California State Library), before chickens had been brought in sufficient numbers to provide fresh eggs for the burgeoning San Francisco populace. 

Seabirds 45

A tufted puffin eating a small fish. 

Only 50 or 60 of these birds breed on the Farallon Islands each year, in deep rocky crevices within the cliffs. Where these striking birds go in the winter is unknown, evidently somewhere far out at sea. Populations of tufted puffins numbered in the thousands during the 1800’s; recent declines are attributed to a degradation in the marine environment and, possibly, to the disappearance of Pacific sardines in the 1940’s. (Photograph from Gulf of the Farallones National Marine Sanctuary.) 

A South Polar skua, the avian “king of the sea” 

with a 4-foot wingspan, in search of victims in the Gulf of the Farallones. Breeding deep in the Southern Hemisphere, skuas disperse over the oceans during the nonbreeding seasons (summer and fall in the Northern Hemisphere), as far north as the Gulf of Alaska. Skuas are piratic and forcibly extract food from their victims—shearwaters, petrels, gulls, and even albatrosses. They are solitary marauders, nowhere common, but in the gulf they are always a menace to visiting seabirds. 

es in the Gulf of the Farallones 
Western gulls (chick shown below) nesting on Southeast Farallon Island. Populations of western gulls in 

the Gulf of the Farallones since 1950 have benefited from feeding at land-based dumpsites and fish-processing plants, expanding from about 6,000 breeding birds historically to more than 25,000 birds during the early 1990’s. (Photographs from Gulf of the Farallones National Marine Sanctuary.) 

Seabirds 47

ches in the Gulf of the Farallones 

mals 

e Gulf of the 

undance of 

en there. In 

 predators 

cies. Some 

gh the gulf, 

haul out” on 

ung. They 

 of the high 

ters and the 

distributed 

rculatory 

of nutrient

pecies of 

cies that 

c (open 

ale and blue 

dangered 

s listed as a 

ominant spe

white-sided 

 porpoise, 

 seal, north

al. 

ale is 

cetaceans 

s) in the 

rate from 

tic Ocean 

oons of Baja 

California (Mexico), where they give birth to their young. They can be seen migrating southward through the gulf beginning in November, and peak sightings are during January and March. A few juveniles may be seen year round. Gray whales are “baleen” whales—instead of teeth, they have numerous long overlapping strips of elastic fingernail-like material (baleen) hanging from 

their upper jaws that they use to filter out 

food. Gray whales feed primarily on the shallow bottom (less than about 400 feet deep), where they swim on their sides while shoveling up mouthfuls of mud and water to strain out small crustaceans, such as amphipods, and other animals living in the sediment. They also feed in the water column on euphausiid shrimp (krill) and a few fish species, such as herring. 

Humpback whales are the most acrobatic of the baleen whales seen in the gulf. 

They use the gulf and Cordell Bank to the north as feeding grounds during the summer and fall months. Their prey consist primarily of the krill species Thysanoessa spinifera and Euphausia pacifica, and they also feed on schooling fish, such as herring, juvenile rockfish, and anchovy. 

Blue whales migrate to the Gulf of the 

Farallones during the late summer and are found there throughout the fall. As adults, 

these giant whales generally weigh more than 100 tons and may be the largest animals that ever lived on Earth, possibly 

exceeded only by the dinosaur Ultrasaurus. These baleen whales feed primarily on krill and, infrequently, red pelagic crabs. Red pelagic crabs are found in the gulf only during warmer-water conditions, such as 

occur when El Niño events affect the gulf (see chapter on Current Patterns Over the 

Continental Shelf and Slope). 

The most familiar of the pinnipeds (seals 

and sea lions) in the gulf is the California sea lion. During its nonbreeding season from August through May, males, juveniles, 

and some females of this species are abundant in the gulf. During that period, 10 to 40 percent of the total local population are females. The sea lions are seen locally on docks, on nearshore rocks, and in large numbers on the Farallon and Año Nuevo 

Islands, along the Point Reyes headlands, and at Bodega Rock. They feed on anchovy, 

herring, hake, mackerel, crabs, and squid. In times of low productivity, they have been 

known to feed on red pelagic crabs, sharks, eels, birds, and algae. 

Also common in the Gulf of the Farallones is the northern elephant seal, one of 

the deepest-diving marine mammals. Adult female elephant seals can dive to depths of 

4,000 feet and males to 5,700 feet. While at sea, these seals are submerged 80 to 90 percent of the time. Hunting, feeding, and sleeping all take place underwater. They 

come on land only to breed and molt. Their breeding season begins during December and ends in mid-March. Deep-water fish 

and invertebrates—squid, octopus, hagfish, ratfish, hake, and rockfish—are their primary foods. 

Other marine mammals observed in the 

gulf include four species Federally listed as endangered—fin whale, sei whale, right whale, and sperm whale. Two other species are listed as threatened—Guadalupe fur seal and southern sea otter. Many additional species of marine mammals have been observed in the gulf. Apart from the minke whale, which is a baleen whale, these species are all members of the group known as “toothed whales.” They include 

the northern right-whale dolphin, shortbeaked common dolphin, long-beaked common dolphin, bottlenose dolphin, striped dolphin, spotted dolphin, Risso’s dolphin, killer whale, short-finned pilot whale, pygmy sperm whale, dwarf sperm whale, Cuvier’s beaked whale, Baird’s beaked whale, Hubb’s beaked whale, and 

Blainville’s beaked whale. 

es in the Gulf of the Farallones 
Gray whale straining water from its mouth (photograph courtesy of Jim Cubbage). Gray whales are 

“baleen” whales—instead of teeth, they have numerous long overlapping strips of elastic fingernail-like material, called baleen (inset), hanging from their upper jaws that they use to filter out food (photograph from Gulf of the Farallones National Marine Sanctuary). “Whale watching” is a popular activity in the Gulf of the Farallones and helps to highlight the important ecological roles played by marine mammals. 

Marine Mammals 49 
Adult females and immature northern elephant seals at Southeast Farallon Island. Inset shows the characteristic nose of an adult male. (Photographs from Gulf of the Farallones National Marine Sanctuary.) 

es in the Gulf of the Farallones 
 Harbor seals resting on shore. (Photograph from Gulf of the Farallones National Marine Sanctuary.) 

Adult male and female Steller sea lions at a breeding colony. This species is Federally listed as threatened under the Endangered Species Act. (Photograph 

courtesy of Robert Wilson.) 

Immature California sea lions at play in 

the surf. (Photograph by Jan Roletto, Gulf of the Farallones National Marine Sanctuary.) 

Marine Mammals 51 
ches in the Gulf of the Farallones 

s 

rodon car

e Farallon 

a lions (pin

Mammals). 

underbelly 

ronment, 

ing pinni

t deal of 

be weeks or 

unities. 

 fall months, 

g (1- and 

als arriving 

 immature 

e white 

servations 

rks eat 

s more fre

peds, such 

or seals. 

ve at the Far

ginning in 

gh Novem

nd surge 

r undis

ng areas. 

ch are the 

e islands, 

h up on the 

 they are 

and surge 

channels. The fall haul out of elephant seals 

is commonly their first visit to the islands. Many of these seals are from other colonies, such as those at the Channel Islands or Point Año Nuevo to the south, and they may 

be unaware of white sharks patrolling the 

waters around the Farallon Islands. 

Studies of white sharks in the Gulf of 

the Farallones begun in 1987 have revealed the remarkable way in which these predators are able to locate and catch pinnipeds. Using photographs of dorsal and tail fins, and underwater videotapes of entire sharks, it has been possible to identify individual white sharks and follow their movements in the gulf over many years. Several of the larger sharks have been seen in the same areas for more than 5 years. When individual 

sharks are identified, they are always seen in 

the same area. However, some of the sharks are regular visitors, whereas others are only intermittently seen in the gulf. 

By 1995, monitoring of individual white 

sharks around the Farallon Islands, using small transmitters swallowed by the animals, had documented their movement patterns and internal temperatures. The movement 

patterns indicate that each shark has an area that it covers by zigzagging back and forth. These sharks are not swimming aimlessly; they increase their odds of finding pinnipeds 

by looking in familiar areas where they have previously been successful. The largest 

sharks covered the smallest home ranges and the smallest shark tracked covered the largest home range. The larger, older sharks 

seem to be more experienced and therefore know where to search. 

Monitoring found that white sharks in 

the Gulf of the Farallones maintain a constant body temperature of nearly 80°F in the cold (54 to 57°F) water of the gulf. This 

allows them to move quickly and to capture 

warm-blooded marine mammals, such as pinnipeds. Most of the world’s predatory sharks cannot increase their body temperature above the ambient water temperature, and so their range is limited to warmer tropical waters. 

High tides and large swells affect the 

rate of white shark predation on pinnipeds in the waters around the Farallon Islands. Such conditions force many of the seals to move from their haul-out space. This 

displacement may explain why significantly 

more attacks on elephant seals—sometimes two or three in one day—are observed when 

large swells are combined with high tides. 

Despite the white shark’s fearsome reputation and Hollywood image, attacks on 

humans are relatively rare. In northern and central California, there is on average one or 

two white shark attacks on humans per year and about one fatality per decade (chances of drowning in the State’s coastal waters are at least 100 times greater). In most of these instances, the shark has bitten only once and then released the person immediately. Those bitten usually survive if they can make it to shore, so swimming alone is not advised. Some evidence suggests that white sharks do not like the “taste” of people but sometimes 

mistake them for there favorite prey, pinnipeds. Therefore, it is not advisable to swim or surf near colonies of pinnipeds, where white sharks may be actively feeding. Areas where there has been a history of shark attacks should also be avoided. For these 

reasons, sport divers avoid the waters around the Farallon Islands. 

