Hilo

Honolulu

P a c i f i c O c e a n

Lo‘ihi

Mauna Loa Kïlauea

Hualälai

Haleakalä

Hawai‘i

Maui

Moloka‘i

Kaho‘olawe

Lana‘i

O‘ahu

Kaua‘i

Ni‘ihau

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 074–97, version1.1

Revised June 2000

Living on Active Volcanoes—The Island of Hawai‘i

U.S. GEOLOGICAL SURVEY—REDUCING THE RISK FROM VOLCANO HAZARDS

People on the Island of Hawai‘iface many hazards that come

with living on or near active volcanoes. These include lava flows, explosive eruptions, volcanic smog,

damaging earthquakes, and tsunamis

(giant seawaves). As the population

of the island grows, the task of reducing the risk from volcano hazards becomes increasingly difficult. To help

protect lives and property, U.S. Geological Survey (USGS) scientists at

the Hawaiian Volcano Observatory

closely monitor and study Hawai‘i’s

volcanoes and issue timely warnings

of hazardous activity.

Late in the evening of June 1, 1950, after

many residents of Hoÿokena-mauka village

on the west coast of the Island of Hawaiÿi

had already gone to bed, Mauna Loa Volcano

suddenly began to erupt. Hot, glowing lava

poured from fissures and rushed down the

southwest flank of the volcano. In only 3

hours, the swiftly flowing lava traveled 14

miles and entered the village. The darkness

was lit by flames as the molten lava consumed several houses and the Post Office. By

daybreak, lava flows had crossed the area’s

only road in two places, cutting off all escape

routes. Fortunately, the residents of

Ho‘okena-mauka escaped unharmed, but for

some it was a close call.

The Island of Hawai‘i is composed of five

volcanoes, two of which—Mauna Loa and

Kïlauea—have erupted repeatedly in this

century. Another of these volcanoes,

Hualälai, last erupted in 1801 and has the potential to erupt again within our lifetime.

Most eruptions at Hawaiian volcanoes are

not explosive and are characterized by the

relatively quiet outflow of very fluid lava.

These eruptions can still be deadly, because

the lava may be erupted in huge volumes,

and on steeper slopes fluid lava can rapidly

travel many miles from its source.

Mauna Loa, the world’s largest active volcano, last erupted in 1984. During that 3-

week-long eruption, rivers of lava came

within 4 miles of the outskirts of the coastal

city of Hilo. Most of Mauna Loa’s eruptions

in the last 150 years began at eruption sites

(vents) near the volcano’s remote 13,677-

foot-high summit. About half of these summit eruptions quickly developed into eruptions on the flanks of the volcano. Mauna

Loa's flank eruptions usually occur along one

of two zones of weakness, called rift zones,

that extend partway down its northeast and

southwest slopes. A few eruptions also have

taken place from isolated vents on the

volcano’s northern slope.

Eruptions from Mauna Loa’s northeast rift

zone can send lava flows coursing toward

distant Hilo. However, those on the southwest

rift zone present the greater threat to life and

property, because residential areas developed

since the volcano’s 1950 eruption lie immediately downslope of potential vents.

Kïlauea Volcano, Mauna Loa’s younger

neighbor, tends to have long-lasting eruptions. Kïlauea’s ongoing eruption, which began in 1983, is already the volcano’s most destructive in this century. From 1983 to 1991,

lava flows repeatedly invaded communities

on Kïlauea’s coastal south flank, burying 8

miles of highway and destroying 181 houses

and a visitor center in Hawai‘i Volcanoes National Park. Most lava flows erupted since

1992 have remained within the National Park,

but Kïlauea’s geologic history indicates that

future activity will again threaten residential

areas on the volcano’s south flank.

