Hilo

HonoluluP a c i f i c

Oc e a

n

Lo‘ihi

KïlaueaMauna Loa

Hualälai

Haleakalä�

Hawai‘i

MauiMoloka‘i

Kaho‘olaweLana‘i

O‘ahu

Kaua‘i

Ni‘ihau

U.S. Department of the InteriorU.S. Geological Survey

USGS Fact Sheet 074–97, version1.1Revised June 2000

Living on Active Volcanoes—The Island of Hawai‘iU.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 volca-noes. These include lava flows, ex-plosive eruptions, volcanic smog,damaging earthquakes, and tsunamis(giant seawaves). As the populationof the island grows, the task of reduc-ing the risk from volcano hazards be-comes increasingly difficult. To helpprotect lives and property, U.S. Geo-logical Survey (USGS) scientists atthe Hawaiian Volcano Observatoryclosely monitor and study Hawai‘i’svolcanoes and issue timely warningsof hazardous activity.

Late in the evening of June 1, 1950, aftermany residents of Hoÿokena-mauka villageon the west coast of the Island of Hawaiÿihad already gone to bed, Mauna Loa Volcanosuddenly began to erupt. Hot, glowing lavapoured from fissures and rushed down thesouthwest flank of the volcano. In only 3hours, the swiftly flowing lava traveled 14miles and entered the village. The darknesswas lit by flames as the molten lava con-sumed several houses and the Post Office. Bydaybreak, lava flows had crossed the area’sonly road in two places, cutting off all escaperoutes. Fortunately, the residents ofHo‘okena-mauka escaped unharmed, but forsome it was a close call.

The Island of Hawai‘i is composed of fivevolcanoes, two of which—Mauna Loa andKïlauea—have erupted repeatedly in thiscentury. Another of these volcanoes,Hualälai, last erupted in 1801 and has the po-tential to erupt again within our lifetime.

Most eruptions at Hawaiian volcanoes arenot explosive and are characterized by therelatively quiet outflow of very fluid lava.These eruptions can still be deadly, becausethe lava may be erupted in huge volumes,and on steeper slopes fluid lava can rapidlytravel many miles from its source.

Mauna Loa, the world’s largest active vol-cano, last erupted in 1984. During that 3-week-long eruption, rivers of lava camewithin 4 miles of the outskirts of the coastalcity of Hilo. Most of Mauna Loa’s eruptionsin the last 150 years began at eruption sites(vents) near the volcano’s remote 13,677-foot-high summit. About half of these sum-mit eruptions quickly developed into erup-tions on the flanks of the volcano. Mauna

Loa's flank eruptions usually occur along oneof two zones of weakness, called rift zones,that extend partway down its northeast andsouthwest slopes. A few eruptions also havetaken place from isolated vents on thevolcano’s northern slope.

Eruptions from Mauna Loa’s northeast riftzone can send lava flows coursing towarddistant Hilo. However, those on the southwestrift zone present the greater threat to life andproperty, because residential areas developedsince the volcano’s 1950 eruption lie immedi-ately downslope of potential vents.

Kïlauea Volcano, Mauna Loa’s youngerneighbor, tends to have long-lasting erup-tions. Kïlauea’s ongoing eruption, which be-gan in 1983, is already the volcano’s most de-structive in this century. From 1983 to 1991,lava flows repeatedly invaded communitieson Kïlauea’s coastal south flank, burying 8miles of highway and destroying 181 housesand a visitor center in Hawai‘i Volcanoes Na-tional Park. Most lava flows erupted since1992 have remained within the National Park,but Kïlauea’s geologic history indicates thatfuture activity will again threaten residentialareas on the volcano’s south flank.

Although Kïlauea’s eruptions tend to lastlonger, Mauna Loa poses a greater hazardbecause 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 communitytreasured 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. Inthe past 1,100 years, more than 90% of Kïlauea ‘s surface has been covered by new lava flows. Ancient Ha-waiian 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 endof a chain of volcanoes that began to formmore than 70 million years ago. Each island ismade of one or more volcanoes, which firsterupted on the sea floor and emerged abovethe ocean’s surface only after countless erup-tions. Most of the volcanoes active in the pasttwo centuries (red) are on the Island of Hawai‘i,the youngest island in the chain. Haleakalä Vol-cano, on the Island of Maui, also erupts everyfew centuries, most recently in 1790. Lo‘ihi, thenewest volcano, is still 3,000 feet beneath theocean’s surface.

magnitude

7.2

6 to 7

5 to 6

4 to 5

EARTHQUAKES1929 to 1994

Kohala

Mauna Kea

Hualälai

Mauna Loa Kïlauea

SW ri

ft zo

ne

NE rift zone

SW ri

ft zo

ne E rift zone

Waimea

HiloKailua

Kalapana

Lava flows erupted since 1800

Kïlauea lava flows erupted from 1983 to 1997

Volcano boundary

Incr

easi

ng le

vel o

fha

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LAVA-FLOW HAZARD ZONES

Printed on recycled paper

produces and the greater steepness of itsslopes. Mauna Loa’s 1984 eruption paved 16square miles of land with lava in just 3weeks, whereas the ongoing eruption ofKïlauea that began in 1983 took 3 years tocover a comparable area.

