Mount Baker—Living with an Active Volcano

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet-059-00

May 2000

M

USGS

MOUNT BAKER

Explosive eruptions

blast fragments of 

rock high into the air. 

Large fragments

fall to the ground

close to the

volcano.

Small fragments 

(called ash)

from the largest

eruptions can

travel hundreds

of miles.

Lahars are fast-moving slurries of

rock, mud, and water that look and

behave like flowing wet concrete.

Landslides can

transform into lahars.

Pyroclastic flows can

generate lahars

by melting

snow and ice.

TEPHRA

PYROCLASTIC FLOWS

LAVA FLOWS

VOLCANO HAZARDS

LAHARS

Lava is molten rock (magma) that

pours or oozes onto the Earth's

surface. Numerous eruptions of

lava interbedded with rock rubble

constructed Mount Baker.

AT

Pyroclastic flows

are hot avalanches

of lava fragments

and volcanic gas

formed by the

collapse of

lava flows

or

eruption

clouds.

Mount Baker (10,781 feet) viewed from east side with steam plume rising from Sherman Crater (left side of

summit, inset shows crater interior). Scar of the 1891 flank collapse is visible in lower left of photo. Photos by

Kevin Scott and (inset) Robert Symonds, USGS.

What Are the Hazards?

The next eruption of Mount Baker may

produce lava flows, pyroclastic flows,

volcanic ash (tephra), and lahars. Lahars are

by far the greatest concern at Mount Baker

because of its history of frequent lahars, the

ability of lahars to flow for tens of miles, and

the potential for hazardous future impacts of

lahars on two reservoirs on the east side of the

volcano. Tephra hazards at Mount Baker are

less important than at neighboring Glacier Peak

volcano to the south.

Lahars can originate in two ways:

1) During eruptions, pyroclastic flows can

melt snow and ice to create torrents of ash,

rock, and water that move downvalley as sandy

(noncohesive) lahars.

2) Because the volcano is locally weakened

and altered to clay by percolating, acidic, hot

water and steam (like that venting from

Sherman Crater), future volcanic landslides

known as flank collapses can mobilize to form

muddy (cohesive) lahars.

Lahars of collapse origin occur during

eruptions. They also occur during non-eruptive

periods triggered by regional earthquakes,

gravity, or increases in hydrovolcanic activity

not associated with magma intrusion.

When ground water comes in contact with

either magma or hot rock, hydrovolcanic

Washington, and Vancouver, British

Columbia. On cold, clear winter

days, dramatic increases in the

steam plume rising continuously

from Sherman Crater can alarm

local residents. This apparent

increase in plume vigor occurs

because of condensation of steam

in cold, calm air. In 1975, however,

increased steaming and melting of

snow and ice around Sherman

Crater did signify a change in heat

output from the volcano's interior.

Although the increased heat flow

gradually subsided, it could have

signaled the start of eruptive

activity, and precautions were

wisely undertaken.

So that the public can be warned

of, and be prepared for, future

eruptions and other hazardous

events at Mount Baker, U.S. Geological Survey (USGS) scientists

are studying the volcano's past

behavior and monitoring its current

activity.

ount Baker dominates the

skyline from Bellingham,

U.S. GEOLOGICAL SURVEY—REDUCING THE RISK FROM VOLCANO HAZARDS
400,000 and 300,000 years ago and formerly

bigger than today's Mount Baker.

Although numerous in Oregon and southern

Washington, cinder cones formed of the rock

type called basalt are rare around Mount Baker.

A cinder cone that formed 9,800 years ago in

Schriebers Meadow produced a widespread

tephra layer, and lava flows that reached the

Baker River.

Today's Mount Baker

Modern Mount Baker formed during and

since the last ice age, which ended about

15,000 years ago. Lava flows from the summit

vent erupted between 30,000 and 10,000 years

ago and, during the final stages of edifice

construction, blocky pyroclastic flows poured

down most of the volcano's drainages. An

eruption 6,600 years ago produced a blanket of

ash that extended more than 20 miles to the

northeast. This eruption probably occurred

from the presently ice-filled summit crater.