Although Kïlauea’s eruptions tend to last

longer, Mauna Loa poses a greater hazard

because of the enormous volumes of lava it

In 1990, flows of lava from Kïlauea Volcano on the Island of Hawai‘i invaded Kalapana, a coastal community

treasured for its historic sites and black-sand beaches. Although the residents were able to evacuate safely,

their homes were incinerated, and by the end of that year all of Kalapana lay buried under 50 feet of lava. In

the past 1,100 years, more than 90% of Kïlauea ‘s surface has been covered by new lava flows. Ancient Hawaiian communities were able to easily relocate when threatened by lava flows, but modern communities,

with their greater dependence on permanent structures, highways, and utilities, are more vulnerable.

The Hawaiian Islands are at the southeast end

of a chain of volcanoes that began to form

more than 70 million years ago. Each island is

made of one or more volcanoes, which first

erupted on the sea floor and emerged above

the ocean’s surface only after countless eruptions. Most of the volcanoes active in the past

two centuries (red) are on the Island of Hawai‘i,

the youngest island in the chain. Haleakalä Volcano, on the Island of Maui, also erupts every

few centuries, most recently in 1790. Lo‘ihi, the

newest volcano, is still 3,000 feet beneath the

ocean’s surface.
magnitude

7.2

6 to 7

5 to 6

4 to 5

EARTHQUAKES

1929 to 1994

Kohala

Mauna Kea

Hualälai

Mauna Loa Kïlauea SW rift zone

NE rift zone

SW rift zone

E rift zone

Waimea

Hilo

Kailua

Kalapana

Lava flows erupted since 1800

Kïlauea lava flows erupted

 from 1983 to 1997

Volcano boundary

Increasing level of hazard

LAVA-FLOW 

HAZARD ZONES

Printed on recycled paper

produces and the greater steepness of its

slopes. Mauna Loa’s 1984 eruption paved 16

square miles of land with lava in just 3

weeks, whereas the ongoing eruption of

Kïlauea that began in 1983 took 3 years to

cover a comparable area.

Although explosive eruptions occur infrequently at Hawaiian volcanoes, they can be

devastating. In about 1790, Kïlauea exploded

in the deadliest eruption known to have occurred in what is now the United States. At

least 80 people were killed when a group of

Hawaiian warriors and their families was

overwhelmed by an extremely fast-moving

flow of hot gas and ash (pyroclastic surge)

near Kïlauea’s summit. Thick deposits of volcanic ash on the Island of Hawai‘i indicate

that much more powerful explosive eruptions

have occurred in prehistoric times.

Sulfur dioxide gas, continuously emitted

during Kïlauea’s current long-lived eruption,

has resulted in persistent volcanic smog

(“vog”) in downwind areas. Vog, as well as

acid rain, forms when sulfur dioxide gas reacts with atmospheric moisture. Vog aggravates respiratory problems, and acid rain

damages crops and corrodes metal. On the Island of Hawai‘i, the drinking water of many

homes with rainwater catchment systems has

been contaminated by lead leached by acid

rain from roofing and plumbing materials.

Earthquakes are another hazard associated

with active volcanoes, and the Island of

Hawai‘i experiences thousands each year. Most

of these are too small to feel, but about once a

decade a large quake shakes the entire island

and causes widespread damage. Before and

during an eruption, many small earthquakes occur as molten rock (magma) forces its way

through the upper parts of a volcano’s interior,

and such quakes often provide early warnings

of changes in eruptive activity. Deeper within a

volcano, stronger earthquakes can be triggered

by the stresses exerted by rising magma.

The most powerful earthquake to strike the

Island of Hawai‘i in the past century was the

Spectacular lava fountains are a common feature of

eruptions at Hawaiian volcanoes. This relatively small

lava fountain from Kïlauea Volcano was active in

1993. In the photo, a U.S. Geological Survey scientist

from the Hawaiian Volcano Observatory has just collected a sample of the newly erupted lava for analysis. The chemical composition and other characteristics of such samples can indicate impending changes

in a volcano’s eruptive activity.