The population of white sharks off California’s coast is probably small, having 

perhaps a few hundred to a few thousand 

adults. White sharks are important predators in the State’s marine ecosystems. In 1994, with the support of scientists, fishermen, surfers, divers, and others, the State of California placed the white shark on the list of species protected in its waters. 

es in the Gulf of the Farallones 
White sharks do not swim aimlessly; 

they increase their odds of finding seals by looking in familiar areas where they have previously been successful. The map shows the movements of a white shark tracked during October 21–29, 1993, around Southeast Farallon Island, using a transmitter swallowed by the animal. 

The white shark is a fearsome predator, well adapted to live in cold water, 

where food is more abundant. It is far from a “primitive” cold-blooded fish but is actually a highly evolved warmblooded animal. 

Fisherman's Bay 

Mirounga Bay 

aintop 

y 

 OF A WHITE SHARK OVER 9 DAYS 

Southeast 

Farallon Island 

0 0 200 FEET 

100 200 METERS 

White Sharks 53

ally, staying near 

et deep (top) and 

er water (bottom). 

 and light under

nment, hiding the 

l prey. 

10:36 

0 0

30 60 90 

120 

0 

30 60 90 

120 150 

10 20 30 40 0 10 20 30 40 

50 

10:51 11:06 11:21 a.m.

11:57 � � � � � � � � � � � � � � � � � � � � � � � � � � � � 12:12 � � � � � � � � � � � � � � � � � � � � � � � � � � � �� � � � � �12:27� � � � � � � � � � � � � � � � � � � � �� � � � � � � 12:42 p.m.

Depth, in meters Depth, in meters 

Depth, in feet Depth, in feet 

Time Time 

SHALLOWER WATER DEEPER WATER 

WHITE SHARKS SEARCH FOR FOOD VISUALLY 

es in the Gulf of the Farallones 
 Gulls hover over a predatory attack by 

a white shark on a northern elephant seal. Southeast Farallon Island is in the background. 

Attack by white sharks is violent and quick; the sharks 

can strike quickly because they are warm blooded. 

White Sharks 55

ches in the Gulf of the Farallones 

Slope Communities


he Gulf of 

ns of the 

eased and 

 over the 

 stocks have 

been forced 

ets. 

in the gulf 

nental Shelf, 

area of the 

At a depth 

arts to drop 

ed the Con

d middle 

he new fish

hed. Because 

 waters are 

hallower 

harvesting, 

erm viabil

tinental 

rly freezing 

ght condi

Because 

 at these 

s—they eat 

gesting 

 more 

 ages than 

hallower 

waters—some deep-sea rockfish live more than 70 years. 

Many of the animals living in the perpetual darkness of the Continental Slope have 

developed light-producing organs. These serve various functions, such as communicating with members of their own kind (as in courtship), attracting food (like attracting moths to a flame), and avoiding being eaten (flashing a light in a predator’s eyes can 

give an animal a chance to get away). 

Another adaptation to the darkness is 

an absence of color diversity. With no 

light, colors have little function. Therefore, animals living on the Continental Slope are generally a dark color, like black, 

brown, or red. Among the fishes, rockfish 

and thornyheads are dominantly red. Red objects appear black at depth, allowing red 

organisms to blend in with their dark surroundings. 

The water pressure on the sea floor at the 

top of the Continental Slope is more than 10 times higher than at the surface, and at the bottom of the slope the pressure can be more than 100 times higher than at the surface. To compensate for this high pressure, organisms have a large percentage of 

water in their tissues, bones, and shells that replaces other substances, such as gases and calcium. Owing to the high water content of 

their tissues, many larger, older fish caught from deeper waters are limp and soft when brought to the surface. 

Fishes living at different depths on the 

Continental Slope have different life histories. Species living near the top of the slope produce pelagic (open-ocean) young that spend the first few months to years of life swimming in the upper water column and then settle out in relatively shallow water and migrate downslope as they grow and mature. Dover sole, sablefish, and rockfish have this type of life history; however, 

most species living deeper, such as rattails, 

deep-sea soles, and slickheads, have young that live in the same depths as the adults. 

Relatively few species occur at all or 

most depths on the Continental Slope. Species occupying one depth commonly are replaced by similar species at other depths. An exception is the eel-like hagfish, which is found at all depths on the slope. 

Productive commercial fisheries operating today on the Continental Slope off 

California’s coast catch Dover sole, sablefish, deep-living rockfishes, and thornyheads. Many of these fishes occupy similar 

habitats and generally are caught together. One increasingly active fishery is for rattails, a deep-living fish with a large head 

and a long tail that tapers to a point. 

One major fishery of note is for hagfish, 

the skin of which is used to make what are sold as “eel skin” wallets. Hagfish are not 

true eels but are a primitive group of fish that 

have no bones or jaws. Instead of bones, they have cartilage, and instead of jaws, they have 

a large sucker-like mouth similar to that of a lamprey or a leech. Once attached, hagfish use a tongue with many tiny teeth to dig into their prey. Once inside, the prey is eaten from 

the inside out. Besides its unique method of eating, the hagfish has another interesting trait—it produces copious amounts of slime, probably used to discourage predators, which gives the fish its nickname, the “slime eel.” 

Except for fishing activities, the Continental Slope and its communities of 

fish and invertebrates are still virtually untouched by humans, offering scientists the opportunity to study a generally undisturbed natural system. New methods, such as viewing animals and their habitat by underwater video cameras in submarines and in remotely operated vehicles, have 

been particularly productive in providing a new understanding of fish and invertebrates living on the slope. In the Gulf of the Farallones, scientists are using these methods to collect data at increasingly greater depths, providing critical information needed to better protect these areas from overuse. 

es in the Gulf of the Farallones 
Northern lampfish with light organs (small white 

circles) along its underside. This small fish, only about 2.5 inches long, also displays the dark coloration typical of many animals on deeper parts of the Continental Slope. (Photograph courtesy of K. Sakuma and D. Roberts.) 

Because of the absence of light on the Continental Slope, animals living there are generally either a dark color, such as the sablefish (left), or red, such as the shortspine thornyhead (right). 

Continental Slope Communities 57 
Juvenile rockfish swimming over Cordell Bank in the 

northern Gulf of the Farallones. Species of fish living near the top of the Continental Slope in the gulf produce pelagic (open-ocean) young that spend the first few months to years of life swimming in the upper water column and then settle out in relatively shallow water and migrate downslope as they grow and mature. (Photograph courtesy of Robert Schmieder, Cordell Expeditions.) A red-banded rockfish on the Continental Slope in the Gulf of the Farallones. Relatively few species of fish occur at all or most depths on the slope. Those occupying one depth commonly are replaced by similar species at other depths. For example, greenstriped and stripetail rockfishes live on muddy bottoms on the upper part of the slope, whereas at greater depth they are replaced by species of thornyheads. 

es in the Gulf of the Farallones 
Thornyheads, giant brittle stars, and other animals 

on the deeper Continental Slope in the Gulf of the Farallones. (Photograph from Gulf of the Farallones National Marine Sanctuary.) 

Continental Slope Communities 59 
s, when the California Gold Rush fi

rst brought frantic development 

o Bay region, the waters of the bay and of the Gulf of the Farallones, 

Gate, have been used to dispose of manmade waste. Perhaps of 

e thousands of barrels of low-level radioactive waste dumped in the 

decades following the Second 

World 

War. To evaluate the hazard 

o the marine environment, including increasingly important fisheries, 

n the search for containers of radioactive waste on the sea floor 

he need to find suitable places in the gulf to dump material dredged 

nels in San Francisco Bay. Studies of the sea floor in the gulf have 

 Environmental Protection Agency to designate the Nation’s fi

rst 

l site for dredge spoils. 

Management in the Gulf of the Farallones 

redged Material and Other Waste on the Continental Shelf and Slope


the Gulf 

d with the 

he San Fran

 Gold Rush 

ux of people 

n the bay 

inated sedi

he Sierra 

to San 

rried by 

e and into 

s inhabitants 

t flowed or 

ually, waste 

o the gulf. 

of waste has 

e Farallones. 

ed sediment 

ipping chan

d fruit can

on, surplus 

War II, other 

 low-level 

rs and inad

on of most 

ly known. 

mately 

adioactive 

f south and 

m 1958 to 

1969, the U.S. military disposed of chemical and conventional munitions at several sites in the gulf, mostly by scuttling 

World 

War II era 

cargo vessels. 

The hulks of ships, possibly dating as far 

back as the 17th century, litter the sea floor in 

the gulf. From 1951 to 1987, many vessels were deliberately sunk there. Most of these probably pose little environmental hazard because they were carefully prepared before sinking. One exception may be the highly radioactive World 

War II aircraft carrier USS 

Independence, exposed in atomic tests at Bikini Atoll in 1946 and sunk by the U.S. Navy in 1951 at an unspecified location off the California coast, possibly in the gulf. 

Since at least 1959, some sediment 

dredged from San Francisco Bay and from the sandbar outside the entrance to the bay (the Golden Gate Bar) has been dumped onto the Continental Shelf in the gulf. Much of this material is from dredging to maintain shipping channels into and within the bay, but some is from other engineering projects. 

Until 1970, ocean disposal of both radioactive and nonradioactive waste was acceptable under government policy. That year, the 

United States terminated all ocean disposal of radioactive waste materials. In 1972, Congress passed the Ocean Dumping Act, which 

regulates the dumping of wastes into ocean 

waters. A global ban on the dumping of radioactive waste in the oceans took effect in 1983. 