Although explosive eruptions occur infre-quently at Hawaiian volcanoes, they can bedevastating. In about 1790, Kïlauea explodedin the deadliest eruption known to have oc-curred in what is now the United States. Atleast 80 people were killed when a group ofHawaiian warriors and their families wasoverwhelmed by an extremely fast-movingflow of hot gas and ash (pyroclastic surge)near Kïlauea’s summit. Thick deposits of vol-canic ash on the Island of Hawai‘i indicatethat much more powerful explosive eruptionshave occurred in prehistoric times.

Sulfur dioxide gas, continuously emittedduring Kïlauea’s current long-lived eruption,has resulted in persistent volcanic smog(“vog”) in downwind areas. Vog, as well asacid rain, forms when sulfur dioxide gas re-acts with atmospheric moisture. Vog aggra-vates respiratory problems, and acid raindamages crops and corrodes metal. On the Is-land of Hawai‘i, the drinking water of manyhomes with rainwater catchment systems hasbeen contaminated by lead leached by acidrain from roofing and plumbing materials.

Earthquakes are another hazard associatedwith active volcanoes, and the Island ofHawai‘i experiences thousands each year. Mostof these are too small to feel, but about once adecade a large quake shakes the entire islandand causes widespread damage. Before andduring an eruption, many small earthquakes oc-cur as molten rock (magma) forces its waythrough the upper parts of a volcano’s interior,and such quakes often provide early warningsof changes in eruptive activity. Deeper within avolcano, stronger earthquakes can be triggeredby the stresses exerted by rising magma.

The most powerful earthquake to strike theIsland of Hawai‘i in the past century was the

Spectacular lava fountains are a common feature oferuptions at Hawaiian volcanoes. This relatively smalllava fountain from Kïlauea Volcano was active in1993. In the photo, a U.S. Geological Survey scientistfrom the Hawaiian Volcano Observatory has just col-lected a sample of the newly erupted lava for analy-sis. The chemical composition and other characteris-tics of such samples can indicate impending changesin a volcano’s eruptive activity.

The USGS Hawaiian Volcano Observatory (HVO) op-erates a network of seismometers to monitor thethousands of earthquakes that the Island of Hawai‘iexperiences each year. Most of these are too smallto feel, but about once a decade a large quakeshakes the entire island and causes widespreaddamage. To help protect people and property in thelarge earthquakes that are certain to occur in thefuture, HVO scientists are working with State andlocal officials to ensure that building codes used onHawai‘i accurately reflect the seismic hazard.

Lava flows are the volcano hazard most likelyto seriously threaten people and property onthe Island of Hawai‘i. The U.S. Geological Sur-vey (USGS) prepares and periodically revisesmaps of lava-flow hazard zones for the island.These zones are based on the locations ofprobable eruption sites, likely paths of lavaflows, and how frequently lava has coveredan area in the geologic past.

MAPS OF VOLCANO HAZARDS ON HAWAI‘I

For more information contact:U.S. Geological Survey

Hawaiian Volcano ObservatoryP.O. Box 51, Hawai‘i National Park, HI 96718

Tel: (808) 967-7328, Fax: (808) 967-8890http://hvo.wr.usgs.gov/

orU.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 Sheet169-97), 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 bySara Boore and Susan Mayfield

Banner design by Bobbie Myers

COOPERATING ORGANIZATIONSCenter for the Study of Active Volcanoes,

University of Hawai‘i at HiloDept. of Defense Pacific Disaster Center

Hawai‘i County Civil DefenseHawai‘i Office of State Planning

Hawai‘i State Civil DefenseNational Park Service

National Oceanic and Atmospheric Administration,Pacific Tsunami Warning Center

magnitude 7.2 shock of November 1975. Thisquake occurred beneath Kïlauea’s south flankand generated huge ocean waves (tsunamis)that caused two deaths and substantial damagealong the nearby coast. Such locally generatedtsunamis are extremely dangerous, becausethere is no time to warn the public before thewaves strike. A strong earthquake should there-fore be regarded by people near the coast as asignal to leave immediately for higher ground!(See Surviving a Tsunami—Lessons from Chile,Hawaii, and Japan, USGS Circular 1187.)

To better understand Hawaiian volcanoesand the hazards they pose, the Hawaiian Vol-cano Observatory (HVO) was established in1912 at the summit of Kïlauea. The observa-tory, operated continuously by the U.S. Geo-logical Survey (USGS) since 1947, studies cur-rent geologic activity at Hawai‘i’s volcanoes, aswell as evidence of past eruptions, earthquakes,and other volcano hazards. HVO scientists usethis information to provide timely warnings tolocal officials and the public, to assess long-term volcano hazards, and to make hazard-zonemaps that help guide land-use-planning decisions.

The progress of Kïlauea’s current eruption isbeing closely tracked by HVO scientists. The in-formation they provide on projected lava-flowmovements helps public safety officials determinewhen it is necessary to evacuate residents or closeroads. On Mauna Loa, HVO instruments have de-tected swelling indicating that the volcano’s

magma reservoir has been refilling since its 1984eruption. HVO scientists continue to monitor thisswelling and are watching for signs of increasedearthquake activity, such as that which precededthe volcano’s last two eruptions.

By helping to educate residents, public officials,and visitors about volcano hazards on the Hawai-ian Islands, USGS scientists at HVO are enablingpeople to lead safer lives in a setting where spec-tacular volcanic eruptions and damaging earth-quakes occur. The work of HVO is part of theUSGS Volcano Hazards Program’s ongoing ef-forts to help protect people’s lives and property inall of the volcanic regions of the United States, in-cluding Hawai‘i, California, the Pacific North-west, Wyoming, and Alaska.