NOAA Technical Memorandum NMFS 

NOVEMBER 1983 

SUMMARY OF ENVIRONMENTAL AND FISHING 

INFORMATION ON GUAM AND THE COMMONWEALTH 

OF THE NORTHERN MARIANA ISLANRS: HISTORICAL 

BACKGROUNDy DESCRIPTION OF THE ISLANDS, 

AND REVIEW OF THE CLIMATE, 

OCEANOGRAPHY, AND SUBMARINE TOPOGRAPHY. 

L. G. Eldredge 

I 

NOAA-TM-MMFS-SWFC-40 

U.S. DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration 

National Marine Fisheries Service 

Southwest Fisheries Center 
NOAA Technical Memorandum NMFS 

The National Oceanic and Atniospheric Adrnintstration (NOAA). organized in 1970, has evolved intoan 

agency which establishes national policies and manages and conserves our oceanic, coastal, and atmospheric resources An organizational element within NOAA, the Office of Fisheries IS responsible for 

fisheries policy and the direction of the National Marine Fisheries Service (NMFS) 

In addition to its formal publications. the NMFS uses the NOAATechnical Memorandum series to issue 

informal scientific and technical publications when complete formal review and editorial processing are 

not appropriate or feasible Documents within this series, however, reflect sound professional work and 

may be referenced in the formal scientific and technical literature 
NOAA Technlcal Memorandum NMFS 

This TM series is WEO lor aoiurnentatlon and timely commt,mcation 01 preliminary results. imterim reports. or 

special curnose i?fornal!in. and have nnt recocved complete formal review. editorial control. or detailed editing 

NOVEMBER 1983 

SUMMARY OF ENVIRONMENTAL AND FISHING 

INFORMATION ON GUAM AND THE COMMONWEALTH 

OF THE NORTHERN MARIANA ISLANDS: HISTORICAL 

BACKGROUND, DESCRIPTION OF THE ISLANDS, 

AND REVIEW OF THE CLIMATE, 

c 

OCEANOGRAPHY, AND SUBMARINE TOPOGRAPHY, 

L. G. Eldredge 

University of Guam 

Marine Laboratory 

UOG Station 

Mangilao, Guam 969 13 

NOAA-TM-NMFS-SWFC-40 

U.S. DEPARTMENT OF COMMERCE 

Malcolm Baldrige. Secretary 

National Oceanic and Atmospheric Administration 

John V. Byrne, Administrator 

National Marine Fisheries Service 

Wllllam G. Gordon, Assistant Admlnlstrator for Flsheries 
PREFACE 

This report was prepared under contract 81-ABA-1658 by Dr. L. G. 

Eldredge. 

published literature and prepare a digest of information on the history of 

Guam and the Commonwealth of the Northern Mariana Islands, on the 

geological formation and description of each island in the archipelago, and 

on the climatic, oceanographic, and submarine topographic features of the 

area. This document is one of two prepared to provide a comprehensive 

overview of the environmental and fishery information that has been 

published to date for the benefit of investigators currently involved in 

the field survey and resource assessment of the Mariana Archipelago. 

Because the report was prepared under contract, the statements, interpretation, and conclusions herein do not necessarily reflect the view of the 

National Marine Fisheries Service. 

The main objectives of the contract work were to review the 

Richard N. Uchida 

Leader, Insular Ecosystem 

Study Program 

November 9 , 1983 
TABLE OF CONTENTS 

Page 

Introduction ......................... 1 

Historical Background ..................... 2 

TheIslands.. ........................ 7 

Guam.......... ................. 8 

Rota................... ........ 9 

Aguijan ......................... 10 

.......................... Tinian 10 

Saipan 11 .......................... .................. Farallon de Medinilla. 13 

Esmeralda Bank and Ruby Volcano. : 14 

14 Anatahan 

Sarigan. 15 

Guguan. 16 

Alamagan 17 

Pagan.. 17 

Agrihan.. ........................ 20 

Asuncion 21 

Maug ........................... 22 

Uracas or Farallon de Pajaros. .............. 24 

Banks.. 25 

........... . ......................... 

......................... 

......................... 

......................... 

......................... 

......................... 

......................... 

Climate.. .......................... 27 

Air Temperature. ..................... 27 

Humidity.. ....................... 28 

Wind..... ...................... 28 

Rainfall ......................... 29 

Storms.. ........................ 29 

Tropical Cyclones. .................... 30 

Chemical Oceanography ..................... 33 

Salinity.. ....................... 33 

Oxygen.. ........................ 34 

Nutrients. ........................ 34 

pH and Alkalinity. .................... 34 

Sea-Surface Temperature .................... 35 

Thermocline.. ...................... 35 

Currents.. .......................... 37 

Surface Currents ..................... 37 

Nearshore Current. .................... 38 

Subtropical Countercurrent ................ 37 

Bottom Topography ....................... 39 

Literature Cited ....................... 40 

List of Footnotes ....................... 51 

Tables ............................ 52 

Figures. ........................... 59 
INTRODUCTION 

The Resource Assessment Investigation of the Mariana Archipelago 

(RAIOMA) Program is a study by the Bonolulu Laboratory which is conducted 

in close cooperation with the Governments of Guam and the Commonwealth of 

the Northern Mariana Islands and by the University of Guam Marine 

Laboratory. 

potential for development of crustacean, bottom fish, seamount 

groundfish, benthopelagic, and pelagic resources over the inner and outer 

shelves, shelf edges, reefs, and slope zones of these islands and 

adjacent seamounts. 

The investigation addresses the problems of determining the 

In an attempt to provide a comprehensive merview of the 

environmental and fishery information that has been published to date, 

this review of the historical background and description of the islands, 

as well as information on climate, oceanography, and submarine 

topography, has been compiled to benefit RAIOMA investigators. Uchida 

(1983) has provided a review of the plankton communities and the fishery 

resources of the same geographic area. 

This review includes environmental information from these islands, 

resulting from six first-hand observations and from letters, notes, and 

other unpublished information from many different visitors. 

is discussed separately, beginning with Guam and moving northward. A 

bibliography of the northern islands (Eldredge 1983) has shown that 

little information is available and published in any language. It is 

anticipated that RAIOMA will provide data for furthering the scientific 

knowledge of these islands. 

oceanography, and bottom topography is drawn from a wide variety of 

literature. 

to the mid-1940s. 

published in Japanese. 

Each island 

The information presented on climate, 

Same of this is rather old, but most of it dates back only 

A little originated before World War I1 and is 

Because of the broad base included here, it is very likely that some 

information may have been overlooked. 

such omissions is urgedto send a note to the author. 

Anyone reading this and finding 

Many people should be acknowledged for their assistance with this 

project. 

many valuable additions and comments. 

Report 83 of the University of Guam Marine Laboratory. 

Numerous individuals have read the manuscript and have made 

This report represents Technical 
2 

HISTORICAL BACKGROUND 

The history of exploration in the Mariana Archipelago can be divided 

into four periods--early, Japanese, American, and recent. 

In the earliest Spanish era, scientific collections were not the 

major effort of travel among the islands. 

arrived on Guam in 1665. 

to Maug during 1668 and 1669 and discovered the remaining northern 

islands, claiming them for Spain. Anson visited Tinian in 1742 and described some of the island's features, including the wells and archaeological remains. La Perouse (1797) stopped briefly at Asuncion in 1786 and 

noted some plants. 

led by Alessandro Malaspina in 1792. 

by the naturalists and him were never fully completed. 

aboard H.M.S. Blossom, visited Asuncion in 1827 and further described the 

vegetation sin a general manner. 

Diego Luis de Sanvitores first 

He travelled north throughout the archipelago 

The first scientific expedition in the Marianas was 

Beechey (1831), 

He visited only Guam, but reports 

Otto von Kotzebue, a Russian, and several naturalists visited Guam 

in November 1817 for six days. 

at Guam and remained there for several months. 

Gaimard and botanist Gaudichaud collected extensively. 

Rota and Tinian. Fedor von Lutke with ornithologist F. H. de Kittlitz 

landed at Guam briefly in March 1828 aboard the Astrolabe under the 

command of Dumont d'urville. 

In March 1819 Louis de Freycinet stopped 

They also visited 

Zoologists Quoy and 

It was not until the late 1880s that definitive efforts were made to 

collect scientific information about the northern islands. Don Eugenio 

Sanchez y Zayas sailed throughout the islands with the Governor of the 

Marianas in early 1866 aboard the Narvaez. He prepared a detailed study 

of the islands which appeared soon after (Sanchez y Zayas 1866). In the 

early 1870s Governor Don Luis de Ibanez y Garcia visited the islands and 

wrote a history and description of them (Ibanez y Garcia 1866). 

Marche travelled throughout the islands and collected information and 

specimens between April 1887 and March 1889. 

Mariana Islands as far north as Agrihan (Marche 1890, 1891). His 

collections resulted in additional publications on fish (Pellegrin 1898), 

birds and mammals (Oustalet 1895), and land snails (Quadras and von 

Moellendorff 1894). During May 1901, G. Fritz travelled to all the 

northern islands and described their general geology and flora. He 

planted coconuts, ironwood trees (Casuarina), and other plants on Guguan 

and Uracas. His report (Fritz 1902) served as the basis for several 

which followed. One of the most extensive works pertains to all the 

German islands of the Marianas (Prowazek 1913); however, much of the 

natural history is drawn from Fritz (1902). Prowazek described Rota, 

Tinian, and Saipan and provided an extensive list of the terrestrial 

flora. 

Alfred 

He visited most of the 
3 

Alexander Agassiz, aboard the Albatross, led the first American 

expedition to Guam in 1900. 

ones on fishes, birds, crustaceans, and sea cucumbers (Agassiz 1903). 

Alvin Seale from the B. P. Bishop Museum also visited Guam in 1900 and 

collected a number of birds and fishes (Seale 1901). One of the first 

general accounts of the Marianas was that of Costenoble (1905). 

Numerous reports have resulted which include 

During the Japanese administration of the Marianas, a number of surveys and reports were published pertaining to botany and geology. Tayama 

'(1936) dealt extensively with the geology and coral reefs of the islands, 

and Yoshii (1936) described the noncalcareous rocks of Pagan and other 

islands. Tanakadate (1940) visited Pagan and wrote a detailed description of the volcanos of that island. 

R. Kanehira and R. Hosokawa at many of the islands (Kanehira 1934, 

Hosokawa 1934). 

time (Nishiyama 1942). 

Botanical aollections were made by 

Only one marine animal was reported upon during this 

Following World War 11, members of the Pacific Vegetation Project, 

including D. Andersdn (in 1949) and F. R. Fosberg (in 19501, visited 

several islands, In 1949 Y. Kondo visited Pagan and Alamagan and collected land snails, including Partula gibba (Kondo 1970). 

field work began in 1952 when J. T. Stark and J. I. Tracey. Jr. visited 

Geological 

__ Pagan to investigate the sulfur content of the inner lake. During the 

summer of 1954 a team of field workers carried out the study which led to 

the publication of "Military Geology of Pagan" (Corwin et al. 1957). 

Although primarily a geological study, a number of natural history 

specimens were collected. These included plants, insects, land snails, 

and other organisms. 

northern islands. Fosberg (1958) and Fosberg and Corwin (1958) reported 

on the plants, 

the Smithsonian Institution appear in various issues of "Indo-Pacif ic 

Mollusca," Similar military geological studies were carried out at Guam 

(Tracey et al. 1959), Tinian (Doan et al. 19601, and Saipan (Cloud 1955). 

The report is the most extensive one for any of the 

Reports on marine gastropods collected and deposited in 

The University of Guam Marine Laboratory was established in 1970 to 

carry out, in part, marine research in the archipelago, especially at 

Guam. To date the Laboratory has a list of 179 contributions and 81 

technical reports. 

More recently there have been several short trips to a number of 

islands. J. Villagomez of Saipan visited Pagan in July 1970 and collected algae and invertebrates. In February 1973, R. S. Jones, K. H. 

Randall, H. Kami, and R. Struck of the University of Guam and Guam's 

Divison of Aquatic and Wildlife Resources travelled to Maug, Agrihan, and 

Anatahan aboard the U.S.S. Grasp. 

marily, as well as some algae and invertebrates. 

They collected fishes and corals pri- 
4 

During 1971 the privately owned ketch Wanderer skippered by R. 

Hervin sailed to all the islands. In April 1971 the survey group visited 

only Pagan; in June 1971 and in July 1972 several other islands were surveyed, 

brates (mainly opisthobranch mollusks), and fishes were collected. 

During all of these cruises algae, terrestrial plants, inverteThe National Oceanic and Atmospheric Administration (NOAA) ship 

Townsend Cromwell cruised throughout the islands in April and October 

1971 and took depth and temperature measurement which formed the basis 

for a report on the physical oceanography of the northern islands 

(deWitt 1972). 

hydrographic cruises which had taken place in these northern islands 

between 1936 and 1968. 

DeWitt also listed 35 known Japanese and Russian 

In January 1975 the University of Guam Marine Labokatory conducted 

The major objective was a broad-based marine survey. 

the first of two trips throughout the entire chain aboard the schooner 

L_- New World. This 

survey group included L. G. Eldredge and nine University students. 

During July of the same year, the New World again sailed to Uracas. 

time L. G, Eldredge was joined by S. Amesbury of the University of Guam, 

E. A. Kay and C. Lamoureux of the University of Hawaii, and M. Falanruw 

of the Yap Institute of Natural Science, as well as five students. The 

second trip included some detailed terrestrial investigations. The algae 

have been reported by Tsuda and Tobias (1977a, 1977b) and the terrestrial 

plants by Fosberg et al. (1977). 

appeared (Eldredge 1975, Ronck 1975). 

-- This 

Popular accounts of these trips have 

A general account of all the Northern Marianas was published by 

Lehne and Gabler (1972). A report on the vascular flora (Fosberg et al. 

1975) with additions, and one concerning the megapode (Falanruw 1975) 

have also been published. 

In 1974 a team of geologists from the University of Arizona made 

short stops at Sarigan, Guguan, Pagan, and Asuncion but remained at 

Agrihan for about two-and-a-half weeks. 

group 

Alamagan. 

that summer. 

Anatahan. 

In the summer of 1978 another 

spent 3 weeks each at Sarigan (Meijer and Reagan 1982) and 

They also visited most of the other islands briefly during 

In 1979 they returned and spent some time at Guguan and 

Further investigations have been carried out at Guam. 

In August 1976 the Lindblad Explorer with Sir Peter Scott and R, and 

V. Taylor aboard spent one day at Maug. In a report to the Resident 

Commissioner (Lindblad Explorer 19761, they sight-recorded 113 species of 

reef fish and recommended that the island be protected. A similar report 

followed their brief 1977 visit (Lindblad Explorer 1977). 

Between 23 and 26 November 1977, five biologists from Guam, (R. T. 

Tsuda, L. G. Eldredge, P. Moore, M. Chemin, and S. Neudecker) visited 

Maug and conducted a natural history survey (Eldredge et al. 1977). 

At the request of the Trust Territory of the Pacific Islands government, the Japan Marine Fishery Research Center conducted skipjack tuna 

pole-and-line fishery surveys (Japan Marine Fishery Research Center 1975, 

1976, 1977) aboard the No. 20 Akitsu-Maru. Included in the survey 
5 

results are temperature profiles to depths of 250 m. 

bottom-handline fishing survey was conducted by the Micronesian 

Coordinated Development Co., Ltd. in 1976. 

the Daikatsu-Maru which visited Pagan, Agrihan, Asuncion, and Maug, as 

well as the southern islands (Micronesian Coordinated Development Co. 

1976). 

Additionally, a 

The survey was carried out on 

The U.S. Army Crops of Engineers sponsored a survey of the wetlands 

of Guam, Tinian, and Saipan in 1977 (Moore et al. 1977). In 1979 an 

ornithological survey was conducted at Guam, Tinian, Saipan, and Pagan 

(Tenorio and Associates 1979). 

from Pagan (Fosberg et al. 1980). 

Additional vascular plants were reported 

During July 1978 the Commonwealth of the Northern Marianas sponsored 

a trip on the MV Olwol which included members from the Coastal Resources 

Management, Environmental Protection Agency, Historic Preservation 

Agency, and the U.S. Fish and Wildlife Service offices. They briefly 

visited all the islands. 

In the summer of 1979, R. B. Clapp (U.S. Fish and Wildlife Service) 

visited six islands. He recorded several new bird didtributional 

records, collected specimens for taxonomic investigations, and noted 

range extensions. Reptiles and mammals were also collected. 

The RV Townsend Cromwell visited almost all the islands of the 

archipelago again during the summer of 1978. 