The Environmental Protection Agency 

(EPA) is currently responsible for designating ocean disposal sites for the United States. The U.S. Army Corps of Engineers 

(USACE), with EPA’s concurrence, issues permits for ocean disposal of dredged material at designated sites. Only sediments evaluated as “clean” (non-toxic) by EPA standards may be disposed of in the marine environment. 

San Francisco Bay’s 85 miles of navigable waterways require annual maintenance 

dredging. The bay’s average depth is about 19 feet, but oil tankers and container vessels need from 40 to 60 feet of water for safe transit. Environmental concerns and limited disposal capacity for dredged material in the bay have made it necessary to find suitable dumping sites in the ocean beyond the Golden Gate. 

A new approach for the management of 

dredging and disposal of dredged material for San Francisco Bay was coordinated under a regional effort begun in 1990 as a Federal-State partnership of four agencies and later joined by about 30 other public and private organizations. This effort was 

formally called the Long 

Term Management 

Strategy (LTMS) for the San Francisco Bay 

region. The primary task of the LTMS was 

to develop a long-range plan for meeting the bay region’s need to dispose of an estimated 300 million cubic yards of dredged material over the next 50 years. The EPA, a leading Federal agency in this effort, had the responsibility for selecting a location for an ocean disposal site for dredged material. 

In 1990, the U.S. Geological Survey 

(USGS) was asked by EPA, USACE, and the Navy to investigate four study areas for 

locating potential disposal sites for dredged material in the Gulf of the Farallones. This survey also tested the feasibility of using sidescan sonar to locate the radioactive-waste 

containers in the gulf (see chapter on Search for Containers of Radioactive Waste on the Sea Floor). 

Each of the four study areas was evaluated by the USGS for the presence of deposition and erosion, sediment transport pathways, and the likely effect deposited dredged 

material might have on the stability of the sea floor (see earlier chapters). 

Using the results of the USGS studies, 

EPA in 1994 designated the San Francisco Deep-Ocean Disposal Site. This site is 55 miles beyond the Golden Gate and 5 miles outside of the Gulf of the Farallones National Marine Sanctuary in 8,200 to 9,800 feet of water. 

nagement in the Gulf of the Farallones 
W 123° 122°30' 

Map of the Gulf of the Farallones, showing sites of historical waste disposal, as well as locations of U.S. Environmental Protection Agency (EPA) Study Areas (shaded) and Alternative Sites (dotted outlines). Study Areas 2 through 5 and Alternative Sites 3 through 5 were investigated by the U.S. Geological Survey (USGS) for possible designation by the EPA as disposal sites for dredged material. After the USGS reconnaissance survey, Study Areas 3, 4, and 5 on the Continental Slope were retained, and Study Areas 1 and 2 on the Continental Shelf were eliminated from further consideration. In 1994, the EPA designated Alternative Site 5 as the San Francisco Deep-Ocean 

Study Area 2 

Study Area 1 

Pt. Reyes 

Study Area 3 

Study 

Area 

4 

udy Area 5 

Alternative 

Site 3 

Alternative 

Site 4 

San 

Francisco Farallon 

Islands San 

Francisco 

Bay 

Half 

Moon 

Bay 

50m 

50 m 

00 m 500 m 200 m 

GUMDROP 

EAMOUNT 

CORDELL 

BANK 

UIDE 

MOUNT 

PIONEER 

CANYON 

SS Puerto Rican 

USS Independence? 

6 + 

5 + + 2 

+ 7 

+ 1 

4 + 

10 + 8 + 

+ 

11 

+

3A 

13 12 

9 

+ 

3B 

0 0 0 KILOMETERS 

20 NAUTICAL MILES 

BATHYMETRIC (DEPTH) CONTOURS IN METERS 

(1 METER = 3.281 FEET) 

2

Disposal Site. 

SITES OF HISTORICAL WASTE DISPOSAL 

 - 5 + Dredged material 8 - 10 + Low-level radioactive waste 

6 + Acid waste Farallon Islands Radioactive 7 + Cannery waste Waste Dump (FIRWD) 

11 - 13 Explosives and munitions 

Disposal of Dredged Material and other Waste on the Continental Shelf and Slope 63 
ged from the 

g channels has 

cularly in its 

and. These 

 the bay floor 

cts of dumping 

erial between 

tlined by the 

y the U.S. Geo

tric data and 

Grid squares 

e vertical exag

nagement in the Gulf of the Farallones 
The USS Independence during active service as a U.S. 

Navy aircraft carrier (left). The ship is shown below as it appeared after being exposed to atomic tests at Bikini Atoll in 1946. (U.S. Navy photographs.) 

Detail of a U.S. Geological Survey sidescan-sonar mosaic from an area of the upper Continental Slope about 20 miles southwest of the Farallon Islands. On this image was discovered what is interpreted to be the USS Independence (CVL 22), a dangerously radioactive aircraft carrier scuttled in 1951. Also visible is the stern section of the SS Puerto Rican, 

an oil tanker that sank in 1984. 

Disposal of Dredged Material and other Waste on the Continental Shelf and Slope 65 
Management in the Gulf of the Farallones 

ontainers of Radioactive Waste on the Sea Floor


ximately 

level radio

e Pacific 

These con

s, were to 

sites in 

many were 

 because 

ational 

ly litter a 

or, much 

the Far

ary, which 

 1981. 

ere the 

 to as 

ve Waste 

ribution 

as 

al environ

r contami

ble. Such 

ndividual 

ment and 

 and directly 

mersible was 

the 

aste Dump, 

drums were 

e drum was 

retrieved from this site by a manned submersible. However, use of submersibles in this type of operation is highly inefficient and very expensive without a reliable map to direct them. 

In 1990, the U.S. Geological Survey 

(USGS) and the Gulf of the Farallones National Marine Sanctuary began a cooperative survey of part of the waste dump using sidescan sonar—a technique that uses sound waves to create images of large areas of the ocean floor. Because of limited time and funding, the survey only covered about 80 square miles, or 15 percent of the waste dump area. 

Expert skills are required to distinguish 

waste drums and other manmade objects from natural geologic features or acoustic noise on ordinary sidescan-sonar images produced onboard ship. USGS scientists developed new techniques for enhancing the sidescan-sonar data from the Farallon Islands Radioactive Waste Dump to detect waste drums more easily and to distinguish them from other targets with a high level of confidence. Using these techniques, it was also possible to differentiate real targets (drums) from acoustic noise. 

The enhanced images from the survey 

showed the locations of many objects that the scientists interpreted to be radioactive 

waste containers. In 1994, the USGS, the Marine Sanctuary, and the U.S. Navy used the Navy’s DSV (Deep Submergence 

Vehicle) Sea Cliff and unmanned Advanced 

Tethered 

Vehicle (ATV) to verify these 

interpretations by direct observation of the sea bottom. The previous attempts in the mid-1970’s to locate waste drums in the Gulf of the Farallones using submersibles had been like trying to find a needle in a haystack and had little success. 

Using the enhanced sidescan-sonar 

images as guides, Sea Cliff and 

ATV were 

able to “drive” directly from one suspected drum site to the next. In every instance, waste containers and other physical features were found where the enhanced images showed them to be, and no containers were found where they were not indicated. 

This was the first successful test of 

locating barrels by regional mapping and, in that regard, represents a breakthrough. By using the new USGS maps to detect suspected barrel sites and U.S. Navy technology to directly view the sea floor, many barrels and other containers were found during just a single 24-hour 

ATV deployment, and each DSV Sea Cliff and 

ATV 

dive verified the predicted absence or presence of barrels. 

Visual observations 

revealed that the condition of the barrels 

ranged from completely intact to completely deteriorated. 

This work proved that enhanced sidescan-sonar images are a cost-effective and 

time-efficient method for locating relatively small objects on the sea floor and could be used to locate containers of hazardous waste in other ocean areas, such as Boston Harbor in Massachusetts and the Kara Sea in the Arctic Ocean north of Russia. 

Besides being the site of a marine sanctuary, the Gulf of the Farallones supports 

a major commercial fishery. In the past, fear of radiation contamination from leaking drums in the “Farallon Island Radioactive Waste Dump” has adversely affected 

the market for fish caught in the gulf. In 1998, the actual impact of the drums on the marine ecosystem began to be evaluated. Preliminary results suggest that it is much less than feared (see chapter on Measuring Radioactivity from 

Waste Drums on the 

Sea Floor). 

nagement in the Gulf of the Farallones 
CTIVE-WASTE DRUMS IN THE GULF OF THE FARALLONES


•

San Francisco 

Gulf of Farallones National Marine Sanctuary 

123°00' 122°30' 122°15'

NEER 

CANYON 

Farallon 

Islands 

0 20 KILOMETERS0 20 MILES 

N 

s National 

y 

ioactive Waste 

EXPLANATION 

Designated sites for dumping of 

radioactive waste used from 1946 

to 1970 

Area enlarged in image at upper right 

About 47,800 containers of low-level radioactive waste, mostly 55-gallon drums, were dumped in the Gulf of the Farallones from 1946 to 1970. These containers were to be dumped at the three designated sites (small stars) shown on the map at left. However, many containers were not dropped on target, probably because of inclement weather and navigational uncertainties, and lie scattered over an area of the sea floor commonly called the “Farallon Islands Radioactive Waste Dump.” An enlargement (above) of the area around one of the designated sites (large star) shows locations of probable radioactive-waste drums detected by the U.S. Geological Survey, superimposed on a sidescan-sonar mosaic. These images show 55-gallon drums thought to contain low-level radioactive waste on the 

Continental Slope in the Gulf of the Farallones. A corroded drum (top), with a large fish 

resting next to it, was photographed in the early 1990’s using a U.S. Geological Survey underwater-camera/video sled. An intact drum (bottom) was photographed in 1974 on a submersible dive sponsored by the Environmental Protection Agency. 