Subsequently, sulfurous gases have found two

pathways to the surface—Dorr Fumaroles,

northeast of the summit, and Sherman Crater,

Deposit of the largest lahar from Mount

Baker, exposed near the confluence of the

Middle and North Forks of the Nooksack

River, about 20 miles from its source at the

Roman Wall. Note the protruding logs and

branches from living trees that were

knocked down and carried by the lahar. Ice

axe, 3 ft, shows scale. Lahars are the

greatest hazard at Mount Baker. Inset

shows the flow front of a slurry of rock and

water, typical of lahars. The flow is about 10

feet deep, moving right to left at 20 miles per

hour. Photos by Kevin Scott, USGS.

Volcanic ash (tephra) layers on Mount Baker's south

flank. Lower white band is from an eruption of Crater

Lake, Oregon (7,700 years ago); upper yellow band is

from a hydrovolcanic eruption of Mount Baker (6,600

years ago). Above the yellow band is a black ash from

a magmatic eruption of Mount Baker (also about

6,600 years ago). Tephra hazards at Mount Baker are

less significant than at neighboring Glacier Peak

volcano to the south. Photo by Kevin Scott, USGS.

explosions of steam and rock can occur. Such

events, in addition to possibly triggering

collapse, can themselves be hazardous.

Mount Baker— Early History

USGS research in the last decade shows

Mount Baker to be the youngest of several

volcanic centers in the area and one of the

youngest volcanoes in the Cascade Range. Volcanic activity in the Mount Baker area began

more than one million years ago, but many of

the earliest lava and tephra deposits have been

removed by glacial erosion. The pale-colored

rocks northeast of the modern volcano mark

the site of ancient Kulshan Caldera that

collapsed after an enormous ash eruption one

million years ago. Subsequently, eruptions in

the Mount Baker area have produced cones and

lava flows of andesite, the rock that makes up

much of other Cascade Range volcanoes like

Mounts Rainier, Adams, and Hood. From about

900,000 years ago to the present, numerous

andesitic volcanic centers in the area have

come and gone, eroded by glaciers. The largest

is the Black Buttes edifice, active between

south of the summit. Both these area are sites

of pervasive bedrock alteration, converting

lavas to weak, white-to-yellow material rich in

clays, silica, and sulfur-bearing minerals. At

Sherman Crater, collapses of this weakened

rock created lahars in 1843 and as recently as

the 1970's.

Past Events — Future Hazards

Like most volcanoes, Mount Baker's history

records great variations in behavior. Scientists

believe the following case histories are good

examples of the range in size and types of

hazardous activity that have occurred in the

THOUSANDS OF YEARS AGO

12 10 8 6 4 2 0

Cinder 

cone

Sequence of events about 6,600 years ago

1843 1891 1975

Hydrovolcanic

explosion,

collapse,

lahars

Large

collapse,

large

lahar

Hydrovolcanic

explosion,

collapse,

large lahar

Collapse,

lahar

Collapse,

lahar

Collapse,

lahar

Multiple lava flows,

pyroclastic flows,

ash eruptions,

noncohesive lahars

Ash

eruption

AD

Increased

steam and

heat

Eruptions and flank collapses at Mount Baker Historical events

during the past 12,000 years 
WHATCOM COUNTY

SKAGIT COUNTY

Bellingham

Bay

EXPLANATION

Proximal pyroclastic flowage hazard zone - Area that could be 

 affected by pyroclastic flows and lava flows.

Inundation Zone I- Pathways for eruption-related lahars due to large 

 flank collapses or pyroclastic flows, or floods in the Skagit River

 valley caused by displacement of water in reservoirs by lahars.

Inundation Zone II- Pathways of lahars resulting from more frequent, 

 small-to-moderate flank collapses from the area of Sherman Crater.