Pacific Tuna Development Foundation, the FV Typhoon carried out 8 months 

of exploratory fishing (May 1980-January 1981). Almost a11 the island 

areas, banks, and seamounts were sampled during that time. A wide 

variety of methods was used and a number of different fishes were 

collected (Hosmer and Kami 1981). 

activity in early 1981 at Guam and around Tinian and Saipan. 

Under the auspices of the 

The FV Typhoon also conducted ffshery 

In March 1981 eight University of Guam biologists visited Pagan 

under the auspices of the Commonwealth Office of Coastal Resources , 

Management. The major objective of the project was a general natural 

history survey of the island to include marine studies, as well as 

wildlife, plant and lake investigations. Two months after the May 21 

volcanic eruption, most of the same biologists returned to Pagan to 

survey the impact of the ash and scoria and lava flows. 

briefly reported these findings. 

Eldredge (1982) 

The U.S. Fish and Wildlife Service and the Guam Aquatic and Wildlife 

Resources Division conducted a survey of the distribution and abundance 

of forest birds at Guam during June 1981. 

similar study in cooperation with the Commonwealth Division of Fish and 

,Game, was Conducted on Rota, Tinian, Aguijan, Naftan, and Saipan. 

Extensive plant collections were also made at that time. 

Between March and June 1982 a 

In 1982 the National Marine Fisheries Service, Southwest Fisheries 

Center, Honolulu Laboratory initiated the Resource Assessment Investigation of the Mariana Archipelago (RAIOMA). 

the RV Townsend Cromwell particiated in three extensive cruises (cruises 

82-02, 82-03, 82-04) throughout the Archipelago. 

Between April and August 1982; 

Bathymetric surveys 
6 

were conducted and chartlets of twelve banks and pinnacles have been 

produced (Polovina and Roush 1982). 

1983 and early 1984. 

A similar survey is planned for late 

During April 1983 five members of the University of Guam Marine 

Laboratory aboard the FV Pution Ta'se conducted an inshore environmental 

assessment, plankton survey, and preliminary precious coral dredging 

under the auspices of the Office of Sea Grant Programs around Pagan, 

Guguan, Anatahan, Saipan, and Aguijan and in July 1983 around Rota. 

Similar studies had been completed at Guam during the fall of 1982. 

conjunction with these studies, a bibliography of the islands of the 

Active Arch (Esmeralda to Uracas) has been prepared (Eldredge 1983). 

In 
7 

THE ISLANDS 

The islands of the Mariana Archipelago lie between lat. 13" and 20" 

N and are divided into two somewhat parallel arcs (Figure 1). 

islands have also been referred to as the Ladrones Islands, Island de 10s 

Velas Latinos, Los Jardines, Los Prazeras, 1'Archipel de St, Lazare, and 

les Iles Marianes (Bryan 1943). The outer or frontal arc is composed of 

the more southerly limestone islands of Guam, Rota, Aguijan, Tinian, 

Saipan, and Farallon de Medinilla. 

from Esmeralda Bank and Ruby Volcano to Farallon de Pajaros (Uracas). 

These are the only active vo:.canic islands in Micronesia and among them 

Agrihan is the highest. 

volcanically active during h-storic times. 

The 

The inner or active arc extends north 

Mosi: of these latter islands have been 

The archipelago consists of two separate political entities. 

the largest and southernmost, is an unincorporated territory of the 

United States. The remaining islands comprise the Commonwealth of the 

Northern Mariana Islands. 

Guam, 

Environmentally, a number of general publications refer to several 

islands of the entire archipelago. Earlier reports are those of Corte 

(1875) and Sanchez y Zayas (1866); Marche travelled widely and reported 

on several islands (Marche 1890, 1891). Following the Treaty of 

Versailles, the islands north of Guam became politically distinct from 

Guam. Fritz (1902) visited all the islands. His report was the basis 

for much of Prowazek's (1913) "Die deutschen Marianen." Lehne and Gabler 

(1972) summarized most of the more recent information, reporting on each 

island individually, providing brief notes on history, population, and 

physical features. Very few scientific investigations were carried out 

on Guam during the U.S. Naval administration other than the monumental 

botanical study by Safford (1905). 

During the last 30 years, more biological information has been made 

available. Baker (1951) reported on all the birds of Micronesia, 

including those of the Marianas. Owen (1977) compiled a checklist of the 

birds by major island group--Marianas--rather than by specific island. 

Pratt et al. (1979) updated much information about native birds of the 

more southern islands. 

Safford (1905) was among the first to detail the plants of Guam. 

- The vegetation was described by Fosberg (1960) and Fosberg et al. (1975, 

1977, 1980). Moore et al. (1977) mapped and inventoried wetlands on 

Guam, Tinian, and Saipan. 

Land snails of the family Partulidae were described from Guam and 

Saipan by Crampton (1924) and further noted by Kondo (1970) including 

records from Aguijan, and Pagan. 

Few marine investigations have covered more than one island. 

sive (military) geological studies have been conducted at Guam, Tinian, 

Saipan, and Pagan, and these reports contain a wide,variety of information some of which is also available in several different research publication series, 

ExtenEldredge and Randall (1980) prepared an atlas of the 
8 

reefs and beaches of Rota, Tinian, and Saipan, as well as Aguijari and 

Farallon de Medinilla. They conducted a similar survey at Guam (Randall 

and Eldredge 1976). 

The benthic algae is the only group which is widely known from 

throughout the northern islands (Tsuda and Tobias 1977a, 1977b). Corals, 

gastropods, crustaceans, and fishes from a wide variety of islands are 

pres en t ly be in g studied . 

An integrated review of seven of the islands of the archipelago has 

been prepared in support of the National Park Service Natural Landmarks 

Program (Abbott et al. 1982). Potential National Natural Landmarks are 

evaluated, and Guguan, Alamagan, Pagan, Agrihan, Asuncion, and TJracas, as 

well as the northern tip of Saipan are proposed. On Guam four existing 

sites--Puntan dos Amantes, Facpi Point, Fouha Point, and Mount 

Lamlam--are reviewed and two--Cocos Lagoon and Pati Point--are proposed. 

A number of sites have also been proposed as Marine Sanctuaries under the 

1972 Marine Protection Research and Sanctuaries Act administered by the 

National Oceanographic and Atmospheric Administration. 

The islands north of Saipan have historically been referred to as 

the "Gani" (Le Gobien 1701). 

Saipan and later in 1698 to Guam and remained that way, apparently, until 

the late 1800s. Sanchez y Zayas (1866) remarked specifically that no 

inhabitants were seen at Agrihan. Corte (1875) does not refer to any. 

During his visit, Fritz (1902) reported on small populations. 

These islands were depopulated in 1695 to 

Environmental information for these islands is very incomplete. 

First-hand observations from six visits, as well as from letters, notes, 

and so forth provided by other visitors form the basis for most of the 

information provided here for the "Gani. I' 

Each island is discussed separately beginning at the south and 

moving toward the north. 

GUAM 

Guam is the largest island of the archipelago (Figure 2). It is 

located at lat. 13"28'N and long. 144"45'E. The highest elevation is 405 

m (1328 ft), and the total area is 637 sq. km (246 sq. mi), 10% of which 

are reefs and lagoons. The island has been previously known as Guahan, 

Gujan, Guan, Gwan, San Juan, Guahan, Gujan, Guan, Gwan, San Juan, I. de 

St. Jean, Omia Jima (Bryan 1943). 

A limestone plateau covers most of the northern half of the island. 

The southern half is composed of volcanic material and edged at most 

places with low, raised limestone. Fringing reefs surround most of the 

island. Barrier reefs are found at Cocos Lagoon and at Apra Harbor 

(Figure 3). Twelve small islets are found along the reefs. Cocos 

Island, at the southern end of Guam, is the largest. 

Guam is the most well known island of the Marianas. Several studies 

have contributed to the knowledge of the coastal and reef areas. me of 

the first of these was a coastal survey conducted by Randall and Holloman 

(1974) who divided the island into 12 coastal sectors. They detailed the 
9 

coastal features of each, especially the geological units, soils,' and 

hydrology. A selected bibliography and a review of the physical, 

chemical, and biological oceanographic literature for the waters 

surrounding Guam have been prepared (Eldredge and Kropp 1981 and MS ). 

Information about the island is summarized here. 

1 

Most of the beaches of Guam are composed of light-colored, calcareous sands, although a few in the south have dark-colored volcanic sand. 

Emery (1962) conducted an anlaysis of 58 beaches, and Randall and 

Eldredge (1976) mapped and noted the characteristics of the island's 

beaches. Shoreward of the beach, the narrow band of vegetation is called 

"the strand. Fosberg (1960) described strand vegetation, and Falanruw 

(1977) discussed the role of the strand in relation to the beach. 

Much of Guam's coastline is outlined with rocky intertidal areas. 

Limestone and volcanic boulders are scattered on reef flats or are 

buttressed along raised headlands. Boulders are also predominant in 

areas of artificially filled shoreline. Nips are characteristic 

indentations found along rocky headlands. At sea-level wave-washed 

benches are located at several locations (Randall and Eldredge 1976). 

Seagrass stands cover approximately 9% of the fringing and barrier 

reefs (Sealand 1978). Three species of seagrasses are known (Tsuda et 

al. 1977, Tsuda 1981). The distribution of these species has been mapped 

(Randall and Eldredge 1976). 

Land birds have been described by Baker (1951), Pratt et al. (1979), 

and by ongoing studies at Guam's Division of Aquatic and Wildlife 

Resources. Fosberg (1960) described the vegetabtion, and Stone (1970) 

prepared a flora of the island. 

Moore et al. (1977) described most of the wetlands along the shore and 

inland, and Best and Davidson (1981) inventoried the island's aquatic 

ecosystems. 

Wilder (1976) mapped the estuaries, 

ROTA 

The southernmost island of the Commonwealth of the Northern Mariana 

Islands, Rota (Figure 4) is located at lat. 14°07'-14012'N and long. 

145°07'-145018'E. The island has an elevation of 491 m (1612 ft) and an 

area of 85.2 sq. km (32.9 sq. mi). It has been previously known as Bota, 

Botah, Ile Sainte Anne, Isla de Rota, Luta I., Rota To, Santa Ana, Sapan, 

Sarpan, Sarpana, O'Rota, Sarpanta, Serpana, Zarpana, Zarpana, Zarpane 

(Bryan 1971). 

The coastal area of Rota, which is composed entirely of raised 

limestone, has been completely mapped by Eldredge and Randall (1980). 

Steep cliffs and slopes edged by a sea-level bench are found along the 

southeastern shoreline (Figure S), as well as around the southwestern 

peninsula. 

southernmost area, depositing some volcanic material which originated 

from the higher, interior lands. 

A reef flat, as wide as 250 m, is the main feature of the northSeveral intermittent streams flow to the coast at the 

western shore. Most of this reef flat is narrower and raised slightly. 
10 

An irregular band of raised limestone is found along the outer margin of 

the reef flat. (This feature is found only at Rota.) Two somewhat 

parallel bands of this raised limestone are found toward the north. One 

is along the inner part of the platform and the other toward the outer 

part. In general the reef is relatively flat with occasional boulders 

and depressions containing sand and rubble (Eldredge and Randall 1980). 

The shore is composed mainly of beachrock and intermittent raised 

limestone patches. Coral-algal-mollusk rubble and sand beaches are rare 

but may be found scattered among limestone patches. 

The biota of Rota is not well known. An informal biological expedition was conducted by the Department of Biosciences, University of Guam 

in 1969 (Tsuda 1969a). More than 80 species of benthic algae have been 

reported (Tsuda 1969b). Seagrasses were reported by Eldredge and Randall 

(1980) for the first time. Nearly 150 species of fishes are known (Jones 

1969). Numerous corals have been collected. 

Land birds have been described by Baker (1951) and more recent 

records added by Pratt et al. (1979). Fosberg (1960) reported on the 

vegetation. 

AGUIJAN 

This small precipitous island is located at lat. 14'51" and long. 

145"34'E (Figure 1). The island has an elevation of.168 m (504 ft) and 

an area of 7.2 sq. km (2.7 sq. mi). It has been previously known as 

Agaigan To , Agiguan Insel, Agrigan , Aguigan , Aguiguan , Aguij an , Aguijon , Ile de Saint Angel, Santa Angel, and Santo Angel (Bryan 1971). 

Aguijan is a nearly flat plateau composed entirely of limestone and 

surrounded by steep vertical cliffs with large limestone blocks at 

places, especially along the eastern shore. A narrow, sea-level bench is 

also found along the eastern side (Eldredge and Randall 1980). 

reconnaissance geological survey was conducted by Burke et al. (1951) who 

described the limestone nature of the island. 

A 

No wide reef flats occur. Coral is diverse and actively growing in 

different areas. Tsuda (1971) noted that the only area which might be 

considered a coral reef occurred 1 km (0.6 mi) south of the northernmost 

tip of the island. 

Naftan Rock (or Nafutan) is located off the southern end. This 

limestone pinnacle has an elevation of about 20 m (59 ft). 

noted and plants collected during the spring 1982 U.S. Fish and Wildlife 

survey. 

Birds were 

TINIAN 

This relatively flat island lies about 9.2 km (5 mi) southwest of 

Saipan (Figure 6). It is located at lat. 14°55'-15006'N and long. 

145°35'-145041'E. The highest elevation is 178 m (584 ft), and the total 

area is 101.7 sq. km (39.3 sq. mi). The island has been previously known 

as Bona Vista, Buenavista, Ile de Bonavista, Tanian, Tenian To, Tinian 
11 

Insel, Tinianion, and Zinian (Bryan 1971). 

Tinian's raised limestone is a result of complex block movement, 

sedimentation, and differential coral-reef growth (Doan et al, 1960). 

The entire shoreline has been described and mapped (Eldredge and Randall 

1980). Most of the island is surrounded by low to high cliffs, many 

undercut at sea level. The southern and southeastern coasts are the 

highest and are nearly vertical. 

around the island, although slumping has occurred in places. Large 

blocks and boulders buttress the cliffs. At a fault at Unai Chiget, the 

cliffs decrease in height and numerous blowholes and pools are found 

along the shore. Sea-level, wave-cut, notches or nips are found around 

the shore. 

A sea-level bench is found nearly all 

Beaches are not well developed except at Unai Dankulu (Figure 7) and 

at Tinian Harbor. Most are narrow with intermittent raised limestone. 

The calcareous sand is mixed with coral-algal-mollusk rubble. 

The reef flats are generally narrow, varying in width from less than 

15 m to 180 m (50 to 590 ft) at Tinian Harbor. Most have a shallow, 

irregular surface and a grooved margin. 

the southwest shore near the Tinian Harbor. It is oval in outline and 

has an irregular reef-rock surface with some patches of sand, gravel, and 

rubble. 

attached to the shore by a fringing reef. 

seven meters (23 ft) deep (Doan et al. 1960), has.also been altered with 

the construction of shore-side and finger-pier docking facilities. 

One patch reef is located along 

A barrier reef, now altered as a breakwater for the harbor, is 

The lagoon, originally about 

As part of an environmental impact survey, Jones et al. (1974) carried out extensive field studies at four sites at Tinian. 

the coastal and submarine physiography, conducted preliminary in-shore 

current studies, and recorded a total of 246 species of fishes, either 

observed or collected, 84 species of benthic algae, 129 species of 

corals, 36 species of gastropods, 21 species of echinoderms, as well as 

other marine invertebrates. 

They described 

On land, the vegetation has been described by Fosberg (1960). Moore 

et al. (1977) mapped the wetlands at Hagoi on the northwestern plateau 

and Magpo on the south central area. They also inventoried the wetland 

vegetation. In addition to Baker (1951) and Owen (1977), information on 

bird populations is provided by Pratt et al. (1979) who reported that the 

Tinian monarch, Monarcha takatsukasea, thought to be decreasing in 

numbers, was very abundant. 

SAIPAN 

Saipan, the largest island in the Commonwealth of the Northern 

Mariana Islands, is located at lat. 15°05'-15017'N and long. 145"41- 

145'50'E (Figure 8). Mt. Tagpochau, the highest elevation on Saipan, is 

765 m (1554 ft). The island has an area of 120.6 sq. km (46.5 sq. mi) 

and has been previously known as Ile de Saint Joseph, Saepan, Saespara, 

Saipan Insel, Saipan To, San Jose, Saspan, Seipan, Sepan, Sespan, Swypan, 

Supan, Zeipan, and Zerpan (Bryan 1971). 
12 

Saipan is a complex island of dacitic and andesitic lava covered at 

most places by a variety of limestones and limestone-associated calcareous materials (Cloud et al. 1956). Volcanic material is exposed along 

the shore only on the east coast at Puntan Fanunchuluyan and Isleta Maigo 

Fahang (Bird Island) (Figure 9), near Puntan Hagman, and north of Puntan 

I Naftan. The remainder of the shore is limestone (Eldredge and Randall 

1980). 