Search for Containers of Radioactive Waste on the Sea Floor 67

Management in the Gulf of the Farallones 

adioactivity from Waste Drums on the Sea Floor


and Johannes Limburg 

slands, off

 the San 

 of sea 

e “Farallon 

p.” This area 

0 large con

 of low-level 

between 

were to be 

, but they 

r of at least 

s ranging 

n 6,000 feet. 

d adjacent 

l fishery and 

t fishing and 

f radioactive 

ainers have in 

n the fishery. 

he drums 

d therefore 

 radiation or 

ible. 

Geological 

he Farallones 

yed part of 

nar—a tech

eate images 

see chapter 

oactive Waste 

echniques 

to enhance the sonar images, USGS scientists were able to identify many objects that they believed to be radioactive-waste containers. These identifications were confirmed in 1994 using U.S. Navy submersibles. 

In late 1994, discussions between the 

USGS and the British Geological Survey (BGS) led to a proposal to carry out a radioactivity survey of parts of the area where the 

drums had been mapped, using the BGS’s proven towed seabed gamma-ray spectrometer system. This system, called “EEL” 

because of its eel-like appearance, is towed 

along the sea floor and had to be modified to operate in the deeper waters found in the survey area. Previous attempts to measure radioactivity on the sea floor in the Farallon 

Islands Radioactive Waste Dump had been restricted to the analyses of samples of water, sediments, and marine animals and plants. Sediments from only a relatively small number of sites had been sampled, although in the mid-1970‘s some samples were collected from areas near drums found by chance using submersibles. 

Using drum locations indicated on the 

USGS sidescan-sonar images, a survey was designed to investigate regional-scale levels of radioactivity in the sea floor sediments of the gulf. In 1998, the BGS EEL was used to make continuous measurements of sea-floor 

radioactivity in the gulf along several tracklines. These were mostly at depths between 

300 and 3,000 feet, but some extended down 

to a maximum depth of about 4,900 feet. Samples of sea-floor sediment were collected on the basis of the EEL results and also were collected in areas where clusters of drums had been previously identified but where the seabed topography was too rugged for safe bottom towing of the EEL. 

Both measurements made by the EEL on 

the sea floor and laboratory analyses of sediment samples indicate only very low levels of artificial radionuclides (radioactive atoms, such as Cesium-137, that do not occur naturally but are produced by nuclear reactions) in the surveyed areas of the Farallon Islands Radioactive Waste Dump. These results are similar to those that had been reported in the limited previous studies. 

The results of the EEL survey suggest 

some leakage from drums in the Farallon Islands Radioactive Waste Dump, but it appears that this has caused only a localized increase in radionuclides on the sea floor in the gulf. The data do not suggest any 

significant elevation of radionuclide levels on a regional scale. Most of the observed variations in sea-floor radioactivity are due to changes in natural radioactivity and show a good correlation to geological features, and 

some of the very low levels of artificial radionuclides detected in the area surveyed may 

simply be from fallout from atmospheric nuclear testing done during the Cold 

War. 

It should be borne in mind that no data 

have yet been obtained for large areas of the Farallon Islands Radioactive Waste Dump. 

In particular, the deeper water areas where 

the majority of containers are believed to have been dumped remain virtually unstudied, both in terms of the radionuclide content of the sediments and the actual locations of the containers. 

To date, container locations have only 

been mapped in 15 percent of the Farallon Islands Radioactive Waste Dump and radionuclide concentrations examined in only about 10 percent of the dump area. Although the areas studied are the shallower parts of the site most accessible to people and where contamination would be of most concern, further studies must be done to fully evaluate the possible hazards from radioactivity in the Farallon Islands Radioactive Waste 

Dump. This could be important because, as many fish stocks have declined in the shallow coastal areas of the Gulf of the Farallones, some fishermen have been forced to 

fish in the deeper waters of the Continental Slope to fill their nets (see chapter on Continental Slope Communities). 

nagement in the Gulf of the Farallones 
 A seabed gamma-ray spectrometer belonging to and 

operated by the British Geological Survey, called the EEL because of its eel-like appearance, was used to measure the radioactivity of the sea floor in the Gulf of the Farallones. As shown in this diagram, the probe, housed in a protective hose (green), is towed along the sea floor. Data are sent up the towing cable to a shipboard computer and recorded continuously. The gamma-ray detector can measure both natural and artificial radioactivity in the top foot or so of sea-floor surface material. 

123°14' 

37°35' 37°36' 37°37' 37°38' 37°39' 

37°40'N 

123°13' 123°12' 123°11' 123°10' 123°09'W 

3.5 2.9 2.6 2.3 2.1 1.9 1.7 1.5 1.3 1.1 1.0 0.8 0.6 0.4 0.2 0.0 

-0.2 -0.6 -0.9 -1.7 

137Cs, in 

Becquerels per 

kilogram (Bq/kg) 

Sample site Waste drum Suspected drum Drum cluster 

0 0 KILOMETERS 

2 MILES 

N 

Distribution of measured cesium-137 (137Cs) radioactivity for the survey of the 900-meter dump (see area B on map, 

2

next page). This is an example of a plot produced from gamma-ray radioactivity data collected by the EEL in the Gulf of the Farallones. The EEL data from the gulf do not suggest any significant elevation of radionuclide levels on a regional scale. Most of the observed variations in sea-floor radioactivity are due to changes in natural radioactivity and show a good correlation to geological features but almost no correlation to the distribution of low-level radioactive-waste drums. Apparent negative radioactivity values are an artifact of data-processing calculations, combined with the statistical uncertainty inherent in measuring extremely low radioactivity levels. 

Measuring Radioactivity from Waste Drums on the Sea Floor 69 
arallones 


were measured 


. Also shown is 


slands Radio

ere approx­


 55-gallon 


were dumped 


s were to be 


mally referred 

0-meter sites), 


oor of at least 

ng from about 

nagement in the Gulf of the Farallones 
This photograph shows the British Geological Survey’s EEL being prepared for 

deployment in the Gulf of the Farallones. Housed within the green hose of the EEL are several instruments, including a gamma-ray detector that measures radioactivity on the sea floor. 

Measuring Radioactivity from Waste Drums on the Sea Floor 71 
al.html 

ea/eqmaps/ 

 1975, 

rn Califor

tain Press, 

rco, Bour

, Hendley, 

999, Sur

rom Chile, 

ological 

Helley, E.J., 

itional his

nges, and 

outhern San 

Geological 

014, 15 p. 

ochemical 

eological 

. 

, Stride, 

2, Sono

ture atlas: 

hing, 185 p. 

rface 

ng: Progress 

23–257. 

nd Geology, 

fornia, San 

o, California 

ogy, scale 

her, N.M., 

PA study 

Farallon 

seismic

H.A., ed., 

and geo

of the Far

ical Survey 

 Environ

. 55–103. 

Chin, J.L., Karl, H.A., and Maher, N.M., 

1997, Shallow subsurface geology of the continental shelf, Gulf of the Farallones, Calif., and its relationship to surficial seafloor characteristics: Marine Geology, p. 251–269. 

Chin, J.L., Rubin, D.M., Karl, H.A., 

Schwab, 

W.C., and 

Twichell, D.C., 

1989, Cruise report for the Gulf of the Farallones cruise F1–89–NC, F2–89–NC off the San Francisco Bay area: U.S. Geological Survey Open-File Report 89–417, 4 p. 

Collins, C.A., Garfield, N.R., Paquette, G., 

and Carter, E., 1996, Lagrangian measurements of subsurface pole

ward flow 

between 38°N and 43°N along the west coast of the United States during summer, 1993: Geophysical Research Letters, v. 23, no. 18, p. 2461–2464. 

Conomos, 

T.J., ed., 1979, San Francisco 

Bay, the urbanized estuary: San Francisco, American Association for the Advancement of Science, Pacific Division, 493 p. 

Dean, 

W.E., and Gardner, J.V., 1995, Geochemistry of surface sediments in the 

Gulf of the Farallones: U.S. Geological Survey Open-File Report 95–527, 57 p. 

Dymond, J., Suess, E., and Lyle, M., 1992, 

Barium in deep-sea sediment; a geochemical proxy for paleoproductivity: Paleoceanography, v. 7, p. 163–181. 

Gardner, J.V., Field, M.E., and 

Twichell, 

D.C. (eds.), 1996, Geology of the United States’ seafloor—the view from 

GLORIA: Cambridge, Cambridge University Press, 364 p. 

Engleman, E.E., Jackson, L.L., Norton, 

D.R., and Fischer, A.G., 1985, Determination of carbonate carbon in geological materials by coulometric titration: Chemical Geology, v. 53, p. 125–128. 

Hall, J.F., 1966, Fleishacker Zoo to Mussel 

Rock (Merced Formation)—a Plio-Pleistocene nature walk: California Division of Mines, Geological and Mineral Infomation Service, v. 19, p. S22–S25. 

Hickey, B.M., 1979, The California Current 

system—hypotheses and facts: Progress 

in Oceanography, v. 8, p. 191–279. 

Holland, H.D., 1979, Metals in black 

shales—a reassessment: Economic Geology, v. 74, p. 1676–1679. 

Ho

ward, A.D., 1979, Geologic history of 

middle California: Berkeley, University of California Press, 113 p. 

Huyer, A., Kosro, P.M., Fleischbein, J., 

Ramp, S.R., Stanton, 

T., Washburn, L., 

Chavez, F.P., Cowles, 

T.J., Pierce, S.D., 

and Smith, R.L., 1991, Currents and water masses of the coastal transition zone off northern California, June to August, 1988: Journal of Geophysical Research, v. 96, p. 14809–14832. 