North Fork Nooksack River

Maple Falls

Glacier

Lynden

Deming

Concrete

Lake

Whatcom

Lake

Shannon

Baker

Lake

Skagit River

Middle F ork Nooksack R. Black Buttes

Schriebers Meadow

Cinder Cone

Dorr Fumaroles

Kulshan 

Caldera

Roman Wall

Sherman Crater

Bak e r Riv

er

Bellingham

Sumas

Everson

Mount 

Baker

542

9

20

5

0 5 10 Miles

Sedro Woolley

Burlington

Mount 

Vernon

Map showing hazard zones for lahars, pyroclastic flows and lava flows (for more detail see Plate 1 in US Geological Survey Open-File Report 95-498).

past and could occur again. Small events are

more common than large ones, and during a

future hazardous event only parts of the hazard

zones shown on the map may be affected.

Flank Collapses, Lahars, and Tephra

Eruptions, about 6,600 Years Ago

A series of discrete events culminated with

the largest tephra-producing eruption in postglacial time at Mount Baker. First, the largest

collapse in the history of the volcano occurred

from the Roman Wall (see map) and transformed into a lahar that was over 300 feet deep

in the upper reaches of the Middle Fork of the

Nooksack River. It was at least 25 feet deep 30

miles downstream from the volcano and

probably reached Bellingham Bay. Next, a

huge hydrovolcanic explosion occurred near

the site of present day Sherman Crater,

triggering a second collapse of the flank just

east of the Roman Wall. That collapse also

became a lahar that mainly followed the course

of the first one for at least 20 miles, but also

spilled into tributaries of the Baker River.

Finally, an eruption cloud deposited several

inches of ash as far as 20 miles downwind to

the northeast.

Sherman Crater Forms in 1843

The present shape of Sherman Crater

originated with a large hydrovolcanic explosion. In 1843, explorers reported a widespread

layer of newly fallen rock fragments "like a

snowfall" and the forest "on fire for miles

around." Rivers south of the volcano were

clogged with ash, and Native Americans

reported that many salmon were killed. A short

time later, two collapses of the east side of

Sherman Crater produced two lahars, the first

and larger of which flowed into the natural

Baker Lake, raising its level at least 10 feet.

The location of this 19th-century lake is now

covered by waters of the modern damimpounded Baker Lake. Similar but lower level

hydrovolcanic activity at Sherman Crater

continued intermittently for several decades

afterwards.

Flank Collapse and Lahar in 1891

In 1891, about 20 million cubic yards of

rock fell from the scar shown in the photo on

the front page, producing a lahar that traveled

more than 6 miles and covered 1 square mile.
REASONS FOR THE CLOSURE

Based on scientific information obtained from the 

U.S. Geological Survey and scientists studying steam 

activity on Mt. Baker, the Forest Service has closed 

the shoreline and all campgrounds at Baker Lake.

The closure is in the interest of public safety.

There is danger that the heavy steam acitivity will 

trigger a massive mudslide from the upper slopes

of Mt. Baker. Such a slide could enter the lake 

with great force, sending a wave of water along

the lakeshore and into the campground areas.

This closure includes Horseshoe Cove, Boulder

Creek, Maple Grove, Baker Lake, Park Creek and

Shannon Creek Campgrounds as well as.......

CLOSURE CLOSURE

View looking north at Mount Baker summit, Sherman

Crater, and the Roman Wall. Photo by Dave Tucker.

This notice was posted at campgrounds around Baker Lake by the US Forest Service in June 1975. Normally,

Baker Reservoir approaches capacity during mid-summer. At most other times, reservoir levels are low enough

to impound lahars the size of those that occurred in 1843.

Sherman Crater Heats Up in 1975,

Triggering Concern

Beginning in March 1975, the rate of gas

and steam emission from Sherman Crater

increased significantly. Heat flow increased

more than tenfold. The activity gradually

declined over the next 2 years but stabilized at

a higher level than before 1975. Several small

lahars formed from material ejected onto the

surrounding glaciers. Acidic water was

discharged into Baker Lake for many months.