Most of the coast is lined with low to steep headlands and cliffs. 

Much of it is buttressed with blocks and boulders. Raised limestone is 

landward of the reef flats at most places. 

barrier lagoon along the western shore. 

of sand and gravel. All are composed of coral-algal-mollusk rubble. 

Mixed volcanic material is also present at the intermittent stream mouths 

along the east coast. 

Eldredge and Randall (1980). Cloud (1955) analyzed the entire coast for 

military purposes and provided a map which related the degree of accessibility for each part of the shore. 

Fine-sand beaches rim the 

Most other beaches are composed 

The shore has been described and mapped by 

The barrier reef with its associated lagoon is a major feature of 

Saipan. It extends along almost all the west coast and is wider and 

deeper in the northern half. Cloud (1959) carried out extensive field 

studies in the lagoon. He described habitats and established 16 

different biotopes to identify these different habitats. Amesbury et al. 

(1979) used these same habitats for his survey of the fish resources of 

the lagoon. The lagoon has been mapped in detail thr,ough an analysis of 

aerial photographs, maps, and first-hand observations (Eldredge and 

Randall 1980). 

In addition to Cloud's (1959) survey of the lagoon which included a 

tabular listing of nearly 700 species of organisms identified from each 

biotope, Goreau et al. (1972) examined 40 reef sites in relation to the 

probable effects caused by the crown-of-thorns starfish, Acanthaster 

planci. The survey by Goreau et al. included extensive observations on 

the cushion star, Culcita novaeguineae. Population, behavior, and 

selective feeding were noted as they related to the overall community 

structure. A definition of reef terms for Saipan was also provided. 

Along the shore Doty and Marsh (1977) conducted surveys between Unai 

Sadag Tase and the seaplane ramp at Puntan Flores. They were investigating the impact of the power barge "Impedence." These were the first 

quantitative measurements made in the area, Sediments, currents, and 

physical and chemical characteristics are reported. Biological investigations included algae, seagrasses, invertebrates, fish, and plankton. 

Amesbury and Doty (1977) noted the differences between the plankton from 

the inner and outer parts of the harbor and suggested that there might be 

only a little mixing between the two areas. 

A small islet, Managaha, is a major feature just outside the 

westernmost part of the barrier reef. This low islet is heavily 

vegetated and now a cultural preserve under the Mariana Islands 

Constitution. 

Fringing reefs vary in width to nearly 200 m at Bird Island. Most 

are relatively flat with exposed blocks and boulders at places. Corals 

are widely scattered and common on deeper reef flats. Their relative 
13 

abundance is shown for all areas (Eldredge and Randall 1980). 

Seagrasses are apredo-ant feature of the barrier lagoon. A mixture of three species carpets the entire bottom in places, especially in 

the southern half (Tsuda et al. 1977). The relative abundance and 

distribution of seagrasses are also shown by Eldredge and Randall (1980). 

On land, the vegetation has been described by Fosberg (1960). Moore 

et al. (1977) mapped and inventoried seven wetland sites, of which the 

largest was Susupe Marsh. 

near the commercial facilities in the barrier lagoon. 

described by Baker (1951). Recently Pratt and Bruner (1978) rediscovered 

the megapode from areas at the northern end and along the eastern side. 

Pratt et al. (1979) described the present status of many of the endemic 

species. 

They noted the very restricted mangrove areas 

The birds were 

FARALLON DE MEDINILLA 

Located approximately 83 km (45 mi) northeast of Saipan, this precipitously raised limestone island lies generally in a northeast-southwest 

direction (Figure 10). It is located at lat. 16"Ol'N and long. 146"05'E, 

its highest elevation is about 81 m (266 ft); Fritz (1902) reported the 

highest elevation as 30 m (98 ft) high. 

0.9 sq. km (0.35 sq. mi), It has been previously known as Bad0 Shima, 

Bird I., Farallon Paxaros, Island Pexaros, Madinilla, Medeinizya, 

Medinija To, Medinilla I., Medinizea, Medinizya To, Paxaros, Rocher, 

Rocker, Urasas, and Urakas (Bryan 1971). 

The area of the island is about 

This island is the least known of the southern limestone islands. 

Although the actual discovery date of the island is unknown, the French 

explorer Freycinet noted the island in 1819. Corte (1875) referred to it 

as a bare table land. Fritz (1902) landed on the island, climbed to the 

top and reported on the low brush and vegetation. 

In their atlas, Eldredge and Randall (1980) represented the island 

At 

as having nearly vertical cliffs with some slumping along the northeastern shore. 

various areas of the island large blocks and boulders have eroded and 

formed small islets. 

They provided three photographs and an outline map. 

The island has been a bombardment range for the U.S. Navy and Air 

*- Force since 1971. The U.S. Navy (1974) prepared a Draft Environmental 

Impact Statement and a Navy team made a very brief visit to the island 

via helicopter. Their report does not mention specific organisms. 

In general, Farallon de Medinilla is the only island in the archipelago from which no, or very few, biological specimens have been collected. 

A 20-fathom shoal area is present about 1.8 km (1 mi) north of the 

island. The banks surrounding the island have recently been charted 

(Polovina and Roush 1982). 
14 

ESMERALDA BANK and RUBY VOLCANO 

Two active volcanoes are located at the southern end of the active 

or inner arc. Esmeralda, the more southern, rises to within 30 m (98 ft) 

of the surface. The diameter at the base of this 1,300-m (4,264 ft) high 

volcano is 9 km (14.5 mi). 

ft) deep and 2 km (3.2 mi) across (Stem and Bibee 1980). 2The most 

recently reported eruption of Esmeralda was in April 1982. 

water bubbling and steam vapor were observed. During an April 1975 

eruption, the discolored boiling spots were observed in a north-south 

pattern (Figure 11). Gavrilenko et al. (1980) and Gavrilenko (1981) 

reported on a January 1978 eruption. 

mapped by Polovina and Roush (1982). 

It has a central caldera which is 300 m (984 

Surface 

The topography of the Bank has been 

The other, Ruby Volcano, was first named following an April-May 1966 

eruption (Johnson 1973). Sofar hydrophones located at Enewetak Atoll and 

Wake Island recorded background noise which showed an origin at lat. 

15'10'N and long. 145'54'E. This volcano has a depth of about 210 m 

(689 ft). 

ANATAHAN 

Anatahan, the southernmost of the northern islands, is located at 

lat. 16'22" and long. 145"40'E (Figure 12) and has an elevation of 788 m 

(2,585 ft) and an area of 32.3 sq. km (12.5 sq. mi). It has been 

previously known as Amalgam, Anatacan, Anatahan Insel, Anatahan To, 

Anatahan, Anatans, Anataxam, Anataxan, Anatayan, Anathahun, Anatjan, 

Anatiajan, Ile de San Joachim, Inatajan, Matan, Natan, San Joaquin, and 

San Joaquine (Bryan 1971). 

Anatahan is unusual in that its shape is basically rectangular; its 

longer axis is oriented east-west. High, irregularly sculptured land 

slopes toward the water from the craters of two extinct volcanoes (Figure 

13). No volcanic activity has been reported during historic times. 

Recently dated rocks from the northern coast show them to be the oldest 

reported from the northern islands. 

Steep cliffs and headlands outline most of the shore. Large rounded 

blocks and boulders buttress cliffs in areas somewhat protected. At the 

"Obs. Spot" on the navigational chart, (DMA Chart No. 81086) the shore 

is composed of rounded, irregularly placed boulders as large as 0.5 m 

(1.6 ft), which form one or two high berms depending on surf conditions. 

Immediately to the north low headlands gradually become volcanic buttresses 

with shallow tide pools landward. Very few, widely scattered areas have 

small grain-sized sand beaches. Truncated basaltic platforms occur along 

the southwestern shoreline. 

Along the high intertidal zone the gastropods Littorina pintado and 

Nerita plicata were relatively common. On the upper surfaces at the 

water level, the snail Purpura persica was also relatively abundant. 

This snail was found commonly throughout the northern islands, although 

it rarely occurs at Saipan and Guam. 

In deeper water large rounded blocks and boulders and isolated sand 
15 

patches can be seen. 

upper surfaces of these blocks and boulders. 

riant. 

Isolated corals are found widely scattered on the 

Coral growth is not luxuMore than 120 species of terrestrial plants have been reported 

(Fosberg et al. 1975). Specimens were also collected in July 1981. 

Birds are not abundant. As many as 20 to 30 fruit bats could be counted 

at a time. Goats are very common. 

Curiously, Anatahan was the site of an interesting drama from 1944 

to 1951. 

of World War 11. Their plight was described by Maruyama (1954) and later 

made into a movie. 

Several Japanese nationals were stranded on the island because 

SARIGAN 

Sarigan, an extinct volcano, is located at lat. 16'42" and long. 

145'47'E (Figure 14). The elevation is 549 m (1,801 ft), and the area is 

5 sq. km (1.9 sq. mi). The island has been previously known as 

Chereguam, Cherega, Cheregua, Cheroga, Cheruguan, Ile de Saint Charles, 

San Carlos, Sarigan Insel, Sarignan, Sarigoan, Sariguan, Seriguwan, and 

Sarigwan To (Bryan 1971). 

Of all the northern islands, Sarigan is one which has no historically recorded volcanic activity. 

The shoreline is made up primarily of high cliffs and steep slopes. 

Low, irregular lava is located along the southwest coast. Much of the 

uplands appear to be in various stages of erosion (Figure 15). 

Almost nothing is known about the marine biota; nothing has been 

published. 

(Fosberg et al. 1975). Baker (1951) listed he birds known to occur. 

During a visit in the summer of 1978, Ludwig reported that megapodes 

were relatively abundant, based on the 10 to 15 adults he saw during a 

single hike. 

limited flying by some individuals. Fritz (1902) noted seeing large 

11 countless" nu9ers of seabirds; however, similar observations were not 

made by Ludwig. 

On land, 128 species of vascular plants have been reported 

5 

He also commented on seeing some behavioral interaction and 

4 N merous goats were seen in January 1975 and again in July 1978 by 

** Y Ludwig who counted as many as 50 at a time grazing on the slopes. 

3 Both Fritz (1902) and Ludwig noted extensive archaeological 

material, including latte stones and pottery. 

Along with Maug, this island is protected as an uninhabited island 

to be "used only for the preservation of birds, fish, wildlife and plant 

species" by the Constitution of the Commonwealth of the Northern Mariana 

Islands (Article XIV, Natural Resources), marine resources (Section 1) 

and uninhabited islands (Section 2). 
16 

GUGUAN 

Guguan is a complex island with a barren active volcano and an old 

vegetation-covered cone. 

145"51'E (Figure 16). 

m (988 ft), and its total area is 4.2 sq. km (1.6 sq. mi). It has been 

previously known as Gaugan, Giges, Gregan, Greguan, Grijes, Guagan, 

Guegon, Gugan, Gugua, Guguam, Guguan Insel, Guguwan, Guan To, Ile de 

Sainte Philippe, Saint Philips, San Falipe, San Felipe, and San Filipe 

(Bryan 1971). 

The island is located at lat. 17'19" and long. 

Its highest elevation at the southern half is 301 

Reported dates of volcanic activity vary. Tanakadate (1940) 

reported eruptions in 1819 and 1901, and Corwin' reported minor activity 

in the 1860s and explosive activity in the 1880s. The volcano is still 

active because in 1975 steam was intermittently being emitted from the 

northern cone which is syrrounded by a crust of yellowish sulfur-like 

material; however Ludwig 

his summer 1978 visit. 

shallow depths. 

did not observe any steam being emitted during 

Along the west coast warm sand was felt at 

The shoreline is very irregular; most of it is steep cliffs, At 

areas along the southwest shore, low truncated basaltic platforms are 

found. Between two 15-m (49.2 ft) headlands along the west coast is a 

narrow, round boulder and cobble shore which is quite well protected and 

would generally afford the best landing site, depending on sea-state conditions. A small embayment surrounded by vertical cliffs, presumably t e 

remnants of a volcanic cone, is located along the east coast. 

observations were made along the east coast; the other ones have been 

made along the west coast. To the north and northwest the shore is 

composed of vertical cliffs buttressed with eroded blocks which have 

sharp, uneroded sides. A lava flow enters the water along the northwest 

shore (Figure 17). 

slumping and erosion. 

9 Ludwig's 

The southern end of the island shows extensive 

Offshore the bottom is composed mainly of large, rounded, eroded 

boulders covered with a low algal turf. Farther offshore in deeper water 

the bottom becomes pavement like. At individual and isolated areas 

patches of sand and gravel are found. 

Other descriptions of the island are also contradictory. Corte 

(1875) stated that it has an elevation of about 610 m (2,000 ft). Fritz 

(1902) indicated that the height of the southern half was 50-60 m 

(164-197 ft) and that the northern half was lower. Corte (1875) also 

indicated that there was a brackish water lagoon large enough for boats 

to enter along the western shore. Fritz (1902) described a crater at the 

west which had "fallen in." Additionally, there is confusion concerning 

Ibanez y Garcia's (1886) and Corte's (1875) description of an island 

later named Farallon de Torres, which was about 30 km (16 mi) south of 

Guguan. Fritz (1902) considered that Ibanez's description of the two 

islands to be an error. 

Intertidal and shallow ater animals were collected during January -Y and July 1975 and July 1981. 

observed. Numerous coral and associated crustaceans and gastropods were 

A wide variety of echinoderms were 
17 

also observed. A number of herbivorous fishes were present. 

Baker (1951) reported the known birds. Eldredge (1975) estimated 

that there were more than 50,000 sooty terns along the slopes of the 

northern volcano. 

observed throughout the archipelago. Boobies, tropic birds, frigate 

birds, and noddy terns were abundant. 

This island has the greatest number of seabirds 

Coconut crabs and other land crabs were abundant. Ronck (1975) 

Bats were relatively 

Small rats were 

A total of 57 species of 

reported on the "zoo-sized assortment of birds." 

common and could be seen most times during the day. 

common in the interior of the southern part. 

vascular plants have been reported (Fosberg et 81. 1975, 1977). 

ALAMAGAN 

This steep-sloped island is located at lat. 17'35" and long, 145" 

51'E (Figure 18). Its elevation is 744 m (2,441 ft) and area is 11.2 sq. 

km (4.7 sq. mi). The island has been previously known as Alamagan Insel, 

Alamguan, Almagan, Alemagen, Alimagan, Aramagon To, Artemagan, Artomagan, 

Ile de la Conception, La Conception, Ora-Magan, and Uramagan (Bryan 

1971). 

The only recorded volcanic activity for Alamagan is a minor event in 

the 1860s and a lav 

mittently observed. Fritz (1902) reported "warm springs of fresh water" 

in the northern part of the island. 

and ash eruption in 1885, although fumes are inter- 3 

The coastal area is very irregular and consists mainly of low headlands and steep cliffs. A large 

boulder and cobble shore, located near the village along the southwest 

coast, is the only place to land at the south. 

shores are unknown. 

large erosion scars, exposing light-colored basalt material (Figure 19). 

There are no small-grain sand beaches. 

Features of the remaining 

The southern end of the island is marked by very 

Offshore at the anchorage the substrate looks like a fringing reef 

limestone platform which is covered with a low growth of algae. 

Acanthaster planci were observed, as well as several sea cucumbers. 

Large 

A total of 178 species of vascular plants are known (Fosberg et al., 

1975), and birds are recorded (Baker 1951). Fritz (1902), Yawata (1940), 

and Ludwig3 mentioned several archaeological sites. I_ 

PAGAN 

Pagan is the largest and the most complex island among the northern 

The maximum elevation is 569.9 m (1,870 ft) at the southern 

group. It is located at lat. 18°03'-18010'N and long. 145°43'-145049'E 

(Figure 20). 

end of the island and the area totals 47.7 sq. km (18.5 sq. mi). The 

island has been previously known as Agan, Ile de Saint Ignace, Pagan 

Insel, Pagan To, Pagaon, Pagara, Pagon, Papan, Paygan, Pegan, Pegon, 

Pragan, Praien, Prajan, Pemplie de Volcans, Remplie de Volcaus, San 

Ignace, and Saint Ignace (Bryan 1971). 
18 

The island has an extensive history of vulcanism. Explosive eruption took place between 1820 to 1830 and during the last half of the 19th 

century. Marche (1890) reported a violent eruption occuring around 1870. 

Since 1900, eruptions have been reported in 1909, 1917, 1923, and 1925 

(Tanakadate 1940). 

the west from Mt. Pagan in 1925. 

described in detail in Corwin et al. (1957). 

Ash was ejected during the last two; lava flowed to 

The island's geophysical history is 

On May 15, 1981, Mt. Pagan erupted violently, depositing more than 

90 million cubic meters (118 million cubic yd) of ash and other volcanic 

material by May 28. 

flowed to the north, south (Figure 21), and west to depths of 3 to 30 

meters (9.8 to 98.4 ft). 

in) in some areas toward the northwest (Banks 1981). A team of U.S. 