Karl, H.A., ed., 1992, Comprehensive 

geological and geophysical survey of the gulf of the Farallones Region, central California: U.S. Geological Survey administrative report to U.S. Environmental Protection Agency, 188 p. 

Karl, H.A., Schwab, 

W.C., Drake, D.E., 

and Chin, J.L., 1992, Seafloor morphology and sidescan-sonar mosaics, in Karl, H.A., ed., Comprehensive geological and geophysical survey of the Gulf of the Farallones region: U.S. Geological Survey administrative report to U.S. Environmental Protection Agency, p. 30–54. 

Kious, 

W. J., and 

Tilling, R. I., 1996, This 

dynamic Earth—the story of plate tectonics: U. S. Geological Survey, 77 p. 

Klovan, J.E., and Miesch, A.T., 1976, 

Extended CABFAC and QMODEL computer programs for Q-mode factor analysis of compositional data: Computers and Geosciences, v. 1, p. 161–178. 

Largier, J.L., Magnell, B.A., and 

Winant, 

C.D., 1993, Subtidal circulation over the northern California shelf: Journal of Geophysical Research, v. 98, no. C10, p. 18147–18179. 

Lentz, S.J., ed., 1991, The coastal ocean 

dynamics experiment (CODE): Collected Reprints [see Journal of Geophysical Research, v. 92, no. C2, p. 1987]. 

Lentz, S.J., ed., 1995, U.S. contributions to 

the physical oceanography of continental shelves in the early 1990’s: Reviews of Geophysics, Supplement to v.33, p. 1225–1236. Maher, N.M., Karl, H.A., Chin, J.C., and Schwab, 

W.C., 1991, Station locations 

and grain-size analysis of surficial sediment samples collected on the continental shelf, Gulf of Farallones during 

cruise F2–89–NC, January 1989: U.S. Geological Survey Open-File Report 91–375–A, 42 p. 

McCulloch, D. S., 1985, Evaluating tsunami potential, in Ziony, J. I., ed., 

Evaluating earthquake hazards in the Los Angeles region: U. S. Geological Survey Professional Paper 1360, p. 375-413. 

McPhee, John, 1993, Assembling California: New 

York, Noonday Press, 304 p. 

Michael, A.J., Ross, S.L., Schwartz, D.P., 

Hendley, J.W., II, and Stauffer, P.H., 

1999, Major quake likely to strike between 2000 and 2030: U.S. Geological Survey Fact Sheet 152-99, 4 p. 

Miesch, A.T., 1981, Computer methods 

for geochemical and petrologic mixing problems, in Merriam, D.F., ed., Computer applications in the earth sciences: New 

York, Plenum, p. 244–265. 

Nichols, F.H., Cloern, J.E., Luoma, S.N. 

and Peterson, D.H., 1986, The modification of an estuary: Science, v. 231, p. 567–573. 

Noble, M., and Gelfenbaum, G., 1990, A 

pilot study of currents and suspended sediment in the Gulf of the Farallones: U.S. Geological Survey Open-File Report 90–476. 

Noble, M.A., and Kinoshita, K., 1992, Currents over the slope off San Francisco 

CA: U.S. Geological Survey Open-File Report 92-555. 

Noble, M.A., and Ramp, S.R., 2000, Subtidal current patterns over the central 

California—evidence for offshore veering of the undercurrent and for direct, wind-driven slope currents: Deep-Sea Research II, v. 47, p. 871-906. 

Noble, M., Ramp, S.R., and Kinoshita, 

K., 1992, Current patterns over the 
e Gulf of 

mary: U.S. 

Report 

K., 1996, 

ents in 

ed HF 

eophysi

–20686. 

endley, 

d a safer 

rieta earth

y Fact 

K.H., 

 Best, J.S., 

of cold 

alifornia, 

Geophysi

–14884. 

Garfield, 

furcated 

r; a cold 

y: Conti

no. 9, p. 

ndley, J.W., 

 Niño sea

fornia’s 

S. Geologi

4 p. 

esan, 

floor: U.S. 

079, 24 p. 

eology: 

17 p. 

er, A., 

filaments 

em: Jour

v. 96, p. 

, D.J., 

r, P.H., 

at quake 

. S. Geo

-96, 2 p. 

970, Geo

summary 

 65, p. 

Wahrhaftig, Clyde, 1984, A streetcar to 

subduction and other plate tectonic trips by public transport in San Francisco: Washington, D.C., American Geophysical Union, 76 p. 

Wallace, R.E., ed., 1990, The San Andreas 

fault system: U.S. Geological Survey Professional Paper 1515, 283 p. 

Ward, P.L., 1990, The next big earthquake 

in the Bay area may come sooner than you think: U.S. Geological Survey, 23 p. 

Washburn, L., Swenson, M.S., Largier, 

J.L., Kosro, P.M., and Ramp, S.R., 1993, Cross-shelf sediment transport by an anticyclonic eddy off northern California: Science, v. 261, p. 1560–1564. 

Wilde, P., Lee, J., Yancey, T., and Glogoczowski, M., 1973, Recent sediments of 

the central California continental shelf. Part C. Interpretation and summary of results: Berkeley, University of California, Hydraulic Engineering Laboratory Technical Report HEL 2–38, 83 p. 

Wong, F.L., and Klise, D.H., 1986, Heavy 

mineral, clay mineral, and geochemical data of surface sediments from coastal northern California rivers: U.S. Geological Survey Open-File Report 86–574, 13 p. 

Working Group on California Earthquake 

Probabilities, 1988, Probabilities of large earthquakes occurring on the San Andreas Fault: U. S. Geological Survey Open-File Report 88-398, 62 p. 

Working Group on California Earthquake 

Probabilities, 1990, Probabilities of large earthquakes in the San Francisco Bay Region, California: U. S. Geological Survey Circular 1053, 51 p. 

Working Group on Northern California 

Earthquake Potential, 1996, Database of potential sources for earthquakes larger than magnitude 6 in northern California, U.S. Geological Survey OpenFile Report 96-705, 53 p. 

Yancey, T.E., and Lee, J.W., 1972, Major 

heavy mineral assemblages and heavy mineral provinces of the central California coast region: Geological Society of America Bulletin, v. 83, p. 2099–2104. 

Biology http://www.prbo.org/ http://www-bml.ucdavis.edu/bmlresearch.html http://www.nps.gov/pore/ http://www.pfeg.noaa.gov/tib/index.htm http://sanctuaries.nos.noaa.gov/ Ainley, D.G., 1976, The occurrence of seabirds in the coastal region of California: 

Western Birds, v. 7, p. 33–68. 

Ainley, D.G., and Allen, S.G., 1992, Abundance and distribution of seabirds and 

marine mammals in the Gulf of the Farallones: Stinson Beach, Calif., Point Reyes Bird Observatory, Long-Term Management Strategy (LTMS) study group final report to U.S. Environmental Protection Agency (region 9), 300 p. 

Ainley, D.G., and Boekelheide, R.J., eds., 

1990, Seabirds of the Farallon Islands: Stanford, Calif., Stanford University Press, 450 p. 

Ainley, D.G., Sydeman, W.J., Hatch, S.A., 

and Wilson, U.W., 1994, Seabird population trends along the west coast of North America; causes and the extent of regional concordance: Studies in Avian Biology, v. 15, p. 119–133. 

Allen, S.G., 1994, The distribution and 

abundance of marine birds and mammals in the Gulf of the Farallones and adjacent waters, 1985–1992: Berkeley, University 

of California, Ph.D. thesis, 300 p. 

Allen, S.G., and Huber, H.R., 1987, Pinniped 

assessment in Point Reyes, California, 

1983 to 1984; final report to Point Reyes/ Farallon Islands National Marine Sanctuary: San Francisco, U.S. National Oceanic and Atmospheric Administration Technical Memorandum NOS MEMD 7, 71 p. 

Allen, S.G., Ainley, D.G., Fancher, L., and 

Shuford, D., 1987, Movement and activity patterns of harbor seals (Phoca vitulina) from Drakes Estero population, California, 1985–86; final report to Point Reyes/Farallon Islands National Marine Sanctuary: San Francisco, U.S. National Oceanic and Atmospheric Administration Technical Memorandum NOS MEMD 6, 36 p. 

Alton, M.S., and Blackburn, C.J., 1972, 

Diel changes in the vertical distribution of the euphausiids, Thysanoessa spinifera Holmes and Euphausia pacifica 

Hansen, in coastal waters of Washington: California Fish and Game, v. 58, 

no.3, p. 179–190. 

Anderson, D.M., 1994, Red tides: Scientific 

American, August, p. 62–68. 

Barlow, J., 1993, The abundance of cetaceans in California waters estimated 

from ship surveys in summer/fall 1991: 

U.S. National Oceanic and Atmospheric Administration, National Marine Fisheries Service/Southwest Fisheries Science Center Administrative Report LJ–93–09, 39 p. 

Bonnell, M.L., Pierson, M.O., and Farrens, 

G.D., 1983, Pinnipeds and sea otters of central and northern California 1980–83; status, abundance, and distribution: Santa Cruz, University of California, Minerals Management Service Contract Report 14–12–0001–29090. 

Botsford, L.W., Quinn, J.F., Wing, S.R., 

and Brittnacher, J.G., 1993, Spatial management of a benthic invertebrate, the red sea urchin Strongylocentrotus franciscanus: Proceedings of the International Symposium on Management Strategies for Exploited Fish Populations, Alaska Sea Grant College Program Report 93-02. 

Botsford, L.W., Wing, S.R., and Largier, J.L., 

1998, Population dynamic implications of larval dispersal in meroplanktonic populations, in Pillar, S.C., Moloney, C.L., Payne, 

A.I.L., and Shillington, F.A., eds., Benguela dynamics—Impacts of variability on shelf-sea environments and their living resources: South African Journal of 

Marine Science, v. 19. 