The USGS Hawaiian Volcano Observatory (HVO) operates a network of seismometers to monitor the

thousands of earthquakes that the Island of Hawai‘i

experiences each year. Most of these are too small

to feel, but about once a decade a large quake

shakes the entire island and causes widespread

damage. To help protect people and property in the

large earthquakes that are certain to occur in the

future, HVO scientists are working with State and

local officials to ensure that building codes used on

Hawai‘i accurately reflect the seismic hazard.

Lava flows are the volcano hazard most likely

to seriously threaten people and property on

the Island of Hawai‘i. The U.S. Geological Survey (USGS) prepares and periodically revises

maps of lava-flow hazard zones for the island.

These zones are based on the locations of

probable eruption sites, likely paths of lava

flows, and how frequently lava has covered

an area in the geologic past.

MAPS OF VOLCANO HAZARDS ON HAWAI‘I

For more information contact:

U.S. Geological Survey

Hawaiian Volcano Observatory

P.O. Box 51, Hawai‘i National Park, HI 96718

 Tel: (808) 967-7328, Fax: (808) 967-8890

http://hvo.wr.usgs.gov/

or

U.S. Geological Survey Volcano Hazards Program

http://volcanoes.usgs.gov/

See also What are Volcano Hazards? (USGS Fact Sheet 002-97),

Volcanic Air Pollution—A Hazard in Hawai‘i (USGS Fact Sheet

169-97), and Explosive Eruptions at Kïlauea Volcano, Hawai‘i?

(USGS Fact Sheet 132-98)

Christina Heliker, Peter H. Stauffer, and James W. Hendley II

Graphic Design by

Sara Boore and Susan Mayfield

Banner design by Bobbie Myers

COOPERATING ORGANIZATIONS

Center for the Study of Active Volcanoes,

University of Hawai‘i at Hilo

Dept. of Defense Pacific Disaster Center

Hawai‘i County Civil Defense

Hawai‘i Office of State Planning

Hawai‘i State Civil Defense

National Park Service

National Oceanic and Atmospheric Administration,

Pacific Tsunami Warning Center

magnitude 7.2 shock of November 1975. This

quake occurred beneath Kïlauea’s south flank

and generated huge ocean waves (tsunamis)

that caused two deaths and substantial damage

along the nearby coast. Such locally generated

tsunamis are extremely dangerous, because

there is no time to warn the public before the

waves strike. A strong earthquake should therefore be regarded by people near the coast as a

signal to leave immediately for higher ground!

(See Surviving a Tsunami—Lessons from Chile,

Hawaii, and Japan, USGS Circular 1187.)

To better understand Hawaiian volcanoes

and the hazards they pose, the Hawaiian Volcano Observatory (HVO) was established in

1912 at the summit of Kïlauea. The observatory, operated continuously by the U.S. Geological Survey (USGS) since 1947, studies current geologic activity at Hawai‘i’s volcanoes, as

well as evidence of past eruptions, earthquakes,

and other volcano hazards. HVO scientists use

this information to provide timely warnings to

local officials and the public, to assess longterm volcano hazards, and to make hazard-zone

maps that help guide land-use-planning decisions.

The progress of Kïlauea’s current eruption is

being closely tracked by HVO scientists. The information they provide on projected lava-flow

movements helps public safety officials determine

when it is necessary to evacuate residents or close

roads. On Mauna Loa, HVO instruments have detected swelling indicating that the volcano’s

magma reservoir has been refilling since its 1984

eruption. HVO scientists continue to monitor this

swelling and are watching for signs of increased

earthquake activity, such as that which preceded

the volcano’s last two eruptions.

By helping to educate residents, public officials,

and visitors about volcano hazards on the Hawaiian Islands, USGS scientists at HVO are enabling

people to lead safer lives in a setting where spectacular volcanic eruptions and damaging earthquakes occur. The work of HVO is part of the

USGS Volcano Hazards Program’s ongoing efforts to help protect people’s lives and property in

all of the volcanic regions of the United States, including Hawai‘i, California, the Pacific Northwest, Wyoming, and Alaska.