Geological Survey scientists visited Pagan immediately following tke 

eruption and collected samples which are presently being examined. 

[The impact of the eruptions will be discussed later.] 

Lava, originating at three newly formed vents, 

Ash and scoria settled as deep as 200 cm (78.7 

Pagan's 43.4 km (27 mi) coastline is diverse. Most of it is composed of near-vertical headlands and steep slopes. Truncated volcanic 

platforms are found along the west coast. Beaches, varying in length 

from 50 m to 1000 m (164 to 3,280 ft), are scattered among low headlands. 

Most beaches are composed of cobble-sized material. Beaches composed of 

fine-sized material are found only along the west and southwest shore of 

the northern half of the island. All the southern beaches consist of 

large, coarse material. 

Raised reef limestone and limestone conglomerate shores are found in 

restricted areas at the north (Talagi), along the east (from Regusa to 

Apansantate and at Inai Dikiki), and at the west (Liyan). They are uplifted as much as 1 m (3.3 ft) and the surface is pitted. Surge channels 

are elevated and blow holes are common. These are the only raised limestone shores in the northern islands. Most of these shores have a mixed 

limestone-volcanic sand beach landward. Cobble beaches with mixed limestoneare found scattered around the island (Corwin et al. 1957). 

More recently, 19 beaches on Pagan were investigated (Doan and 

Siegrist 1979) for their suitability as a source of fine aggregate. 

composition, texture, and size variation of the beach material and the 

dimensions of the beach are presented along with expected inshore surf 

conditions. 

The 

In general terms Corwin et al. (1957) described the offshore environmental condition as: 

Class I. At more'recent lava flows the coastal shelves are very 

narrow and have rough, rocky bottoms. In some areas there is 

no shelf, in others it may extend seaward as much as 450 m 

(1,476 ft). 

blocks, and cobbles. Sand patches are widely scattered. 

Most of the bottom is composed of lava, lava 

Class 11. These moderately wide shelves with corals and algal 

growth are found around much of the northern half of th island. 

Class 111. Along the isthmus, at the southern end, and at the 
19 

northeastern side of the island these wide to very wide shelves 

gently slope seaward. 

algae are found. 

The bottom is rough rock and coral and 

Class IV. This very wide shelf area is found only along the western 

shore from Bandera to Puntan Laguna. It is characterized by 

having a moderate slope and a smooth volcanic bottom. 

outer edge is about 1400 m (0.7 mi) offshore at adepthof 183 m 

(100 fathoms). 

shore is composed of large boulders, low headlands, or sandy 

beaches. 

zone both intertidally and subtidally. 

boulders are eroded and wave washed. 

low headlands with nearly vertical walls rise off the bottom 

from about 2 m (6.5 ft). Further offshore blevated and 

isolated boulders are the bases for coral colonies. Toward the 

southern end much of the shoreline is high, steep cliffs and, 

in places, low, narrow shore is composed mainly of rounded 

volcanic boulders. Large ones are found at the water's edge, 

and a mixture of sizes, subtidally. 

The 

More superficially, much of the accessible 

The dock site at Bandera is an example of a boulder 

Cobble-sized volcanic 

To the north at Katchu, 

Two lakes are found at Pagan. They are thought 80 be quite young 

geologically, having been formed about 200 years ago. Before the recent 

volcanic eruption the inner lake (Lagunan Sanhalom) had a length 

("E-SSW) of 560 m (1,840 ft), a width (E-W) of 525 m (1,720 ft), average 

depth of 15 m (50 ft), and an area of 0.174 sq. km (43 acres). The outer 

lake (Lagunan Sanhiyong) (Figure 21) had a length (N-S) of 759 m (2,640 

ft), width (E-W) of 310 m (1,020 ft), an average depth of 12 m (40 ft), end 

an area of 0,160 sq. km (39.5 acres) (Corwin et al. 1957). Following the 

volcanic eruption the shoreline of the inner lake was reduced by about 2 

m on all sides. 

near the inner lake. 

filled with volcanic material, but the water along that shore has 

remained very warm. 

BetEeen 12 and 40 cm of ash and scoria were measured 

The hot springs along the southeast shore were 

Corals are abundant in the shallow-water areas. True coral reef 

development is limited--reefs may be found at Salafai along the southwest 

shore and at Apansantate along the southwestern shore. 

communities occur around most of the island wher ver there is stable 

substrate. During a trip in March 1981, Randall collected 

representatives of 111 species belonging to 37 genera. 

Extensive coral 

7 

*" 

During survey trips in 1975 and March and July 1981, several hundred 

gastropod and crustacean specimens were collected and are currently being 

examined. The marine algae are known $<;;I;;'previous records (Tsuda and 

Tobias 1977a, 1977b), and additional material is also being 

investigated. 

observed in the field during a March 1981 visit. 

Approximately 200 species of fishes were collected or 

On land more than 200 species of vascular plants have been reported 

(Fosberg et al. 1975, 1977, 1980). Additional species were recorded 

during the March and July 1981 survey. 

birds. Monitor lizards are common, and bats occur throughout the island. 

Baker (1951) reported on the 
20 

A note should be added about the effects of the May 1981 eruption on 

the island. Five biologists from the University of Guam visited Pagan in 

July 1981. 

Leaves of trees were shed or damaged by the ash and scoria fall. After 

the eruption every species of plant seen previously were found somewhere 

on the island. Toward the southern end, the vegetation appeared 

unaffected. The lakes appeared quite similar, chemically, to that found 

before. Shoreline, intertidal, and shallow-water habitats were severely 

disturbed (Eldredge 1982). Where surf has altered the scoria, original 

physical conditions are returning. At the north end at Talagi more than 

200 cm (78.7 in) of scoria covered the shoreline and low headlands, as 

well as filled a large blowhole. The intertidal gastropods found 

previously along the shore were totally absent or very much reduced in 

numbers. 

material. 

been cut off from water circulation by a low volcanic berm. Gastropod 

and algal zonation observed in March was seriously altered by floating 

scoria and pumice. Subtidally, low encrusting corals were smothered, and 

upright branching forms were heavily damaged. At Kachu 94 colonies were 

counted. Of these 38 (40%) were alive, 41 (44%) were dead, and 15 (16%) 

were heavily damaged. At the bay south of Bandera, of 59 coral 

The lava flows obliterated all vegetation in their paths. 

The white-sand beach at Regusa is covered with black volcanic 

The elevated spurs and grooves are filled with scoria and have 

(Pocillopora elegans) colonies, 27 (46%) were alive, 8 (13%) were dead, 

and 24 (41%) were heavily damaged. 

AGRIHAN 

With the highest elevation in the Marianas, Agrihan is located at 

lat. 18"46'N and long. 145'40'E (Figure 22) and has an elevation of 965 m 

(3,166 ft). The land area is 44 sq. km (18.3 sq. mi). The island has 

been previously known as A-Grega, Agrega, Agrigan, Agrigarn, Agriguan, 

Agrijan, Agrijon, Aguijan, Ajujan, Agurigan To, Agurijan, Ergua, Gilen, 

Greca, Gregua, Greguna, Greje, Griga, Grigan, Guanan, Guerga, Ile de 

Sainte Francois Xavier, San Francisco Javier, and Volcan de Griga (Bryan 

1971). 

Although relatively inactive, Agrihan's volcano erupted ash in 1917 

(Hasegawa 1917; Tanakadate 1940). More recently Stern (1978) provided an 

in-depth review of the geology of Agrihan. He noted three 

geomorphological provinces--shoreline, slopes, and central caldera--and 

detailed the stratigraphy and petrography. 

Elevated cliffs and steep slopes characterize the coastline. 

Pebble-sized black sand beaches are found only along the southwestern 

shore (Figure 23). These are as wide as 30 m (98.4 ft) and may have a 

high seaward berm during s asons of heavy surf. 

during the summer of 1978, 

A berm was present 5 

as well as during a January 1975 visit.4 

Very little is known about the biota. A single dive was conducted 

north of a low headland along the west coast. The shore was rough, 

irregular lava broken into blocks which gently sloped to deeper water 

where the bottom was a smooth, eroded, polygon-like pavement. Few 

animals, other than limpets, were observed in the intertidal zone. 

Occasional heads of Pocillopora were present on slightly elevated blocks 

and boulders. A low encrusting form of Eire coral (Millepora) - was 
21 

predominant, and the sea urchin Diadema setosum was common. The asteroid 

Linckia multifora was found in great numbers and were unusual because of 

their large size and because many were found in various stages of 

regeneration. 

On land, nearly 150 vascular plant species have been recorded 

(Fosberg et al. 1975). The birds are listed by Baker (1951), although 

Borror (1947) specifically discussed those of Agrihan. Jouanln (1959) 

added the record of a nesting colony of black-footed albatross reported 

at Agrihan in 1888. 

ASUNCION 

The nearly perfect cone of Asuncion is located at lat. 19"40'N and 

long. 145"24'E (Figure 24). The island has been previously known as 

Asomson, Asoncon, Asoncun, Asongsong, Asonson, Assomption, Assongsong, 

Insel, Assongsong Is. , Assongsong, Assonguson To, Assumption, Asumcion, 

Asumpcion, Asuncion, Chemecho, Chemecoa, Cherpshn, Cheroshuns, Ile de 

l'Assomption, Insel de l'Assomption, Isle de Volcan, Las Mojas, Semoguan, 

Sonsong, Volcan Grande, Volcano Grande, and Volcgrande (Bryan 1971). 

The island, which has an elevation of 891 m (2,923 ft) and an area 

of 7.3 sq. km (2.8 sq. mi), has had a somewhat quiet geological history 

during bistoric times. 

flowed, 

slope (Figure 25). Minor eruptive activity occurred .during the early 

1920s but none is known since, althotgh the volcano is still active as 

evidenced by intertidal hot springs. 

During an explosive eruption in 1906, lava 

forming the distinctive inverted chevron halfway down the west 

The shoreline is composed mainly of low to high steep cliffs and 

isolated truncated basaltic platforms and associated pools. 

end along the southeastern shore. 

northeast coast shows extensive erosion. A shore of large, oval 

cobble-sized boulders is found along the west coast. No sand-grain-sized 

beaches were observed. 

These pools 

Much of the shore along the east and 

A small hot spring was found along the west coast near a wide 

basaltic platform. 

temperature and salinity measurements wexe recorded seaward from the 

spring during a low tide (July 8, 1975): 

Along a landward-seaward line the following 

Temperature ("C) 

39 + 

39 + 

31.8' 

Salinity (" / O O ) 

8.884 

7.774 

31.085 

The ambient seawater temperature was 20.8"C and salinity was 34.42"/,, 

At high tide when the pools were filled, the salinity was the same as 

ambient (34.44"/,,), and the temperature ranged from a high 

amb ien t . of 32°C to 
22 

Little is known of the marine biota. In the deeper water the coral 

community is relatively rich. Several gastropods have been collected. 

In the intertidal zone the major animals are abalone (Haliotis sp.), as 

abundant as 4 per sq. my and sea urchins (Colobocentrotus mertensi). 

Fritz (1902) visited the island and noted that the plants of earlier 

settlers had "gone wild" and were widely spread. 

species are now known from Asuncion (Fosberg et al. 1975, 1977). There 

appears to be a relatively distinct vertical distribution of vegetation 

forms. Coconuts, pandanus, and hibiscus form a zone from above the 

strand or wave-washed areas to about 100 m (328 ft). Above this, a zone 

of swordgrass continues upward, becoming sparse, until volcanic material 

is the major cover. 

the east side of the island. 

A total of 70 plant 

Swordgrass is the major vegetational form throughout 

Fritz (1902) related an interesting story about the possibility of 

English treasure being buried at Asuncion. He briefly told of a Spanish 

governor's unsuccessful search for the treasure and the realization that 

the treasure might be at Pagan. 

MUG 

Three islets comprise the island of Maug which is located at lat. 

20"Ol'N and long. 145" 13'E (Figure 26). The island has been previously 

known as Bato, Buvi, Eunas I., Las Monjas, Les Isles Uracas, Madug, 

Mahao, Manao, Mang, Mangs, Mao, Mauga, Maui, Mauo, Mayug, Mogu To, 

Monjas, Moug, Mougu To, Ota, Ota-Mao, Sainte Laurent, San Lorenzo, Tina, 

Tuna, Tunas I., Urac, Uraccas, Urakas Is., Urracas, and Urracus (Bryan 

1971). 

The three islets are North Island (=Kita Shima) with an elevation of 

227 m (746 ft); East Island (=Higashi shima) with an elevation of 215 m 

(709 ft); and West: Island (=Nishi shima) with an elevation of 178 m (591 

ft (Figure 27) 

Notes on the island's geology were first made by Fritz (1902) who 

described the geology and vegetation in very general terms. 

on the basaltic dikes. Under the League of Nation's mandate, a number of 

Japanese scientists visited the islands beginning in 1922. Tayama (1936) 

considered all three islets as being originally part of a single volcano 

called Maug Volcano. Following a brief visit, Tanakadate (1940) 

discussed the form of the volcano and the composition of the material. 

It is conjectured that the present form of Maug resulted from a massive 

and explosive eruption. 

He remarked 

A weather station was established at the summit of East Island in 

1939, and a small fish processing plant was once located at the west 

shore at East Island (Eldredge et al. 1977). Remnants of the concrete 

work at both places presently remain. 

The shoreline is irregular. On the ocean side of the island most of 

the shore is either consolidated headland or composed of small eroded 

materials. At the water level the coastline is either vertical or 

undercut. The islands form steep slopes between 45" and 60'. Rough 
23 

water generally makes access to the ocean side hazardous. 

side the islets are almost vertical in slope, although narrow areas allow 

access to the heights. 

along the north end of East Island. Vertical basalt dikes with 

intermittent stratified unconsolidated material are major visual features 

of North and West Islands. East Island is the highest; West Island has a 

very irregular outline. 

On the lagoon 

The remnants of a masonary trail can be seen 

Most of the shoreline is composed of large rounded boulders or low, 

consolidated headlands. 

East Island. A man-made bulkhead is located near the north end and a 

low, truncated offshore basaltic mound is situated off the north end of 

East Island, 

unconsolidated cobble-sized boulders is located at the west end of North 

Island. 

A few scattered "beaches" are at the bases of 

At the north tip of this island the shore is composed of 

Toward the center of the lagoon, most of the substrate is 

consolidated basaltic boulders veneered with scattered broken boulders, 

presumably resulting from terrestrial erosion. A narrow, smooth 

limestone terrace is found along the east side of West Island. 

extends from shore 5 to 10 m (16.4 to 32.8 ft), gradually slopes to a 

depth of 25 m (82 ft) and then drops out of sight. 

along the north end of East Island is covered with a mixed 

basaltic-and-bioclastic sand. 

narrow and becomes very deep close to shore. 

North Island depths of 64 to 90 m (35 to 49 fathoms),are found. 

This 

The shallow terrace 

Throughout the lagoon the terrace is 

Along the south shore of 

The entire lagoon has been swept to a depth of 15 m (49 ft). The 

northwest entry channels has been swept to depths of 4.6 m (15 ft). 

During the November 1977 natural history survey, a Japanese trolling boat 

passed through this channel and exited through the south passage. 

The biota of Maug is among the better known of the northern islands. 

A natural history survey was carried out during November 1977 (Eldredge 

et al. 1977). 

Seventy-four species of scleractinian and four of nonscleractinian 

corals have been reported. 

total number of coral species. 

the eastern shore of West Island where the terrace is as wide as 50 m 

This probably represents only a portion of -&Z 

The most diverse area was midway along 

(164.0 ft). 

dominated the inshore area. 

Here large ramose-columnar colonies of Acropora irregularis *- Further offshore Millepora platyphylla, 

Porites lutea, and Goniastrea sp. were predominant. A narrow, well 

developed fringing reef was observed at the seaward side along the 

southern end of West Island where coral coverage was high and species 

composition diverse. 

formed. 

coral community. 

Within the lagoon no reefs are being actively 

In general, the coral development should be considered that of a 

Characteristically, the algal communities are predominantly 

low-lying, turflike forms which are fed upon by a great number of 

herbivorous fishes. 

known from Maug (Tsuda &idTobias 1977a, 1977b, Eldredge et al. 1977). 

The collection of Laurencia succisa represents a new record for 

A total of 60 species of benthic algae are currently 
24 

Micronesia, and Homeostrichus flabellatus, known previously in Micronesia 

from dredged specimens from Guam, was abundant along the lagoon side of 

East Island. 