Boyd, I.L., ed., 1993, Marine mammals; 

advances in behavioral and population biology (Zoological Society of London Symposia, no. 66): New York, Oxford University Press, 426 p. 

Boydstun, L.B., Hallock, R.J., and Mills, 

T.J., 1992, Salmon, in Leet, W.L.,. 

Dewees, C.M., and Haugen, C.H., eds., 

Further Reading 73 
sources and 

University 

lication 

 

is, D.B., 

ird commu

1975–1983: 

 15, p. 

C., Steiger, 

Bloedel, P., 

of hump

the Far

to Inter

ion, special 

dbook 

e: Boca 

ber Co. 

man, M.L., 

aceans 

ifornia, 

e, and 

niversity 

nagement 

4–12– 

W., and 

d guide to 

n, Houghton 

 1968, Deep

erkeley, Uni

55 p. 

populations 

ast of Cali

lif., U.S. 

ospheric 

Marine Fish

heries 

script 

avo, I., 

A., and 

nce of 

oflagellates 

 de 

Vigo, 

nd Shelf 

Franks, P.J.S., 1992, Phytoplankton 

blooms at fronts; patterns, scales, and physical forcing mechanisms: Review 

of Aquatic Science, v. 6, no. 2, p. 121–137. 

Gage, J.D., and 

Tyler, P.A., 1991, Deepsea biology; a natural history of organisms at the deep-sea floor: New 

York, 

Cambridge University Press, 504 p. 

Gaskin, D., 1985, Ecology of whales and 

dolphins: Portsmouth, N.H., Heinemann Educational Books, Inc., 434 p. 

Haley, D., 1986, Marine mammals of eastern North Pacific and Arctic waters: 

Seattle, Wash., 

Pacific Search Press, 

312 p. 

Hallegraeff, G.M., 1993, A review of 

harmful algal blooms and their apparent global increase: Phycologia, v. 32, no. 2, p. 79–99. 

Hallegraeff, G.M., Anderson, D.M., and 

Cembella, A.D., eds., 1995, Manual on harmful marine microalgae: UNESCO, International Oceanographic Commission Manuals and Guides, no. 33, 550 p. 

Hamner, W.M., Hamner, P.P., Strand, S.W. 

and Gilmer, R.W., 1983, Behavior of Antarctic krill, Euphausia superba; chemoreception, feeding, schooling, and molting: Science, v. 220, no. 22, p. 433–435. 

Hanan, D.A., Jones, M.L., and Beeson, 

M.J., 1993, Harbor seal census in California, May–June, 1992: Final report to U.S. National Oceanic and Atmospheric Administration, National Marine Fisheries Service/Southwest Fisheries Science Center. 

Hart, J.L., 1973, Pacific fishes of Canada: 

Fisheries Research Board of Canada Bulletin 180, 740 p. 

Healy, M..C., 1991, Life history of chinook salmon (Oncorhynchus tshawytscha), in Croot, C. and Margolis, 

L., eds., Pacific salmon life histories: Vancouver, British Columbia, Canada, University of British Columbia Press, p. 311–394. 

Heyning, J.E., and Perrin, 

W.F., 1994, Evidence for two species of common dolphins (genus Delphinus) from the east- ern North Pacific: Los Angeles, Calif., Los Angeles County Natural History Museum Contributions in Science, no. 442, 35 p. Jones, M.L., Swartz, S.L., and Leatherwood, S., eds., 1984, The gray whale, Eschrichtius robustus: San Diego, Calif., Academic Press, 600 p. Jones, P.A., and Szczepaniak, I.D., 1992, Report on seabird and marine mammal censuses conducted for the Long-Term Management Strategy (LTMS), August 1990 through November 1991: San Francisco, Calif., report to U.S. Envi­ ronmental Protection Agency (region 9). Jones, R.E, 1981, Food habits of smaller marine mammals from Northern Cali­ fornia: California Academy of Sciences Proceedings, v. 42, no. 16, p. 409–433. Kieckhefer, T.R., 1992, Feeding ecology of humpback whales in continental shelf waters near Cordell Bank, Cali­ fornia: San Jose, Calif., San Jose State University, M.S. thesis, 86 p. Kieckhefer, T.R., 1996, Euphausiids fill critical food niche: Upwellings, News- letter of the Pacific Cetacean Group, UC–MBEST Center, Marina, Calif., 1996 upwelling season issue, p. 2–3. King, J.E., 1983, Seals of the world: Ithaca, N.Y., Cornell University Press. Klimley, A.P., and Ainley, D.G., eds., 1996, Great white sharks: New 

York, 

Academic Press, 517 p. 

Leatherwood, S., and Reeves, R.R., 1983, 

The Sierra Club handbook of whales and dolphins: San Francisco, Sierra Club Handbooks. 

Leatherwood, S., Reeves, R.R., Perrin, 

W.F., 

and Evans, 

W.E., 1988, Whales, dolphins and porpoises of the eastern North 

Pacific and adjacent Arctic waters; a guide to their identification: Mineola, N.Y., Dover Publications, 256 p. 

LeBoeuf, B.J., and Kaza, S., 1981, Natural 

history of Año Nuevo: Pacific Grove, Calif., Boxwood Press. 

LeBoeuf, B.J., and Laws, R., eds., 1994, 

Elephant seals; population ecology, 

behavior and physiology: Berkeley, 

University of California Press, 414 p. 

LeBoeuf, B.J., Ono, K., and Reiter, 

J., 1991, History of the Steller sea lion population at Año Nuevo Island, 

1961–1991: La Jolla, Calif., U.S. National Oceanic and Atmospheric Administration, National Marine Fisheries Service/Southwest Fisheries Service Center Administrative Report 

LJ–91–45C, 9 p. 

Lowry, M.S., Oliver, C.W., and Macky, C., 

1990, Food habits of California sea lion, Zalophus californianus, at San Clemente Island, California, 1981–86: Fisheries Bulletin, v. 88, p. 509–521. 

Mauchline, J., 1980, The biology of 

mysids and euphausiids: Advances in 

Marine Biology, no. 18, p. 1–680. 

Morgan, L.E., 

Wing, S.R., Botsford, L.W., 

Lundquist, C.J., and Diehl, J.M., 2000, Spatial variability in red sea urchin (Strongylocentrotus franciscanus) cohort strength relative to alongshore upwelling variability in northern California: Fisheries Oceanography, v. 9, p. 83-98. 

Orr, R.T., Helm, R., and Schoenwald, 

J., 1989, Marine mammals of California: Berkeley, University of California 

Press, 92 p. 

Oua, H.E., and Oua, B.L., eds., 1979, 

Behavior of marine animals: New 

York, 

Plenum Press, v. 3. 

Price, D.W., Kizer, K.W., and Hansgen, 

K.H., 1991, California’s paralytic shellfish poisoning prevention program, 1927–89: Journal of Shellfish 

Research, v. 10, no. 1, p. 119–145. 

Pyle, P., and Gilbert, L.,1996, Occurrence 

patterns and trends of cetaceans recorded from Southeast Farallon Island, California, 1973–1994: Northwest Naturalist, v. 77, p. 1–8. 

Pyle, P., and DeSante, D.F., 1994, 

Trends 

in waterbirds and raptors at Southeast Farallon Island, California, 1974–1993: Bird Populations, v. 2, p. 33–43. 

Quinn, J.F., Wing, S.R., and Botsford, 

L.W., 1993, Harvest refugia in marine invertebrate fisheries—Models and 
hin, Stron

merican 

Leather

ub hand

an Fran

. 

of pin

and Hall. 

 eds., 

e mam

ress, 5 v. 

ds; seals, 

ley, Uni

89, Meso

iid sound 

ental shelf 

n Journal 

nces, v. 46, 

opulation 

os Ange

 Service, 

021. 

88, Day

noessa 

e Gulf of 

letin of 

p. 76–84. 

f the 

ach, Calif., 

, 214 p. 

alaenop

erey Bay 

 Francisco 

9 p. 

., 1991, 

nses 

York, 

A., 1988, 

a otters: 

65 p. 

ier, J.L., 

spatial 

and crab 

ifornia 

ology 

9-211. 

Wing, S.R., Botsford, L.W., and Quinn, 

J.F., 1998, The impact of coastal circulation on the spatial distribution of invertebrate recruitment, with implications for management, in Jamieson, G.S., and Campbell, A., eds., Proceedings of the North Pacific Symposium on Invertebrate Stock Assessment and Management: Canadian Special Publication of Fisheries and Aquatic Sciences, v. 125, p. 285-294. 

Wing, S.R., Botsford, L.W., Ralston, S.V., 

and Largier, J.L., 1998, Meroplanktonic distribution and circulation in a coastal retention zone of the northern California upwelling system: Limnology and Oceanography, v. 43, no. 7, p. 1710-1721. 

Wing, S.R., Largier, J.L., and Botsford, 

L.W., 1998, Coastal retention and onshore transport of meroplankton near capes in eastern boundary currents, with examples from the California Current, in Pillar, S.C., Moloney, C.L., Payne, A.I.L., and Shillington, F.A., eds., Benguela dynamics—Impacts of variability on shelf-sea environments and their living resources: South African Journal of Marine Science, v. 19, p. 119-127. 

Wing, S.R., Largier, J.L., Botsford, L.W., and 

Quinn, J.F., 1995, Settlement and transport of benthic invertebrates in an intermittent upwelling region: Limnology and Oceanography, v. 40, p. 316-329. 