Response to the 1975 Activity—

Strategies for the Future

In 1975, scientists believed that the dramatic

increase in the steam plume and heat output

from Sherman Crater could herald either a new

magmatic eruption or hydrovolcanic activity

like that of 1843. Either of these possibilities

would have increased the risk of collapse,

raising concerns that lahars could flow rapidly

into Baker Lake or Lake Shannon, displacing

water and creating a flood surge or even

causing dam failure. The volcano was

subjected to the most intensive monitoring ever

applied to a Cascade Range volcano up to that

time. As time passed, no signs of rising

magma— earthquakes, significant changes in

gas composition, or surface deformation—

appeared. The main risk, therefore, was of

flank collapses and lahars similar to those of

1843 (Map Inundation Zone II). Had magmatic

activity been confirmed, a much larger collapse

and flow would have been possible (Map

Inundation Zone I), and a magmatic eruption

could have ensued like those between 30,000

and 10,000 years ago or that of 6,600 years

ago.

When magmatic activity does recur, all the

drainages of Mount Baker will be at risk from

lahars, and upstream areas will be at risk from

pyroclastic flows and lava flows in the hazard

zone shown on the map. The Dorr Fumaroles

are also a potential site of hydrovolcanic

explosions. Steep headwalls on the north flank

are also at risk of flank collapse, but Sherman

Crater is the most likely area on Mount Baker

for renewed failure.

On the basis of conclusions by USGS

scientists in June 1975, an interagency task

force advised lowering the level of Baker Lake

so that it could accommodate lahar inflow

without displacing water from the reservoir that

could have flooded the downstream Skagit

River valley. Because a lahar could also trigger

waves that would inundate areas around the

lake, shoreline residences, campgrounds, and

businesses were evacuated. On the basis of

recent research, the west side of Sherman

Crater, site of a previous collapse, could also

be unstable. Today, if there were a similar

increase in activity at Sherman Crater, USGS

scientists might also recommend drawdown of

Lake Shannon, the smaller downstream

reservoir that is the catchment for drainages

from the west side of the crater.

Monitoring for the Future

The University of Washington Geophysics

Program, in cooperation with the USGS,

monitors seismic (earthquake) activity at

Mount Baker and other Cascade Range

volcanoes. Seismic activity is the most

common precursor of magma intrusion, which

potentially could lead to an eruption. The risk

and potential size of flank collapse and lahars

increase progressively as magma rises toward

and into a volcano's edifice.

The USGS monitors gas emissions from

Sherman Crater in order to detect changes in

the volcano's "plumbing system" that may be a

warning of impending magmatic activity or an

increase in hydrovolcanic activity, and thus an

increased chance of eruption or collapse.

Preparing for the Future

Scientists do not know when an eruption or

other hazardous event like a flank collapse will

occur at Mount Baker, but surely they will

occur again. As Mount St. Helens taught us, it

is best to be prepared. The USGS works with

Federal, State, Provincial, and local agencies to

prepare for disruption that might accompany

renewed activity. A coalition of these agencies,

known as the Mount Baker and Glacier Peak

Facilitating Committee, has drafted a plan

outlining how agencies will work together in

the event of unrest at either volcano.

What You Can Do

• Learn about the volcano hazards that could

 affect your community, and determine

 whether you live, work, play, or go to school

 in a volcano hazard zone.

• Plan what you and your family will do if a

 hazardous event occurs.

• Participate in helping your community be

 prepared.

A few moments spent in preparation now

could keep you, your family, and your

community safe when Mount Baker next

erupts.

Kevin M. Scott, Wes Hildreth, and

Cynthia A. Gardner

Graphics and design by

Lisa Faust, Bobbie Myers, and Christine Janda

COOPERATING ORGANIZATIONS

U.S. Department of Agriculture, Forest Service

University of Washington, Geophysics Program

For more information contact:

U.S. Geological Survey

Cascades Volcano Observatory

5400 MacArthur Blvd., Vancouver, WA 98661

Tel: (360) 993-8900, Fax: (360) 993-8980

http://vulcan.wr.usgs.gov/

or

USGS Volcano Hazards Program

http://volcanoes.usgs.gov/

or

your local emergency management agency:

Skagit County (360) 428-3250

Whatcom County (360) 676-6681

See also Potential Volcanic Hazards from Future

Activity of Mount Baker, Washington

(USGS Open-File Report 95-498), and

What are Volcano Hazards?

(USGS Fact Sheet 002-97)

Printed on recycled paper U.S. GOVERNMENT PRINTING OFFICE: 2000 — 573-504/57001 Region No. 8