A wide variety of marine invertebrates is known from Maug. Two 

species of abalone commonly occur. The sea urchin [Colobocentrotus 

mertensi) is the most abundant intertidal invertebrate and may have an 

abundance as great as 26 individuals perlpuarter meter square. 

species of gastropds have been recorded. 

species, 4 soft coral species, and a black coral (Cirripathes sp.) are 

a19 o known. 

Eight-six 

Twenty-one echinoderm 

The greatest fish abundance and diversity were found along the reef 

communities at the north end of East Island and the central part of West 

Island. 

all the habitats examined. 

seaward side of West Island were not found within any of the lagoon 

observations. 

survey, as well as during the Commonwealth 1978 survey. 

species of fishes have been reported as a result of five different and 

separate examinations. 

The most abundant fishes were kyphosids and acanthurids within 

Two species of pomacentrids found on the 

Sharks were relatively abundant during the November 1977 

A total of 232 

Some terrestrial observations have been made at Maug (Eldredge et 

al. 1977). The plants have been listed (Fosberg et al. 1975, 1977) and 

further vegetation patterns have been noted (Eldredge et al. 1977). In 

general, low growing grasses, sedges, and vines (Iponioea, Wollastonia, 

Cyperus , Capparis) cover the slopes. 

Hibiscus) form distinctive groves. Pandanus tectorius is present, and 

large stands of Crinum are present on East and North Islands. 

wood (Casuarina) and coconut (Cocos nucifera) are found only at the top 

and on the outer slopes of East Island. A total of 59 terrestrial vascular plants are known. 

Larger trees (Terminxia , Pisonia, 

The 1rn:iA few specimens of a widespread terrestrial snail (Succinea sp.) 

were collected at an elevation of 60 m (197 ft) on East Island. Juvenile 

earthworms (Dichogaster sp.) were collacted from among leaf litter. 

Sixteen species of birds are reported from Maug. Yamashina (1940) 

made the first bird sightings. The major report is that of Baker (1951) 

who studied all the bird fauna. Falanruw (1975) reported the megapods, 

and Owen (1977) prepared a checklist of the birds. 

Fruit bats (Pteropus mariannus) were observed in November 1977, as 

were several species of skinks. Small rats w re seen in an abandoned 

cistern and around the weather station ruins, 

facility. Maug is now protected as an island to be "maintained as uninhabited place[s] and used only for the preservation of bird, fish, wildlife, and plant species" by the Constitution of the Commonwealth of the 

Northern Mariana Islands (Article XIV, Natural Resources), marine 

resources (Section 1) and uninhabited islands (Section 2). 

'5 

The island has been considered as a site for an oil-transshipment 

URACAS or FARALLON DE PAJAROS 

This round island is covered with recent lava except for two promon- 
25 

tories along the southern shore. 

about 60 m (197 ft) (Figure 28). The island is located at lat. 20'32" 

and long. 144'54'E. Its elevation is 334 m (1,047 ft), and its area is 

2.04 sq. km (0.79 sq. mi). The island has been previously known as Ana, 

Desieria, Farallon and Poraro, Farallon de Pajajos, Farallon de Pajaros, 

Guaban, Guy Rock, La Ingelesa, Pajaros, Poraro, Rocher de Guy, Urac, 

Uracas Insel, Urakas, Urakasu To, Uricas, Urracas y Farallon de Pajaros, 

and Vogelinsel (Bryan 1971). 

One promontory has an elevation of 

Little vegetation is present on the volcano slopes except on these 

The first reported minor 

raised promontories which remain from pre-1900 eruptions (Figure 29). 

Records of eruptions are not well documented. 

eruption was in the mid-1860s; the first with lava flows in the late 

1870s. 

since the 1900~.~ 

island reported changed by violent volcanic eruption (1943)." Between 

1975 and 1978 an eruption formed a major hydrothermal vent along the 

northeastern "&re which is emitting a colored-water plume rich 

an ash eruption apparently occurred during 1977-78, since fresh ash 

showed little evidence of rain erosion and was present along the shore 

headlands, having been unaffected by seasonal rain or high surf. A 

different 

Steaming and minor eruptions have been noted almost continuously 

On DMA Chart No. 81086 a note reads, "Profile of 

n iron 

and manganese. This same plume was observed in mid-July 1981. 6 Also 

colored plume was observed in July 1975 along the west shore. 

The shoreline consists primarily of eroded lava blocks and low 

cliffs. 

disappear with volcanic activity. Only a few intertidal organisms are 

present--1ittorines (L. pintado), limpets (Cellana sp.), grapsid crabs 

(Grapsus tenuicrustatus) , and sea urchins (Colobocentrotus mertensi)-- 

along with some filamentous algae. These probably represent the first 

stage of recolonization of the newly deposited shoreline. In deeper 

water bare boulders and isolated sand patches form the substrate for 

scattered coral growth. Several species of fish, including many moray 

eels, were observed. On the more elevated boulders coral growth was 

richer, and a few gastropods were collected. 

Small, narrow "beaches" occur in isolated areas and probably 

On land about 11 species of plants have been reported (Fosbetg et 

al. 1975). Seven species of seabirds were observed in July 1975, and 

the megapod has recently been reported (Falanruw 1975). 

BANKS 

Zealandia Bank, located at lat. 16O53'N and long. 145°51'E, is a low 

exposed bank of different reported heights. Fritz (1902) indicated that 

the Bank was about 2 m (6.6 ft) high; Lehne and Gabler (1972) reported 

0.6 m (2 ft). 

(1964) provided information that the bank "consists of two rocks, that 

dry about 0.6 m (2 ft) and lie about 0.8 km (0.5 mile) apart, northeast 

and southwest" (p. 389). During April 1983 Zealandia Bank was visited by 

University of Guam researchers. A short dive 

at the more northern one showed that it was straight sided and rose from 

a flat-topped platform about 30 m (100 ft) in depth. 

(1972) also referred to this area as Papaungan.] 

*- 

The "Sailing Directions for Pacific Islands" volume I 

Two exposures were noted. 

[Lehne and Gabler 
26 

Supply Reef, located at approximately lat. 20'10'N and long. 145"04' 

E, is circular in outline. The "Sailing Directions for Pacific Islands" 

(1964) reported the reef as "having a least depth of 4-1/2 fathoms on its 

south. It is marked by discolored water and by breaking seas" (p. 392). 

Corwin provided a sketch of Supply Reef adapted from that of Tayama 

(1936). Coarse ash covers the north half of the entire cone. 

5 

Galvez Bank and Santa Rosa Reef, banks west of Rota and Saipan and 

north of Farallon de Medinilla, "Bank A," and Arakane Reef have recently 

been mapped and figured (Polovina and Roush 1982). 
27 

CLIMATE 

The climate of the Mariana Archipelago is uniformly warm and humid 

throughout the year and can be considered tropical toward the south and 

somewhat subtropical toward the north. The annual variation of mean 

monthly tenlperatures range from 2°C (3°F) at Guam to 3°C (5°F) at Pagan 

(Corwin et al. 1957). There are two well defined seasons--a dry season 

extends from January through May, and a wet season from July through 

November. [Corwin et al. (1957) stated that the dry season at Pagan was 

from November to June and the wet season from July to October.] The remaining months are considered transitional and may be either wet or dry 

depending upon the overall periodic cycle. 

The most extensive climatic review for Guam is that of Blumenstock 

A short updated 

An overall description 

(1959) and for Pagan, that of Corwin et al. (1157). 

review for Guam is that of Eldredge and Kropp. 

of western Pacific weather was prepared by the U.S. Weather Bureau 

(1943). 

the National Climatic Center of the Environmental Data and Information 

Service. Additional information is available from the National Oceanography Command Detachment (formerly Fleet Weather Central/Joint Typhoon 

Warning Center) at Guam and from the Naval Environmental Prediction 

Research Facility at Monterey, California. Predicted astronomical data 

for 1983 has been prepared by the Naval Oceanography Command Detachment 

(1982). 

"Local Climatological Data" is compiled continuously at Guam by 

Air Temperature 

The temperature at sea averages 27" to 29°C (80" to 84°F) with a 

monthly variation of 1°C (2°F) (U.S. Weather Bureau 1943). Between lat. 

10" and 20"N this variation may increase 2°C (4°F). 

the air temperature at lat. 10"-15"N and long. 140"-145"E is 27OC (80°F) 

and at lat. 15"-20"N and long. 140"-145"E, 28°C (81°F), as calculated 

from the U.S. Weather Bureau (1943),averaged for the years between 1881 

and 1933. -North of lat. 25"N, a wide range of temperatures prevail, 

More specifically, 

Temperature on land also varies little. At Guam the coolest months 

are January, February, and March and the warmest are May and June. 

range between the coolest and warmest months is slightly less than 2'C 

(3°F). 

ture recorded between 1941 and 1980 was 35°C (95°F) in September 1957, 

although Blumenstock (1959) reported an earlier temperature of 38°C 

(100OF). 

the Weather Bureau Building at an elevation of 120 m (361 ft). 

ture data for Guam are presented in Table 1. 

The 

m- The differences between the monthly minimum and maximum temperaThe lowest temperature was 12°C (54"F), recorded in March 1965 at 

TemperaAt Pagan, Corwin et al. (1957) noted that the observed maximum 

temperatures were more variable than the minimum temperatures. 

July, August, and September the observed temperatures ranged between 

26.6"C (79.8"F) and 36.4"C (97.6"F), the mean being 31.8"C (89.2"F). 

During 
28 

Humidity __ 

The relative humidity is high throughout the year. At Guam the 

rei-ative humidity averages 77 percent at 1600, 90 percent at 2200, and 92 

percent at 0400 (Table 2). 

humidity drop to less than 60 percent. Humidity lower than 40 percent 

has never been observed (Blumenstock 1959). 

Extremes do occur but rarely does the 

At Saipan 6-year measurements showed a relative humidity of 88 

percent at 0600 and 74 percent at 1400 (Meteorological Office 1975). 

The mean relative humidity at Pagan was 83 percent, resulting from 67 

observations made during the summer of 1954 (Corwin et al. 1957). At 

1400 the average minimum humidity was 74 percent, and the average maximum 

was 87 percent in the early morning between midnight and 0600. 

The decrease in relative humidity between Guam and Pagan should be 

noted as indicative of a less tropical climate toward the north. 

- Wind 

The entire western Pacific area is dominated by the east and northeast tradewinds. In the western part, west of long. 140"E, monsoonal 

winds develop. Here at sea there is a shift from northerly winds during 

the winter to southerly winds during the summer (U.S. Weather Bureau 

1943). The annual mean surface wind velocity is shown in Figure 30. 

average surface wind drift direction, constancy, and.force is shown in 

Figure 31. 

The 

In the ocean area around the Mariana Archipelago, the northeast 

tradewinds predominate during most of the year except during the summer 

months. These winds are present in about 35 percent of the observations 

annually near the equator (U.S. Weather Bureau 1943). During the winter 

occasional north, northwest, and west winds may be observed, and during 

the summer southeast tradewinds may occur. Further north between lat. 

20" and 25"N, northeast and east winds occur about 47 percent of the 

time . 

Specifically for the area between long. 140" and 145"E (U.S. Weather 

Bureau 1943) the average sea wind velocities near the equator are light 

and show little seasonal differences. Between lat. 5" and 10"N the 

annual mean velocity south of the archipelago is about 9 knots with 

distinct seasonal differences. During the winter the mean velocity is 

as high as 14.5 knots in February, and during the summer as low as 4.9 

knots in August. For lat. 10" to 15"N, the mean velocity is 9.4 knots. 

The high mean is 13 knots for January, and the low is 8.4 knots for July 

and August, showing less extremes than to the south. For lat. 15" to 

20"N the mean velocity is 10.1 knots. Speeds of more than 10 knots are 

found during eight months. 

during June. 

knots. 

The lowest speed of 7.6 knots was recorded 

North of lat. 20"N the mean velocity decreased to 9.6 

West of the Marianas the speeds range from 10 to 15 knots monthly 

The summer monsoon affects a wide seaward area, 

from October to March and 8 to 11 knots from April to September (U.S. 

Weather Bureau 1943). 

and the winds are lighter eastward through the Marianas. 
29 

On the islands during the dry season a more northerly element occurs 

and the winds blow as much as 90 percent of the time. Characteristics of 

winds at Guam are shown in Table 3, 

and afternoon, and lightest winds, at night (Eldredge and Kropp ). Other 

seasonal differences also occur. 

season and may be interrupted by tropical cyclonic disturbances (Figure 

32). 

Highest winds occur in late morning 

The tradewinds weaken during the wet 

The percentage frequency of wind direction by speed and hour for 

Guam, Saipan, and Pagan is shown in Tables 4, 5, and 6, respectively. 

Rainfall 

Rainfall varies markedly geographically and seasonally. Rainfall 

increases at Guam between July and November during the wet season when 

more than 60 percent of the annual rain fall. Rain falls on about 75 

percent of the days. The average monthly rainfall is about 357 rmn (14 

in) during August, September, and October; however, more than 569 mm (26 

in) were recorded in October 1979. Tropical cyclones occur during the 

wet season. During the dry season--January through May--as much as 20 

percent of the annual rain may fall. Generally less than 54 mm (5 in) 

has been recorded for each month. Even though tropical cyclones are rare 

during the dry season, Typhoon Pamela passed directly over Guam in May 

1976 and dropped 686 mm (27 in) of rain, the highest 24-hour rainfall on 

record, The average annual rainfall is 2286 mm (90.6 in) (EDIS 1981); 

however, generally the rainfall is somewhat greater in the mountainous 

southern half with 2794 mm (110 in). 

maximum and minimum monthly rainfall, and mean number of days of rainfall 

are presented in Table 7. 

Normal monthly rainfall averages, 

A 19-year average rainfall at Saipan was 2080 mm (82.2 in) (Meteorological Office 1975). 

rainfall was probably 1776-2030 mm (70-80 in) because of the differences 

in relation to the convergence zone. 

indication of the less tropical climate toward the north. 

At Pagan Corwin et al, (1957) stated that the 

The decrease in rainfall is another 

Storms 

Small-scale storms, mainly squalls and thunderstorms, may periodically dominate isolated areas. At sea thunderstorms occur more often at 

night than during the day (U.S. Weather Bureau 1943). 

create conditions for thunderstorms. At Guam frequency increases during 

the wet season with an average of six in July and seven in August. 

Thunderstorms are rare during the dry season, none having been reported 

during February or March (EDIS 1981). 

have been reported annually (U.S. Weather Bureau 1943). 

the mean annual number of thunderstorm days for the archipelago. 

-. Island land masses 

For Saipan 17 to 18 thunderstorms 

Figure 33 shows 

Squalls and gales occur more commonly during the wet season where 

sudden gusts of winds can cause sudden rainfall. 

squalls can be seen along the horizon. 

winds may bring about sudden winds with gusts to 22 knots. 

percent squall frequencies are found from lat. 15" to 30"N. 

Often several such 

During the dry season the tradeLess than 5 

South of 
30 

lat. 15"N (0"-15'N) these frequencies may be more than 6 percent '(U.S. 

Weather Bureau 1943). 

Gale winds vary and may be associated with cyclones or cyclone generation. They have been reported to occur l to 6 percent of the observations at long. 140" to 145"E between March and September and in November (U.S. Weather Bureau 1943). Two- and 100-year return periods of 

expected extreme wind gusts at Guam (Station 35) arc shown in Figure 34. 

Tropical Cyclones 

Cyclones are counterclockwise wind circulation patterns formed in a I1 central calm core or "eye. The relatively narrow, 74-93 km (46-58 mi) 

in diameter, band of winds and trailing spiral rains cause considerable 

damage when they reach land. 

Cyclone patterns are differentiated by speeds in an internationally 

agreed upon scheme: 

Tropical depression Maximum sustained winds not greater 

than 33 knots; 

Tropical storm Maximum sustained winds between 34 and 

63 knots; 

Typhoon Maximum sustained winds greater than 54 

knots ; 

"Super typhoon" Sustained center winds of 130 knots 

(gusts to 160 knots). 

Because of their high frequency in the western Pacific, 

(Figure 35) tropical cyclones have been examined in detail. 

Climatological statistics--frequency, intensity, movement, and 

environmental conditions--were analyzed by Gray (1970). In particular, 

the effect of cyclones at Guam has been studied by Holliday (1975) and 

Brown and Brand (1975). Gray (1970), using data collected from 1900 to 

1969 with most emphasison those collected between 1946 and 1969, detailed 

the origin, tracks, and positions of cyclonic disturbances, as well as 

trade-wind cloud associations. These disturbances originated over a 

wide area of the western Pacific. The initial locations of tropical 

disturbances which later became typhoons or tropical storms are shown in 

Figure 36. The locations where these disturbances reached typhoon 

intensity are shown in Figure 37. Figure 38 details the initial 

detection locations for June of cyclonic disturbances which later reached 

typhoon or tropical storms or depressions. The heavy solid line 

separates pure tropical cyclones (A) from subtropical cyclones (B). 