Environmental Issues http://www.spn.usace.army.mil/ http://www.epa.gov/region9/water/ 

dredging/sfdods/ 

Booth, J.S., Winters, W.J., Poppe, L.J., 

Neiheisel, J., and Dyer, R.S., 1989, Geotechnical, geological, and selected radionuclide retention characteristics of the radioactive-waste disposal site near the Farallon Islands: Marine Geotechnology, v. 8, p. 111-132. 

Chavez, P.S., Jr., and Karl, H.A., 1995, 

Detection of barrels on the seafloor using spatial variability analysis on 

sidescan sonar and bathymetry images: Journal of Marine Geodesy, v. 18, p. 

197–211. 

Colombo, P., and Kendig, M.W., 1990, 

Analysis and evaluation of a radioactive waste package retrieved from 

the Farallon Islands 900-meter disposal site: Environmental Protection Agency 

Report 520/1–90–014, 65 p. 

Dyer, R.S., 1976, Environmental surveys 

of two deep-sea radioactive waste disposal sites using submersibles, in International Symposium on the Management of Radioactive Wastes from 

the Nuclear Fuel Cycle, Vienna, Austria, 1976, Proceedings: International 

Atomic Energy Agency Report IAEA– Su/65, p. 317-338. 

Food Standards Agency/Scottish Environmental Protection Agency, 2000, 

Radioactivity in food and the environment, 1999 (RIFE-5): Scotland, Food Standards Agency/Scottish Environmental Protection Agency. 

Griggs, G.B., and Hein, J.R., 1980, 

Sources, dispersal, and clay mineral composition of fine-grained sediment off central and northern California: Journal of Geology, v. 88, p. 541-566. 

Jones, D.G., 1994, Towed sea-bed gamma 

ray spectrometer ‘Eel’ is radiometric instrument for wide range of offshore mineral exploration, environmental 

survey applications: Sea Technology, 

August 1994, p. 89-93. 

Jones, D.G., Miller, J.M., and Roberts, 

P.D., 1988, A seabed radiometric survey of Haig Fras, S. Celtic Sea, UK: Proceedings of the Geologists Association, v. 99, p. 193-203. 

Jones, D.G., Roberts, P.D., and Miller, 

J.M, 1988, The distribution of gammaemitting radionuclides in surface sediments near the Sellafield Plant: Estuarine Coastal and Shelf Science, v. 27, 

p. 143-161. 

Jones, D.G., Roberts, P.D., Limburg, J., 

Karl, H., Chin, J.L., Shanks, W.C., Hall, R., and Howard, D., 2001, Measurement of seafloor radioactivity at 

the Farallon Islands Radioactive Waste 

Dump Site, California: U.S. Geological Survey Open-File Report 01-062, 23 p. 

Jones, D.G., Roberts, P.D., Strutt, M.H., 

Higgo, J.J., and Davis, J.R., 1999, Distribution of Cs-137 and inventories 

of Pu-238, Pu-239/240, Am-241 and Cs-137 in Irish Sea intertidal sediments: Journal of Environmental Radioactivity, v. 44, p. 159-189. 

Joseph, A.B., Gustafson, P.F., Russell, 

I.R., Schuert, E.A., Volchok, H.L., and Tamplin, A., 1971, Sources of radioactivity and their characteristics, in Radioactivity in the marine environment: Washington, D.C., National 

Academy of Sciences, p. 6-41. 

Karl, H.A., ed., 1992, Comprehensive geological and geophysical survey of the 

Gulf of the Farallones region, central California: administrative report to U.S. Environmental Protection Agency, 146 p. 

Karl, H.A., Drake, D.E., and Schwab, 

W.C., 1992, Cruise narrative, chap. 1 

in Karl, H.A., ed., Comprehensive geological and geophysical survey of the Gulf of the Farallones region, central California: U.S. Geological Survey 

administrative report, p. 9–21. 

Karl, H.A., Schwab, W.C., Wright, A. 

St.C., Drake, D.E., Chin, J.L., Danforth, W.W., and Ueber, E., 1994, Acoustic mapping as an environmental management tool, I. Detection of barrels of low-level radioactive waste, Gulf of the Farallones National Marine Sanctuary, 

California: Ocean and Coastal Management, v. 22, p. 201-227. 

Kershaw, P.J., Denoon, D.C., and Woodhead, D.S., 1999, Observations on the 

redistribution of plutonium and americium in the Irish Sea sediments, 1978 to 1996—concentrations and inventories: Journal of Environmental Radioactivity, v. 44, p. 191-221. 

Miller, J.M., Roberts, P.D., Symons, G.D., 

Merrill, N.H., and Wormald, M.R., 1977, A towed sea-bed gamma-ray spectrometer for continental shelf surveys, in Nuclear Techniques and MinFurther Reading 75 
stria, Inter

ency, p. 

oberts, 

82, Mea

clide dis

bed spec

Bulletin, v. 

heric 

llon Islands 

ational 

Adminis

 Resource 

kela, T.A., 

, 1978, 

e envi

slands: 

atory, Uni

t No. 

, 1961, 

 disposal 

a, Pneumo

vanced Sys

n, Technical 

s, P.D., and 

ore geo

uding use 

meter for 

Bay, N.W. 

British 

al Report 

80, Radio

tive waste 

on Islands: 

5-496. 

sposal 

3, no. 2 

Suchanek, T.H., Lagunas Solar, M.C., 

Raabe, O.G., Helm, R.C., Gielow, F., 

Peek, N., and Carvacho, O., 1996, Radionuclides in fishes and mussels from the Farallon Islands nuclear waste 

dump site, California: Health Physics, v. 71, p. 167-178. 

Tetra Tech, Inc., 1992, Baseline ecological 

assessment of disposal activities in the Gulf of the Farallones; information identification, evaluation, and analysis: 

Pasadena, Calif., Tetra Tech, Inc., 44 p. 

U.S. Environmental Protection Agency, 

1993, Environmental impact statement (EIS) for designation of a deep water ocean dredge material disposal site off San Francisco, California: U.S. Environmental Protection Agency, 625 p. 

U.S. Environmental Protection Agency, 

Region 9, and U.S. Army Corps of Engineers, San Francisco District, San Francisco Bay Conservation and Development Commission, 1996, Long-term management strategy (LTMS) for the placement of dredged material in the San Francisco Bay region: U.S. Environmental Protection Agency, 2 v. 

Waldichuk, M., 1960, Containment of 

radioactive waste for sea disposal and fisheries off the Canadian Pacific coast, in Proceedings of International Atomic Energy Agency Symposium on Disposal of Radioactive Wastes: 

Vienna, Austria, International Atomic Energy Agency, v. 2. 
evice 

 current 

from the 

e sea 

 package 

rgy 

es signals 

d layers of 

sea floor, 

eflected 

 horizon

 an ocean 

n of the 

ally thin 

or both 

common 

associated 

and adja

r example, 

he deep 

 Earth’s 

sphere, 

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usive igne

a map 

a level on 

of ocean 

 topogra

disturbed 

with a 

 of certain 

ssures in 

 the sea 

kes a 

d (micro

composed 

of silica (SiO2), often from the tiny skeletons of aquatic microorganisms. 

Continental margin. The ocean floor that 

is between the shoreline and the deep (abyssal) ocean floor. 

Continental shelf. That part of the continental margin from the shoreline to the 

continental slope or, where there is no noticeable break in slope, to a depth of about 660 feet (200 meters). 

Continental slope. That part of the continental margin that is between the continental shelf and the deep (abyssal) 

ocean floor. 

Convergent boundary [currents]. An area 

or zone where ocean currents come together. 

Convergent boundary [plate tectonics]. 

A boundary between two tectonic plates that are moving to

ward each other. 

Coring device. An apparatus used to take 

vertical, cylindrical or rectangular sections of sediment from the sea floor. 

Core sample. A vertical, cylindrical or 

rectangular sample of sediment from which the nature or stratification of the sea-floor deposits may be determined. 

Crust [Earth’s]. The outermost layer or 

shell of the Earth. 

Current meter. A device that measures the 

speed and direction of ocean currents. 

Deep submergence vehicle. A submarine 

that is capable of submerging to very great depths, usually used for research. 

Diabase. An dark intrusive igneous rock. Diatom. A microscopic single-celled plant 

that secretes a silica (SiO2) skeleton; 

diatoms are abundant in both marine and fresh water. 

Dike. A tabular igneous intrusion that cuts 

across the bedding or foliation of the host rock. 

Dinoflagellate. A single-celled microscopic organism with resemblances to 

both plants and animals; most species are marine, and some are the cause of toxic “red tides.” 

Divergent boundary [currents]. The area 

or zone where different currents or 

water bodies move apart from each other. 

Divergent boundary [plate tectonics]. A 

boundary between two plates that are moving apart from each other. 

Eclogite. A granular rock composed essentially of garnet and sodic pyroxene. 

Ekman transport. The current generated 

from wind blowing over the surface of the water, where the surface current moves at 45 degrees to the right of the wind direction (northern hemisphere) and successively deeper layers of water 

move increasingly to the right until at some depth the water is moving opposite the wind direction; the net transport is 90 degrees to the right of the wind direction. 

El Niño. An anomalous warming of the 

surface waters of the eastern tropical Pacific Ocean, which can have worldwide and significant effects on weather, ocean currents, and sea life and can cause droughts, floods, and other natural disasters. 

Entrenched valley. A deepened, incised 

valley that suggests rapid vertical uplift or lowering of base level. 

Epicenter. The point on the Earth’s surface 

that is directly above the focus of an earthquake. 

Euphausiid. A group of small planktonic 

marine shrimp, commonly called krill, that are an important food source for many marine animals, including some whales. 

Eustatic [sea level]. Said of worldwide 

changes in sea level that affect all the world’s oceans. 

Exotic terrane. A geologic terrane that has 

moved far from its place of origin and is unrelated to those adjacent to it. 

Factor analysis. A mathematical technique 

used to discover simple patterns in relations among variables. 

Farallon Escarpment. The steep submarine slope in the region of the Farallon 

Islands; part of the Continental Slope. 

Farallon Shelf. The gently sloping part of 

the sea floor in the vicinity of the Farallon Islands from the shore to the Faral­ lon Escarpment; part of the Continental Shelf. Fault. A fracture or zone of fractures in the Earth along which there has been displacement of the sides relative to one another. Flagellates. Microorganisms possessing whip-like flagella, which they use for propulsion. Franciscan Complex/Assemblage. A dis­ orderly assemblage of rocks of various characteristics in the Coast Ranges of California that have undergone unsys­ tematic disturbance; typical rocks of this assemblage crop out in the vicinity of San Francisco. Franciscan mélange. A variation of Fran­ ciscan Assemblage; a mélange is char­ acterized by fragments and blocks of various rock types of all sizes. Gabbro. A dark, granular intrusive rock; the intrusive equivalent of basalt. Geomorphological. Pertaining to the gen­ eral configuration of the Earth’s surface; the nature and origin of landforms. Geophysics. The study of the Earth by quantitative physical means. Glacier. A large mass of ice formed by the accumulation, compaction, and recrys­ tallization of sno

w. 

Global Positioning System (GPS). A network of satellites used for navigation. 

Granite. A light-colored plutonic rock rich 

in quartz and feldspar. 

Granitic. Of or pertaining to granite. Gravity corer. A device with a long cylindrical pipe topped by a heavy weight 

used to take samples of sea-floor sediments. 

Graywacke. A dark-gray, hard, coarsegrained sandstone that consists of 

poorly sorted, angular to subangular mineral grains embedded in a clay matrix. 

Great Valley of California. Also called 

the Central 

Valley, it is a nearly flat alluvial plain in the central part of California about 450 miles long and on average 

50 miles wide. Geologically, the Great 

Glossary 77 
orthwest

led with a 

 that range 

ent. 

rals that 

er than a 

 to the high

 any period 

acial activ

ocene, which 

rs ago and 

ars ago. 

rals that 

rtly molten 

ice on a 

matically 

etermined 

placement 

ck, leading 

 rocks in 

and batho

(extruded) 

lso, the rock 

terial. 

ck com

arbonate 

hells of 

ortion of the 

nd upper

enosphere. 

er of rock 

logic char

position. 

igation 

to the 

ring any 

e Earth’s 

the strength 

hquake. 

 the Earth 

he core. 

Megalopa (megalops). An advanced larval 

stage of crabs, just preceding the adult stage. 

Mesozoic. An era of geologic time from 

about 225 to about 65 million years ago, best known as the time of the dinosaurs. 

Metamorphic. Pertaining to rocks and 

minerals that have been changed by heat and pressure. 

Oceanic plate. A tectonic plate of the 

Earth’s lithosphere that is characterized by thin basaltic crust; moves horizontally and adjoins other plates along seismically active zones. 

Pelagic. Said of marine organisms whose 

environment is the open ocean, rather than the bottom or shore areas. 

Photic (euphotic) zone. The upper zone 

of ocean waters in which sunlight penetrates sufficiently to support photosynthesis; generally the upper 150 to 450 feet of the water column. 

Photosynthesis. The process by which 

plants make organic compounds from carbon dioxide and water using the energy of sunlight, a byproduct of which is the production of free oxygen; photosynthesis is the primary basis for food production on Earth. 

Phytoplankton. Aquatic plants, mostly microscopic, that have a planktonic lifestyle. Pillow basalt. A type of basalt that is characterized by pillow-shaped structures, 

generally interpreted to indicate that it was erupted under water. 

Plankton. Aquatic plants and animals, 

chiefly microscopic, that drift or float in the water and are the main basis of marine food webs. 

Plate tectonics. A theory of global tectonics in which the lithosphere is divided 

into a series of plates that move horizontally relative to one another. 

Primary producers. Green plants, including most phytoplankton; so called 

because they produce, through photosynthesis, the organic compounds that form the beginning link in food webs. 

Radiolarian chert. A layered (well 

bedded) microcrystalline rock consisting of the remains of one-celled marine animals called radiolarians. Ranging navigation system [Del Norte/ Benthos]. A system used relatively close to shore to determine a precise position at sea. Red tide. A reddish discoloration of sea

water caused by a bloom of toxic dinoflagellates. 

Salinian terrane/block (Salinia). A 

300-mile-long slice of rock that forms most of the basement in the central coastal part of California, west of the San Andreas Fault; this terrane has been interpreted to be displaced northward from a southward extension of the Sierra Nevada or possibly from even farther south. 

Sea-floor spreading. The process in which 

new ocean crust is created by upwelling of magma at midoceanic-ridge spreading centers; as new crust is created, it moves horizontally a

way from the 

ridge. 

Seismic-reflection profile. A profile produced from the return of acoustic 

energy reflected off the sea floor and off density discontinuities at layers below the sea floor. 

Seismometer. An instrument that detects 

Earth motions. 

Serpentine. A group of common minerals, 

commonly a mottled shade of green, that form by alteration of olivine and other magnesium-rich minerals found in igneous and metamorphic rocks. 

Serpentinite. A characteristically green 

rock consisting almost wholly of serpentine-group minerals; it is a common rock type in coastal central California. 

Shelf break. An abrupt change in slope 

that marks the boundary between the Continental Shelf and Slope. 

Sidescan sonar. An acoustic device that 

emits sound signals to the side of a ship’s track; these signals are reflected back from the sea floor, revealing its character. 

Souter Van Veen grab sampler/corer. A 

jawed or clam-like device that grabs or 

scoops up samples of sediment from the sea floor. 

Stream valley. An elongate depression in 

the Earth’s surface carved by a stream. 

Structural fold. A fold in rock or strata 

produced by deformation. 

Subaerial. Processes or conditions, such as 

erosion, that exist or operate in the open air at the Earth’s surface. 

Subduction. The process of one lithospheric plate descending beneath 

another along a convergent boundary. 

Subduction zone. A zone along which subduction occurs. Tectonic plate. One of the large plates of 

lithosphere constituting the surface of the Earth that move horizontally relative 

to one another. 

Terrane. A fault-bounded body of rock of 

regional extent, characterized by a geologic history different from that of adjacent terranes. 

Terrestrial lowland. An area or place 

of low-lying land, especially near the coast. 

Towfish. A device towed on a cable behind 

a ship; commonly applied to a sidescansonar transceiver. 

Transform boundary. In plate tectonics, a 

plate boundary that ideally shows pure strike-slip displacement (two plates sliding horizontally past each other). 

Transmissometer. A device that measures 

levels of light in the water, providing an estimate of the amount of suspended particulate matter. 

Tsunami. A gravitational sea

wave initiated 

by a short-duration, large-scale disturbance of the sea floor, usually by strong 

earthquake. 

Unconformity. A substantial break or gap 

in the geologic record where a rock unit is overlain by another that is not next in 

stratigraphic succession. 

Water column. A vertical section of water 

from the surface to the bottom of a body of water. 

Zooplankton. Aquatic animals, mostly 

microscopic, that have a planktonic lifestyle. 
Oceanography and Geology of the Gulf of the Farallones 

The San Francisco Bay region of California is famous for its stunning landscapes and complex geology. Adjacent to this region, in the 

watery world of the Pacific Ocean beyond the Golden Gate, lies the Gulf of the Farallones, a physical environment equally complex and 

fascinating, but less obvious, less visible, and therefore more mysterious. 

Scientific studies are revealing that the sea floor of the gulf, like the region onshore, was crafted by geologic forces that include movements 

of the San Andreas Fault system, major changes in sea level, and the action of rivers. The ceaseless work of oceanic currents has further 

sculpted the sea bottom in the gulf into landscapes that today range from flat plains and giant sand ripples to deep canyons and rugged 

mountains, some of whose highest summits poke above the water to form the Farallon Islands. 

Biology and Ecological Niches in the Gulf of the Farallones 

Year round, thousands of people are attracted to the cold waters of the Gulf of the Farallones for its whale and bird watching, beautiful 

coastal tide pools, and commercial and sport fishing. Few realize that the organisms that they see and catch are only a small part of a 

rich and complex marine ecosystem. 

Scientists have found that the distribution and abundance of marine flora and fauna in the gulf are directly related to the physical and 

chemical conditions of its waters. Upwelling of deep nutrient-rich waters along the coast during the spring and summer months of most years feeds microscopic plankton that support a complex but fragile web of organisms, from Dungeness crabs, chinook salmon, and brown pelicans 

to elephant seals, great white sharks, and giant blue whales. The Cordell Bank, Gulf of the Farallones, and Monterey Bay National Marine 

Sanctuaries help to protect and manage this marine abundance. 

Issues of Environmental Management in the Gulf of the Farallones 

Since the mid-1800’s, when the California Gold Rush first brought frantic development to the San Francisco Bay region, the waters of the 

bay and of the Gulf of the Farallones, beyond the Golden Gate, have been used to dispose of manmade waste. Perhaps of greatest concern are thousands of barrels of low-level radioactive waste dumped in the gulf during several decades following the Second 

World 

War. Another issue 

is the need to find suitable places in the gulf to dump material dredged from shipping channels in San Francisco Bay. 

To evaluate the hazard from radioactivity to the marine environment, including increasingly important fisheries, scientists have begun 

the search for containers of radioactive waste on the sea floor of the gulf. Studies of the sea floor in the gulf have already enabled the Environmental Protection Agency to designate the Nation’s first deep-ocean disposal site for dredge spoils. 

LABORATORY 

BODEGA 

MARINEEPA