About 80-85 percent of all tropical cyclones are A type, the remaining 

15-20 percent are B types and develop generally at latitudes north of 15' 

and 18"N, Subtropical (B) cyclones are formed within the tradewind area 

only during summer and early autumn and are not associated with the 

equatorial trough. Tropical (A) cyclones are formed within a deep 

tropospheric easterly current where vertical and horizontal wind shears 

show peculiar characteristics (Gray 1970). 

The mean annual number of typhoons located in the western Pacific is 
31 

shown in Figure 39. Guam and the Marianas lie southeast of the main area 

of activity (Holliday 1975). 

Typhoons are considered to affect Guam whentheypass within 333 km 

(207 mi) of the island. Nearly 70 percent of those reported between 1948 

and 1975 approached Guam from the southeast (Figure 40) (Holliday 1975). 

The majority of these passed south of a point 111 km (69 mi) north of the 

island. Some (16-22 percent) did not approach from a uniform direction 

but looped or stalled (Figures 41 and 42). 

majority of storms ranged between 7 and 16 knots, averaging 11.5 knots. 

Storms approach more slowly between April and August than between 

November and March. Typhoon Hester (December 1952) passed Guam at a 

speed of 22 knots. 

The forward speed of the 

Winds vary during the passage of typhoons. Maximum sustained wind 

speeds in relation to longitude are shown in Figure 43 and in relation to 

month are shown in Figure 44 from data for the years 1953 to 1968. 

During Typhoon Pamela (May 1976) winds gusted to 145 knots and were 

in excess of 100 knots for six hours (Joint Typhoon Warning Center 1977). 

A speed of 125 knots was reported for Typhoon Karen (November 1962) 

before the Weather Service anemometers failed. The strongest wind on 

record was recorded at Miyako Jima (Ryukyu Islands) at 166 knots during 

Typhoon Cora (September 1966) (Holliday 1975). 

Rainfall is exceedingly variable and depends on.the storm's winds, 

speed of forward motion, and rain gauge location. The greatfest 24-hour 

rainfall recorded was that of 686 mm (27 in) during the passage of 

Typhoon Pamela. Earlier records are Tropical Storm Alice (October 1953) 

with 465 mm (18.3 in), Typhoon Amy (May 1971) with 252 mm (9.'92 in). 

Usually about 102 mm (4 in) of rain is common during the paksage of a 

typhoon. 

Between 1948 and 1975, more than 70 cyclones were tracked within 333 

km (207 mi) of Guam. Only 26 (35 percent) were of typhoon strength at 

their closest (Holliday 1975). The greatest number occur during the wet 

season, October and November having the highest number. Tropical storms 

have been reported during every month (Figure 45). The yearly frequency 

has been irregular since 1954 (Figure 46). 

1976 and Tropical Storm Tip in 1979. An analysis of cyclones near Guam 

indicates that there is a probability of one significant typhoon 

occurring every seven years. November has the greatest frequency of 

storms (Holliday 1975). A high number of cyclones has been tracked for 

that month (Figure 47). 

Typhoon Pamela occurred in 

-. 

For Guam Brown and Brand (1975) evaluated Apra Harbor as a typhoon 

"haven" and discussed its facilities, wind and wave action, storm surge, 

and topographical effects before and after cyclonic activity. Because of 

the lack of wind-breaking topography and because of the harbor's westward 

opening, Apra Harbor was not recommended as a typhoon haven. 

were based on 107 tropical cyclones passing near Guam between 1947 and 

1973. 

Their data 

Unfortunately, no analyses of storm conditions have been conducted 
32 

for any of the other islands in the Marianas. The "Annual Tropical 

Cyclone Report" (formerly Annual Typhoon Report) is compiled by the 

National Oceanography Command Center (Fleet Weather Central/Joint Typhoon 

Warning Center) at Guam. 

wide area of the western Pacific from their origin to their dissipation, 

and a best track of each is also given. During the past several years 

Typhoon Dinah (November 1980) passed over Saipan; Typhoon Carmen (August 

1980) passed near Guguan; Typhoon Faye (September 1978) circled around 

Pagan and Agrihan and moved toward the northwest; Tropical Storm Ivy 

(October 1977) circled around Alamagan and became a typhoon toward the 

northwest; Tropical Storm Carla (May 1974) passed over Saipan, and 95 

percent of the crops were damaged, Pagan and Agrihan reported 45 percent 

damage; Typhoon Ida (September 1972) passed over Pagan; Typhoon Olga 

(October 1972) passed near Asuncion; and Typhoon Faye (October 1971) 

passed north of Saipan. Seidel (1903) noted that a typhoon passed over 

Maug and Uracas on 30 August 1858. Lehne and Gabler (1972) noted 

typhoons at Rota in 1911 and at Pagan and Agrihan in September 1907. 

Holliday (1975) detailed the typhoons occurring between 1671 and 1975 

with special emphasis on those occurring since 1946. 

Each details the cyclones of the year for a 
33 

CHEMICAL OCEANOGRAPHY 

Salinity 

Mean annual surface salinities are shown in Figure 48 (Robinson 

1976). 

in Figures 49-52. 

the Equator and 10"N between two areas of higher salinity. 

the Mariana Archipelago lies within this area of low salinity. 

(1968) showed an increase in salinity toward the north especially during 

the second quarter. This low salinity may have originated in the eastern 

Pacific and moved westward, and it may have been joined with other 

low-salinity water entering through the Mollucca Passage (Cannon 1966). 

More specifically, the quarterly mean salinity at 10 m is shown 

A low-salinity region is noticeable at approximately 

Generally, 

Barkley 

In the northern part of the Mariana Archipelago, deWitt (1972) 

showed that the surface salinity ranged from 34.39"/,0 to 34.94"/,, 

during April and May 1971 (spring Townsend Cromwell cruise), whereas the 

salinity ranged between 34.36"/,, and 34.79"/,0 during November 1981 

(fall Townsend Cromwell cruise) (Figures 53 and 54). Salinity increased 

toward the north during the gpring (deWitt 1972) as Barkley (1968) had 

earlier suggested. 

DeWitt (1972) discussed vertical salinity structure in detail. In 

deeper waters, low salinity water (North Pacific Intermediate Water) was 

present along a layer at the 135 cl/t surface. The depth decreased from 

greater than 550 m (1,804 ft) at lat. 21°N to approximately 40 m (1,312 

ft) at lat. 15"N in the spring, and from approximately 650 m (2,132 ft) 

at lat. 23"N to less than 555 m (1,820 ft) at lat. 17"N in the fall 

(Figures 55 and 56). High salinity water (tropical water) was present 

approximately along the 370 cl/t surface. During the spring the 370 

cl/t surface sloped from less than 100 m (328 ft) at lat. 21"N downward 

to greater than 175 m (574 ft) at lat. 15"N, and during the fall this 

surface sloped from slightly more than 100 m (328 ft) at lat. 23"N to 

approximately 175 m (574 ft) at lat. 17"N (Figures 55 and 56). 

At Guam, the observed salinity and density profiles are typical 

(Figure 57). 

the surface and 35.13"/,, at 150 m (492 ft) (Lassuy 1979). The minimum 

mean salinity occurred at 496 m (1,625 ft). At Tanguisson Point during a 

nine-month sampling period in 1969, surface salinities ranged from 33.83 

to 34.63"/,, with a mean of 34.28"/,, (Jones et al. 1976). A T-S diagram 

has been prepared for the waters off Cabras Island (Figure 58). 

all values are positive, the water in the area is in "stable equilibrium" 

(Lassuy 1979). 

At Cabras Island a salinity of 34.30"/,, was reported from 

*- 

Since 

At Pagan, surface salinity was reported at 33.80"/,, and at a depth 

of 100 m the average salinity was 34.99"/,, (Corwin et al. 1957). 

The mean surface water density at Guam was 25.70 at a mean temperature of 28.5"C for a period between 1949 and 1969. 

was 28.lOl5 at 32°C and the minimum, 19.9a15 at 24°C (U.S. Dept. Commerce 

1970). 

&?e maximum density 
34 

Oxygen 

In a research cruise track approximately 10" west of the Marianas, 

Masuzawa (1967) reported a layer of oxygen with a concentration of less 

than 1.5 ml/l below the thermocline which extended from the coast of 

Japan southward to lat. 3"N. A depth change occurred near lat. 15"N 

(Figure 59). 

At Guam, mean dissolved oxygen and total carbon dioxide measurements 

from the surface at Cabras Island to 905 m (2,970 ft) are given in Figure 

60. In the mixed layer above the thermocline, 0 concentration is high 

and CO relatively Sow. Below the thermocline, 6 production decreases 

rapidly reaching a minimum at about 400-500 m (1,310-1,640 ft). 

maximum CO concentration is reached at about 500-1,000 m (1,640-3,280 

ft) (Lassuy 1979). 

2 The 

2 

Nutrients 

The most detailed and recent information concerning the vertical 

distribution of nutrients in the Marianas is that of Lassuy (1979) for 

Cabras Island, Guam. Nitrate-nitrogen (NO -N), nitrite-nitrogen (NO N), 

and reactive phosphorus (orthophosphate, Pd -P) were measured during an 

annual cycle (February 1978-February 1979) $,om the surface to a depth of 

883 m (2,900 ft). Nitrite-nitrogen was negligible or undetectable at all 

depths. 

measurable amounts and increased with depth (Figure 61). 

2- 

Nitrate-nitrogen and orthophosphate were always present in 

pH and Alkalinity 

Mean values for pH and alkalinity from the surface to 918 m (3,010 

ft) off Cabras Island are shown in Figure 62. The pH minimum closely 

coincides with the CC02 maximum between 800 and 900 m (2,625 and 2,953 

ft) (Lassuy 1979). 
35 

SEA-SURFACE TEMPERATURE 

Sea-surface temperatures vary only slightly throughout the year, 

ranging between 27.2"C and 29.4"C (80.9"F and 84.9"F) (Emery 1962). 

Figures 63-74 show the 15-year monthly mean sea-surface temperature for 

the western Pacific. 

10"-15"N, the maximum temperature observed was slightly more than 34°C 

and the minimum slightly less than 25°C (Figure 75). 

minimum monthly sea-surface charts are provided by LaViolette (1970). 

Temperatures are generally lowest in February and March and highest in 

August and September. 

In an area bounded by long. 140"-145"E and by lat. 

Maximum, mean, and 

In the Marianas, deWitt (1972) reported surface temperatures ranging 

from 27.4 to 29.7"C in April-May and 28.6 to 29.7"C in November (Figures 

76 and 77). 

south. 

During April-May surface temperatures increased toward the 

At Guam, a 10-year period (1963-1972) of surface temperatures taken 

at Tanguisson Point by the Guam Divison of Aquatic and Wildlife Resources 

represents a nearshore seasonal temperature regime (Figure 78). The mean 

temperature during the period was 27.6"C (82"F), the lowest 25.6"C 

(78"F), and the highest 29.4"C (84.1"F). 

the 10 years was 27.4"C to 27.9"C (81.3"F to 82.2"F) (Jones et al. 1976). 

The range of annual means for 

Reef-flat temperatures (29.3"C or 84.7"F) tend to be about 2°C 

(3.6"F) higher than nearshore surface water. 

temperatures may be as high as 33.9OC (93"F), occurring during extended 

low tides (Jones et al. 1976). 

On rare occasions reef-flat 

At Pagan a mean shallow-water tfyperature of 27.40"C was reported 

for a 268-day sample in 1977 (Wyrtki ). 

Thermocline 

As the temperature decreases with depth three distinct temperature 

regions can be noted--a well-mixed surface layer, a thermocline area of 

rapid decrease of temperature, and a deep cold layer. These layers in 

the vicinity of Cabras Island are shown in Figure 79. The mixed surface 

layer generally extends to depths of 90-125 m (300-400 ft) where the 

temperature rapidly begins to decrease. Additionally, summaries of the 

National Oceanographic Data Center (NODC) expendable bathythermograph 

(XBT) data for the Marianas show minimum, maximum, and average 

temperatures from the surface to 760 m. 

-. 

More specifically, at Guam the mean monthly temperatures from the 

surface to 915 m (3,000 ft) are shown in Figure 80. For waters in the 

northern areas of the Marianas, deWitt (1972) detailed temperatures from 

lat. 15" to 21"N along long. 142"E to depths of 1,000 m (Figures 81 and 

82). 

During fishery surveys in 1975, 1976, and 1977 the Japan Marine 

Fishery Resource Research Center (1975, 1976, 1977) carried Out 

temperature profile studies along the Marianas. The results of each of 
36 

three years is shown in Figure 83). 

For a survey of depths to the tops of the thermocline for each 

month, Robinson (1976) mapped the western Pacific on a very broad basis 

(Figures 84 to 95). 
37 

CURRENTS 

Surface Currents 

The major sea-surface current influencing the Mariana Archipelago is 

the North Equatorial Current which flows westward through the islands. 

At Guam the current speeds range from 0.6 knots in December and January 

to 0.2 knots in August. 

97. 

the archipelago. The Subtropical Countercurrent is also associated with 

the northern part of the archipelago. The Kuroshio moves northward 

toward Japan along the Asian coast. 

Circulation patterns are shown in Figures 96 and 

The current moves somewhat to the north along the northern end of 

For the western Pacific the mean direction and force of 

lO-quadrangle surface currents, as well as a current rose showing 

frequency of direction and average drifts within the directions for each 

5" quadrangle,are shown for each month (Figures 98-109). 

More specifically for the Marianas, deWitt (1972) discussed the 

current regimes in relation to 0-, 200-, and 500-decibar surfaces for two 

seasons--spring (April-May, 1971) (Figures 110-112) and fall (November, 

1971) (Figures 113-115). During the spring the surface currents were 

markedly different from the 200- and 500-decibar surfaces. The surface 

shows a narrow eastward flow, whereas the deep waters flowed westward. 

surface eddy (lat. 17"30'N, long. 145"30'E) is not present in deeper 

water; however, all depths indicate an anticyclonic eddy (lat. 19"N, 

long. 143"E) and a westward movement (lat. 17-18", long. 148O30'E) 

(deWitt 1972). 

A 

The westward flow had a speed as great as 30 cm/sec at the surface 

at lat. 21" and 23"N, and a similar southeasterly speed at lat. 17"-18"N, 

long. 142-143"E. 

Subtropical Countercurrent 

Yoshida and Kidokoro (1967) investigated the eastward surface 

current movement between lat. 20" and 25"N which was tentatively 

described as the Subtropical Countercurrent. Additional information 

indicated an eastward flow and confirmation of this was based on monthly 

bathythermograph and reversing thermometer data (Robinson 1969). 

The Subtropical Countercurrent can be traced from long. 122"E to at 

-- 

least long. 160"E and is usually considered to lie between lat. 20" and 

25"N. The current varies with season and location. It has an eastward 

velocity of 0.2 to 1.3 knots with an average speed of 0.5 knots, a width 

of 170 km (100 mi), and a depth of 300 m (Uda and Hasunuma 1969). The 

general location or the Subtropical Countercurrent is shown in Figure 

116. Yoshida and Kidokoro (1967) described the strongest flow between 

January and May, but Robinson (1969) suggested that there was an eastward 

flow during other months also. 

The most detailed survey of this current was that of deWitt (1972). 

During two cruises (spring and fall), he reported a narrow, 100-km (60- 
38 

mi) wide eastward surface flow. 

The eastward flow was greater during the spring; little evidence was 

reported for an eastward flow during the fall. 

Eddies were found during both seasons, 

Nearshore Currents 

Numerous nearshore current surveys have been conducted in many geographically separated locations at Guam, as well as at Tinian (Jones et 

al. 1974) and at Saipan (Doty andlMarsh 1977). 

summarized by Eldredge and Kropp. Huddell et al. (1974) conducted 

surveys during February, March, August, and September 1971 along the 

leeward (west) coast of Guam. 

Guam information has been 
39 

BOTTOM TOPOGRAPHY 

The islands of the Mariana Archipelago comprise the Mariana Ridge 

(Figure 117); Guam, Rota, Tinian, Saipan, and Farallon de Medinilla on 

the frontal arc, the remaining islands on the somewhat parallel active 

arc, the active arc. The bottom topography of the archipelago reflects 

these geologic features (Figure 118). Profiles taken during 1969 show 

the relative bathmetry of the areas as B-C-D on Figures 119 and 120, 

southern islands lie on a common contour of 1000 fathoms (Figure 121). 

More specifically, the depths off Guam increase more rapidly toward the 

west (Figure 122). 

debris, volcanic mud, and Globigerina ooze (Figure 123). 

The 

The deep-sea sediments around Guam show areas of reef 

. 
40 

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46 

MARUYAMA, M. 

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47 

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48 

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49 

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51 

LIST OF FOOTNOTES 

1. Eldredge, L G., and R. K. Kropp. [13811 Guam's ocean. A review of 

the physical, chemical and biological oceanographic literature 

for the waters surrounding Guam. Final draft for Lawrence 

Berkeley Laboratory, Univ. California. 199 p. 

2. SEAN Bull. 7(6):11, 1982. 

3. Ludwig, G. M. (U.S. Fish and Wildlife Science, Honolulu). Island 

summaries prepared following visit to islands in 1978. 

4. Eldredge, L. G. Personnel observations made during January and July 

1975 and July 1981 visits. 

5. Corwin, G. L. (U.S. Geological Survey, Reston, Virginia). Geologic 

maps of the northern Marianas, U.S. Geol. Survey unpublished 

review of Quarternary Marianas volcanoes. 

6. Banks, N. G. (Hawaii Volcano Observatory, Geological Survey, 

Department of Interior). Personal communication. 

7. Randall, R. H. (Marine Laboratory, University of Guam). Personal 

communications. 

8. Myers, R. F. (Marine Laboratory, University of Guam). Personal 

communications. 

9. Raulerson, L. (Department of Biology, University of Guam). 

Personal communications. 

10. Eldredge, L. G. 1981. Preliminary report of environmental survey 

at Pagan following the eruptions of Mt. Pagan. 

11. Vermeij, G. J. (Department of Zoology, University of Maryland). 

Personal communication. 

12. Meijer, A. (Department of Geology, University of Arizona), 

Personal communication. 

13. Wyrtki, K. (Hawaii Institute of Geophysics, University of Hawaii). 

Data on temperature and sea level at Pagan, 1977-1978. 
52 

Table 1. Temperatures (OF), normal and extremes for Guam; highest and 

lowest records for 24 years (EDIS 1981). 

Normal Extremes 

Month max. min . Monthly highest Year lowest Year 

Daily Daily Record Record 

Jan. 

Feb . 

Mar. 

Apr. 

*Y 

Jun . 

Jul. 

Aug . Sep. 

Oct, 

Nov. 

Dec . 

Year 

83.2 

83.3 

84.5 

85.6 

86.4 

86.7 

86.2 

86.1 

85.8 

85.6 

85.4 

84.1 

85.1 

71.5 

71.3 

71.0 

72.5 

73.1 

72.9 

72.6 

72.2 

72.4 

72.3 

73.2 

72.9 

72.3 

77.3 

37.3 

77.7 

79.0 

79.4 

79.8 

9.4 

79. I 

79.1 

78.9 

79.2 

78.5 

78.7 

87 

88 

89 

90 

91 

91 

93 

91 

95 

91 

89 

89 

95 

1978 

1960 

19 65 

1960 

1970 

1975 

1966 

1968 

1957 

1957 

1980 

1866 

1957 

Sep. 

56 

59 

54 

59 

62 

63 

66 

67 

61 

65 

62 

61 

54 

19 78 

1959 

1965 

1965 

1960 

1972 

1959 

1974 

1958 

19 76 

1957 

1980 

1965 

Mar. 
53 

Table 2. Relative humidity (percent) for Guam. The 0400 records are for 

period 1970-1972; 0100, for 13 years; 1600 for 13 years; 2200 

for 12 years (EDIS 1981). 

Re la t ive hitmidit y.( percen t ) 

Hour Hour Hour Hour 

Month 0400 1000 1600 2200 

Jan. 88 77 76 86 

Feb. 88 76 74 86 

Mar. 88 75 74 86 

Apr . 90 74 73 87 

%Y 92 73 73 89 

Jun . 92 76 75 90 

Jul. 94 79 78 93 

Aug . 96 81 80 94 

Sep. 96 81 81 94 

Oct. 95 80 80 93 

Nov . 91 80 81 91 

Dec . 88 78 78 88 

Year 92 78 77 90 
54 

Table 3. Wind 

six years 

direct ion 

characteristics for Guam. 

for 22 years (EDIS 1981). 

Given are mean speed records for , prevailing direction for seven, and fastest speed and 

Mean speed Prevailing Fastest Speed 

Month m.p.h. Direction m.p.h. Direction Year 

Jan. 8.2 E 37 NE 1979 

Feb. 10.2 NE 36 NE 1962 

Mar. 9.0 E 32 NE 1977 

Apr. 8.9 E 64 sw 1963 

bY 8.3 E 76 NE 1976 

Jun . 6.4 E 32 E 19 76 

Jul. 5.1 E 34 E 1963 

Aug. 4.8 E 43 SE 1979 

Sep. 4.7 E 35 E 19 76 

Oct. 6.2 E 44 W 1968 

Nov . 7.8 E 80 NE 1962 

Dec. 9,s E 35 sw 1963 

Year 7.4 E 80 NE 1962 

Nov. 
55 

cl 

Ll 

3 

0 

X 

v 

n 

v) 

U 

0 

C 

Y 

a 

a, 

a, 

a 

v) 

a 

G 

.d 

5 

W 

......... .o . 4~~OuieN400e0 

Ne4 40 

ooqq**o*o N* .. .. 

mmmmr.meNodam ......... .o . 004000000dmw 
56 

*******00 WN .. c.t. 
57 

m r. In 01 m m In m 0 N 0 0 

e m r\i 4 if m PJ 4 o r? \t o 40 

4 

.......... m. 

Nifd 

4ammmrJmmow40 ..... .N. 

N4r-i 40 

c; \d 1; h; .3 N N 4 0 I-1 NO 

OW in o .j r. a VI ow 4 o .... e. 

40 

G<lAsd44dooeo 

Ned 

999999999 O? 

04d*(d*?O Nr? ... . m. 

Nr-wmeWNdo ON '44dddddd w. r.r. 

whmr.mmWm0 om ......... .j. 

~NNGd0000 we 

dN ee 

mwmw~m~oo em......... dwr.WNr(dd0 94 

d *e 

emNmWeNNoGoN 

00d000000dW~ 

......... .r. . 
58 

Table 7. Rainfall characteristics (in inches) for Guam; records are for a 

24-year period (EDIS 1981). 

Rainfall (in inches) 

Mon t h 1 y Monthly 24-hour 

Month Normal maX. Year min . Year max . Year 

Jan 

Feb. 

Mar. 

Apr. 

Jun . 

Jul . 

Aug. 

Sep. 

Oct. 

Nov . 

Dec. 

Year 

5.16 

4.26 

2.94 

4.03 

4.49 

5.19 

9.59 

12.16 

14.08 

14.40 

8.51 

5.85 

90.66 

20.39 

14.79 

16.94 

19.55 

40.13 

11.53 

20.00 

25.66 

24.34 

26.05 

18.14 

16.19 

40.13 

19 76 

1980 

1971 

1963 

1976 

1958 

19 72 

1974 

1980 

19 79 

1957 

1963 

19 76 

fiY 

1.99 

0.67 

0.59 

0.50 

0.90 

1.52 

4.74 

3.87 

6.79 

6.63 

2.08 

2.22 

0.50 

1964 

1960 

1965 

1965 

1959 

1969 

1957 

1965 

1969 ' 

1976 

1973 

1977 

1965 

Apr. 

6.26 1976 

9.24 1980 

3.55 1972 

6.37 1974 

27.00 1976 

4.55 1958 

5.17 1969 

7.81 1971 

7.48 1965 

10.14 1979 

7.26 1957 

6.09 1963 

27.00 1976 
59 

Figure 1.--Index map of the western Pacific Ocean showing the location of Guam 

and the Mariana Islands (Tracey et al. 1964). 
60 

PHILIPPINE SEA 

.' E 

s 0 1 2 3 4 MLES 

Figure 2.--General location map of Guam, showing military reservation boundaries, 

major highways, villages, mountains, and other place names (Randall and Holloman 

1974). 
Figure 3,-&,uminao Barrier Reef and Glass Breakwater at Apra Harbor, Guam. 
62 
Figure 5.--Eastern side of Sasanhaya, Rota,.. 
64 

40' 

05 

15 

55 

145"35, 40' 

Figure 6.--Index map of Tinian. 
65 

Figure 7.--Unai Dankulu, Tinian. 
66 

45' lA 

Figure 8.--Index map of Saipan. 
67 

Figure 9.--1sleta Maigo Fahang (Bird Island), Saipan. 
68 

mi 

aa.5 

22 

43 

rsl 

b2 

I 

Figure 10.--Index map of Parallon de Medinilla. 
69 

Fi cT11re 11 .-.-Surf ac~ disc-oloration at Esmeralda, April 1975 (photo by 

;i r;:> ..- 1.- 
70 

357 

301 

296 

Figure 12.--Index map of Anatahan. 
71 

Figure P3.--AeriaS photograph of Anatahan. 
72 

331 

3b5 

573 

b29 ' I '". 

I 

367 

1. 00. 3% 

c 

*6 - ."=--- 

3 % _____.--------..___. -,-:--_____=-a > 

>>, _I).-- ,.*. 

4- 

. 215 

350 \" 355 

440 

Figure 14.--Index map of Sarigan.. 

549 

4 
73 

-- 

Figure 15. --Sari.gan. 
74 

367 

236 

20 40 ”’ 

,‘ L 

,*‘ ,’ 

_/’ 59 

S __-+ 

_____--- ___--- 

Figure 16.--Index map of Guguan. 
75 

Figure 17.--Aerial photograph of northern end of Guguan. 
76 

379 3Bl 

Figure 18.--Index map of Alamagan. 
Figure 19.--West coast of Alamagan, 
78 

Figure 20.--Index map of Pagan. 
79 

Figure 21..--Aerial photograph of northern Pagan showing the outer lake and 

the caldera rim; dark area in center is lava flow from May-1981 eruptiod 

(U.S. Navy photo), 
619 

Figure 22.--Index map of Agrihan. 
Figure 23.--Village area at southwest comer oi 4grihan. 
199 

e7 , ,/6 MI 

I+ &: 159 

355 'to ! 

i 9' Q.3 

Figure 24.--Index map of Asuncion. 
Figure 2S.--Wesr slope of Asuncion with inverted chevron of lava from 

1906 flow, 
84 

139 i59 

mS 

130 

h.3 

Figure 26. ---Index nap of Elang. 
Figure 27.--Aerial photograph of Maug from the easti 
86 

24 7 229 

T 

NOTE 

Profile of island heporte 

changed by violent volcani\ 

eruption (1943) 

209 

Figure 28.--Index map of Uracas (or Farallon de Pajaros). 
87 

Figure 29.--Profile of Uracas from the west. 
88 
89 

8ymbols shown on charts 3 to 7 

Provniling wlnde tnovb wlth the arrowa 

Dlrectlon and frcqucncy: 

81 perccnt or more _______________________ .-+ 

t 25 to 40 percent ________ ~ ________________ ______ Average velocity: 

L-7: j . :. .... .::.rq .. j ndicatcs predominance of ncaufort 0-3 

fndicstca stmnger (0' '&.. .*o: knob), Jj::..::::!!:'..::::::::::' .,. .. . . , . . ... .... . .......I . . . . . . 

winds, Beaufort 4 (11 to 16 knota) and higher, dome 

Inant 60% or more of the tlme. 

CHART 3.-February. 

Figure 31.--Average surface wind drift direction, constancy, and force 

(from U.S. Weather Bureau 1943). 
90 

CflART C.-JUIV. 

Figure 31 (continued). 
91 

r;lI AHT B.-Octoher. 

CHART 7.-December. 
92 

5-28 - FEB 1971 

0 10 20 30 40 50 60 70 80 90 100 

FEB 1920-1970 

IO l020x)405060To8090Kx) 

8 42 

AUG (191 8-19 69)- SE P7 (1 8 8 5 - 19 69) 

It I,, 1, 8, 

0 IO 20 3040 5060 To 8090100 

14 AUG.-IS SEPT 1971 

LEGEND NUMBER OF -599 

OBSERVATIONS A KNOTS ROSE SCALE (PERCENI FREQUENCY) 

t 

Q 10 20 30 40 SO 

1 1 I I 

1 

I 

PERCENT FREOUENCY 4 WIND SPEED SUMMARY 

I (ALL DIRECTIONS) ' 

I 

34-47 

PERCENT 0-3 KNOTS '11-21 22-33. 

0 IO 20 3040 3060 To 809000 

PERCENT 

Figure 32.--Wind roses of historical data and 1971 data (from Huddell et al. 1974). 
93 
94 

R 4. 

Y, 

h 4 

-0 

4 

I 
95 
96 
97 
-v) 

I- .. - 

uC 

0' 

I 
99 
100 

NW N NE 

1% 

SE 

I 

Figure 40.--Direction of approach of tropical cyclones (34 kt) to Guam. Length 

of each line represents number of occasions on which cyklones approach from 

each octant of the compass, "The remainder of the storms (22%) displayed 

loops and stalls at their closest point of approach, or performed major deviations in track making it difficult to assume a uniform direction of 

motion." (from Ho'lliday 1975). 
101 

Figure 41.--Looping or stalling storms in the vicinity of Guam (from Holliday 

1975). 
102 

Figure 42.--Major changes in direction of storm movement (290c7) of Guam 

(from Holliday 1975). 
103 

Longitude t O E 1 

Figure 43.--Maximum sustained winds equal to or greater than 40 knots and in 

40-80, 81-120, and greater than 120 knot ranges versus longitude for 

typhoons occurring during the years 1953-68; the number of cases consists of 

all reconnaissance aircraft observations which were taken at least 6 hours 

apart; most reports are near the cyclone center (from Gray 1970). 

600 

100 

Q 

n 

0 

V 

200 

0 

z 

DEC 

JAN 

FEB 

MAR 

APR 

MAY 

JUN JUL AUG SEPT 

40-80 KtS. 

81-120KlS. 

OCT NOV 

Figure 44.--Maximum sustained winds equal to or greater than 40 knots and in 

40-80, 81-120, and greater than 120 knot ranges versus month for typhoons 

occurring during the years 1953-68; the number of cases consists of all reconnaissance aircraft observations which were taken at least 6 hours apart; 

most reports are near the cyclone center (from Gray 1970). 
1.06 

a 

6 

4 

2 

0 

0 TROPICAL STORM I63 kt 0 TYPHOON ? 64 kt 

Figure 45 .--Monthly occurrence (1948-75) of tropical storm/typhoon passage 

within 180 nautical miles of Guam by 10-day interval (31-day months have 

last 11 days included in last 10-day period) (from Holliday 1975). 

6- 

4- 

- 

2I -- YR 48 49 50 51 52 53 54 55 56 57 58 59 

8- 

6- 

4 

2 

- 

YR 62 63 64 65 66 67 68 

00 

69 70 71 72 73 

0 TROPICAL STORM C 63 kt TYPHOON E 64 kt 

0 

60 61 

U74 75 

Figure 46.--Yearly frequency (1948-75) of tropical storm/typhoon passage 

2180 nautical miles of Guam (from Holliday 1975). 
105 

* 
106 

Figure 48.--Annual mean salinities at the surface (from Robinson 1976). 
Figure 49.--Salinity (ppt) at 10 meters? first quarter (from Barkley 1968). 
108 

F~WE 50.--SalLmiLq '(ppt) at 10 meters, second quarter (from Barkley 1968). 
109 

Figure 51.--Salinity (ppt) at 10 meters, third quarter (from Barkely 1968). 
110 

Figure 52.-- Salinity (ppt) at 10 meters, fourth quarter (from Barkley 1968). 
I 

2 2. 

21. 

2 0. 

19. 

18. 

I7 

16. 

15. 

14. 

13. 

Figure 

111 

lo 142. 143' 144. 145. 146. 147. 148. 149' 150.E 

I I I I 1 I I I 

34.7 

'V 

e 

0 

34.6 

I I I I I I I I 

i3.--Surface salinity (21,April-2 May 1971) (from deWitt 1972). 
112 

2 4O 

23. 

22. 

2 I. 

20. 

IS. 

18" 

17. 

16. 

15. 

c;i" 

34.7. 

4.7 

I I I I I 1 I I 

Figure 54.--Surface salinity (2-12 November 1971) (from deWitt 1972). 
11.3 

4OC 

20c 

3 oc 

v) 

Qf 

kW 

LU 40( 

z 

z 5oc 

- 

I 

I- 2 60C 

a 

70C 

80C 

900 

IO00 

21"N 20" 19" 18O 17" 16O 15" 

I I ' 34.' 

34.8- ---e 

135Cl 

3 

f -- 

I I I I I I I 

Figure 55.--Salinity in per mil along 142OE, 21 April-2 May 1971 (dashed 

lines represent the depths of the 370 and 135 cl/t isopleths (from 

deWitt 1972). 
114 

IO( 

20( 

3 O( 

v) 

e 

w 

Lu 

t- 40( 

z 

z 5oc 

7- 

ta 

- 

0" 60( 

701 

80C 

900 

IO00 

13 C 

- \34.9 34.8 -- ---- 

'-- /-34.1 3 34 : 6 5 J - 34.4 

1 

134-3 

34'2 

Figure 56,--Salinity in per mil along 142'E, 2312 Novahex 1971 (dashed 

lines represent the depths of the 370 and 135 cl/t isopleths) (from 

deWitt 1972). 
115 

TEMPERATURE ('C) 

\ 

\ 

\ 

I \ SALINITY 

v \ 

I I '\ B 

\ 

I 

I 

I 

I 

I 

I 

3a.s - 35.0 . I 

SALINITY (%I 

I a . 1 r . L I 1.020 I 1.W5 1.030 

DENSITY (~/ernJ) 

Figure 57.--Mean temperature, salinity, and density profiles in the vici 

of Cabras Island, Luminao Reef, and Glass Breakwater (February 1978- 

February 1979) (from Lassuy 1979). 

.nity 
116 

Figure 58.--T-S diagram for the vicinity of the proposed OTEC site at Guam 

(based on mean temperacure and salinity data, February 1978-February 1979) 

(from Lassuy 1979). 
117 

Figure 59.--Meridional section of oxygen content against thermosteric 

anomaly in logarithmic scale in the equatorial current system at 137'E 

in January 1967 (from Masuzawa 1967). 
118 

c 

c 

3 

4 n 

0 

W 

E5 

s 

Y 

r 

t 2 6< 

7. 

6 

9 

lo* 

4 

\ 

\ 

1 

I 

\ 

\ 

\ 

\ 

\ 

\ 

ceo;\ 1 

\ 

\ 

\ 

\ 

\ 

\ 

I 

\ 

/ 

1 

V . 1 v . 1 I 

75 

TOTAL CO, (Ig/kg) 

Figure 60.--Mean dissolved oxygen and total carbon dioxide profiles in the 

vicinity of Cabras Island, Lumina0 Reef, and Glass Breakwater, Guam 

(February 1978-February 1979) (from Lassuy 1979). 
119 

c 

2 

3 

4 

0 

0 

P 

*5 E 

Y 

E 

86 

7 

8 

4 

10. , 

Pod- 

% . . . . . I 1 1 , . . . . , , . . P 

Figure 61.--Mean nitrate-nitrite and reactive phosphate profiles in the vicinity 

of Cabras Island, Lumina0 Reef, and Glass Breakwater (February 1978-February 

1979) (from Lassuy 1979). 
C 

1 

2 

3 

n4 

0 

0 

x 

.- 

Y E5 

X 

c 

n. 

W 

Q6 

7, 

8. 

9. 

10. 

l( 

120 

PH (pHunit3 

/ 

{-T.A. 

I 

1 

\ 

\ 

\ 

f 

b 

1 

\ 

\ 

\ 

1 

1 

/ 

/ 

/ 

I I w 

105 rio 115 120 

TOTAL ALKALINITY (mi/ I) 

Figure 62.--Mean pH and total alkalinity profiles in the vicinity of Cabras 

Island, Lumina0 Reef, and Glass Breakwater (February 1978-February 1979) 

(from Lassuy 1979). 
121 

3 

a 

(d 

c, 

al 

k 

1 

U 

al 

a 

U 

E 

8 
122 
321 
124 
125 
126 

-/ 
127 
128 
129 
130 

h 

aJ 2 

2 

rl 

(d 

U 

*rl 

bo 

C 

rl 

0 

k 

0 

Q) 

u 

I: 

(d 

a 

(d 

+I 

E 

k 

'u 

k 

aJ 

e 

0 

U 

U 

0 

aJ 

k 

3 

U 

(d 

k 

ar 

aJ 

U 

aJ 

U 

(d 

w 

k 

1 

v) 

aJ 

VI 

I 

W 

s" 

b 

! 

N 

h. 

n 

aJln 

kb 

1m 

boor( 

*ri 

Frr 
131 

I I 

I 

I 

I 

t-l 

(d 

U 

.d 

bo 

0 

l-4 

0 

k 

0 

a, 

Y 

2 

C 

(d 

a 

(d 

c, 

k 

a, 

e fi 

01 

z 

8 
132 

t? 

c 

a, 

M 

4 

r-l 

(d 

U 

.d 

M 

0 

.-I 

0 

t-i 

0 

0) 

U 

3 

c 

cd 

a 

(d 

6 

0 

t-i 

w 

t-i 

a, 

P 6 

a, 

U 

a, cl 

a, 

$4 

1 

U 

a 

$4 

a, 

a, 

U 

a, 

U 

(d 

+I 

t-i 

1 

v) 

I 

(d 

a, 

v) 

I 

v 

.I 

E? 

I. 

h. 

n 

am 

kh 

1m 

Mor( 

.d 

k4 
133 

REGION 2 

Figure 75.--Monthly variation of sea surface temperature in selected areas (dots 

represent the absolute extreme value reported; the inner (shaded) and outer 

(unshaded) envelopes represent 50 and 95 percent of the data observed (from 

LaViolette 1970). 
134 

22 

21 

20 

19 

18 

17' 

I6 

15' 

14' 

13' 

1 I I I 1 1 1 I 

0 

28.0 

c 

e e 

e Y 

a 

e 

e* 

e 

8.0 

e 

c? 

I I I I I I I I 

Figure 76.--Sea surface temperature north of Saipan (21 April-.:! May 1971) 

(from deWitt 1972). 
135 

I 

24 a 

2 3O 

22' 

210 

200 

19' 

I e@ 

17* 

16O 

IS' 

Io 142O 143. 144' 145O 146. 147O 148. 149' 150.E 

I 1 I i I I I I 

. 

L 

8 

e 

e 

r0 0 

0 

I I I I I I I t 

Figure 77.--Sea-surfaee temperature north of Saipan (2-12 November 1971) 

(from deWitt 1972). 
136 

Figure 78. --Plot of mean month!y sea-surface renperaturps for a 10-year period 

at- Tanguisson Polnt, Guam (from, Jones et ab. 1976) 
Figure 79.--Mean temperature profile in the vicinity of Cabras Island, 

Lumina0 Reef, and Glass Breakwater, Guam (February 1978-February 1979) 

(from Lassuy 1979). 
138 

2 

-\ 

0 

0 ln 

- ---- --. - --- 

0 

1 

t 

0 

0 

om 

0 

z 

A 

v) 

2 

W 

L3 

I 

0 

0 

0 

m 
139 

800 

900 

1000 

21"N 20° 19" 18. 17O 16. 15O 

- 

- \/-

- 

I 1 I 1 I 1 I 

100 

200 

300 

v) 

e E 400 

s 

500 

W 

- 

I 

e- & 600 

0. 

700 t 

Figure 81.--Temperature along 142'E (21 April-2 May 1971) (from deWitt 1972). 
140 

IOC 

200 

300 

v) 

ce 

kW 

400 

E 

z 500 

X 

I 

I600 

0 

700 

800 

900 

IO00 

23ON 22' 21" ZOO 19' 18" 17. 

I I I I 1 1 I' 

I I I I I I I 

Figure 82.--Temperature along 142'E (1-12 November 1971) (from deWitt 1972). 
14 1 

c 

A:Point of observation 

B 

k-- -. .~ 20- OWN 

\ . 6 Point of observation by ET 

C 

Figure 83.--Vertical distribution of water temperature: A--9-13 July 1974; B-- 

28 May-1 June 1975; C--31 May-2 June 1976 (from JAMARC 1975, 1976, 1977). 
142 

---- 400-Ff BOTTOM CONTOUR 

Figure 84.--Mean depth (in feet) to the top of the thermocline, January 

(from Robinson 1976). 
143 

Figure 85.--Mean depth (in feet) to the top of the thermocline, February 

(from Robinson 1976). 
144 

Figure 86.--Mean depth (in feet) to the top of the thermocline, March (from 

Robinson 1976). 
3 45 

Figure 87.--riean depth (in feet) to the top of the thermocline, April (from 

Robinson 1976). 
146 

Figure 88.--Mean depth (in feet) to the top of the thermocllne, May (from 

Robinson 1976) ~ 
14 7 

Figure 89.--Mean depth (in feet) to the top of the thermocline, June (from 

Robinson 1976). 
148 

Figure 90.--Mean depth (in feet) to the top of the thermocline, July (from 

Robinson 1976). 
14 9 

x 

Figure 91.-Mean temperature (in feet) to the top of the thermocline, August 

(from Robinson 1975) 
150 

Figure 92.--Mean temperature (in feet) to the top of the thermocline, September 

(from Robinson 1976). 
. 

Figure 93.--Mean temperature (in feet) to the top of the thermocline, October 

(from Robinson 1976). 
152 

Figure 94.--Mean temperature (in feet) to the top of the thermocline, November 

(from Robinson 1976). 
153 

Figure 95.--Mean temperature (in feet) to the top of the thermocline, December 

(from Robinson 1976). 
154 

h k 5----;_---7-- rl 0 

i zl 
155 

15 7 
158 
159 

-. 
160 

8 s 
161 
162 
163 
164 
165 

167 
168 

22 

21 

20 

19' 

18' 

17' 

16' 

15' 

14' 

I I 1 I I I 1 I 

b 

-2.20 

2.15 

a2.10 

e e 

2.10 

I1 i 1 I I I 

5 10 IS 20 15 30 35 crn/*oc 

tURRENT SPEED 

2.. .- - . 1 I I I I' I I 

Figure 110 .---1!ynqtmi c topography in dynamic meters of the sea surface relative 

to the 1000-db surface (21 April-2 May 1971) (from deWitt 1972). 
169 

I" 142" 143' 144' 145' 146" 147" 148" 149O I 

-1-n- 

- 

22' 

2 I' 

20' 

19' 

18' 

17' 

16' 

15' 

14' 

e 

9.10 J 

I I I I 1 I 

5 10 15 20 25 30 35 cmlsec 

CURRENT SPEED 

I I 1 I i 1 I I 

OoE 

Figure 111.--Dynamic topography in dynamic meters of the 200-db surface relative 

to the 1000-db surface (from deWitt 1972). 
170 

I 

2 2O 

21. 

2 oo 

19. 

18. 

17. 

I6O 

I5O 

14' 

130 

lo l42O 143O 144O 145O l46O 147O 148' 149O 150.E 

I 1 1 1. I I I J 

b 

e e 

G 

e 0 

4f 

II I 1 II I 

5 10 15 20 25 30 35 cmIrec 

CURRENT SPEED 

I I I I 1 I I I 

Figure 112.--Dynamic topography in dynamic meters of the 500-db surface relative 

to the 1000-db surface (from deWitt 1972). 
171 

*- 

I 

24" 

23O 

22. 

21. 

20° 

19O 

I8O 

I7O 

16. 

I50 

I4 O 

lo 142O 143O 144O 145O 146O 947O 148O 149O 150.E 

1 1 1 I I I I 

2.30 2.25 

b 4 

I I I 1 1 I 1 

5 10 15 20 25 30 35 cm/roc 

CURRENT SPEED 

I I I I I I I I 

Figure 113.--Dynamic topography in dynamic meters of the sea surface relative 

to the 1000-db surface (2-12 November 1971) (from deWitt 1972). 
172 

14 

23 

22' 

21' 

20' 

19' 

18' 

1 '7' 

I 64 

IS' 

14' 

m 

& 

z, 

0 

L 

c 

w 

m 

1.20 

c 

1.25 

en 1.20 

II 1 I I I I 

5 IO I5 20 25 30 35 cm/rec 

CURRENr SPEED 

I I I I I I P I 

Figure 114.--Dynamic tupography in dynamic meters of the 200-db surface relative 

to the 1000-db surface (from deWitt 1972). 
173 

2 3O 

2 20 

21° 

2 0. 

I so 

I8O 

17" 

I6O 

15. 

I4O 

I I I I I I I I 

. .65 

.625 

.60 

.575 

.55 

00 

1 I I L I I I 

5 1Q 15 20 25 30 35 m/oec 

CURRENT SPEED 

I I I I 1 I I I 

Figure 115.--Dynamic topography in dynamic meters of the 500-db surface relative 

to the 1000-db surface (from deWitt 1972). 
174 

Explanation of symbols in map: 

K 

OY 

ESC 

Ts 

EK 

NK 

Li 

Jc 

SO 

TG 

YE 

KCC 

STCC 

NEC 

ECC 

MC 

SEC 

NGC 

O'F 

OF 

KF 

STC 

IOM 

KP 

W 

C 

Kuroshio 

Oyashio 

East Saghalin Current 

Tsushima Current 

East Korean Current 

North Korean Current 

Liman Current 

Sea of Japan Central Cold Current 

Soya Warm Current 

Tsugaru Warm Current 

Yellow Sea Warm Current 

Kuroshio Countercurrent 

Subtropical Countercurrent 

North Equatorial Current 

Equatorial Countercurrent 

Mindanao Current 

South Equatorial Current 

New Guinea Current 

Kuril front 

Oyashio front 

Kuroshio front 

Subtropical Convergence 

Izu-Ogasawara-Mariana Ridge 

Kyushu-Palau Ridge 

Warm eddy 

Cold eddy 

Figure 116.--Compiled schematic map of the Kuroshio and neighboring currents, 

oceanic fronts, and eddies based on CSK data (summer 1965, winter 1966) 

with reference to the geosyncline ridges; STCC=Subtropical Countercurrent 

(fron Uda 1970). 
-+)---- A 

P&td trench detpr mM JSOO fathom 

BASIN 

Figure 117.--Regional relationships in the western North Pacific Ocean (from 

Cloud et al. 1956). 
Figure 118.--Bottom topography along Mariana Archipelago (from Chase et al. 1968). 

~~~ ~~ 
177 

N 

179 

16 

14 

12 

IO' I I 

144' 146' 142O 

Figure 121.--General bathymetric chart of ,irchipelago area; contour interval 

is 6000 feet (1000 fathoms) (from Emery 1962). 
3' 3w 

Figure 122.--Bathymetric chart of Guam and vicinity; contour interval is 

600 feet (100 fathoms) on both land and sea floor; reef areas ahown by 

solid black pattern (from Emery 1962). 
181 

Figure 123.--Distribution of deep-sea sediments near Guam (from Emery 1962). 
RECENT TECHNICAL MEMORANDUMS 

i 

Copies of this and other NOAA Technical Memorandums are available from the National 

Technical lnformation Service, 5285 Port Royal Road, Springfield, VA 22167. Paper copies vary in 

price. Microfishe copies cost $3.50. Recent issues of NOAA Technical memorandums from the 

NMFS Southwest Fisheries Center are listed below: 

NOAA TM-NMFS SWFC 30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

Estimating age of spotted and spinner dolphins (Stenella 

affenuafa and Stenella longirosfris) from teeth. 

A. C. MYRICK, JR., A. A. HOHN, P. A. SLOAN, M. KIMURA 

and D. D. STANLEY 

(April 1983) 

Re-estimation of three parameters associated with anchovy 

egg and larval abundance: Temperature dependent incubation 

time, yolk-sac growth rate and egg and larval retention in 

mesh nets. 

N. C. H. LO 

(May 1983) 

“NMFS guidelines on economic valuation of marine 

recreational fishing” 

D. D. HUPPERT 

(June 1983) 

“Summary of environmental and fishing information on Guam 

and the Northern Mariana Islands: A review of the plankton 

communities and fishery resources of Guam and the 

Commonwealth of the Northern Marim? Islands” 

R. N. UCHIDA 

(July 1983) 

“Some data on dolphin mortality in the eastern tropical 

Pacific tuna purse seine fishery prior to 1970.” 

T. D. SMITH and N. C. H. LO 

(July 1983) 

“Precision of age determination of northern offshore spotted 

dolphins.” 

S. B. REILLY, A. A. HOHN, and A. C. MYRICK, JR. 

(August 1983) 

“Recovery of adult green turtles observed or originally tagged 

at French Frigate Shoals, Northwestern Hawaiian Islands.” 

G. BALAZS 

(August 1983) 

“Report of the workshop on long-range planning for the 

North Pacific albacore fishery.” 

D. J. MAGKETT, Editor 

(November 1983) 

Distribution of four dolphins (Stenella spp. and Delphinus 

delphis) in the eastern tropical Pacific, with an annotated 

catalog of data sources. 

W. F. PERRIN, M. D. SCOTT, G. J. WALKER, F. M. RALSTON 

and D. W. K. AU 

(December 1983) 

Annotated references to techniques capable of assessing 

the roles of cephalopods in the eastern tropical Pacific 

Ocean, with emphasis on pelagic squids. 

J. B. HEDGEPETH 

(December 1983)