Heartbeat of a Volcano

Transcript (Download)

Three days ago, these lava flows erupted in fiery fountains.

Materials thrown up from the earth's interior have transformed this land.

Now rising water vapor and hot gases are the only signs of activity at the volcano's vent.

While the lava is still hot beneath its crust, scientists arrive to investigate the effects of the eruption.

We will join them.

Portable seismometers and a recording seismograph are set up to monitor the volcano.

The seismograph shows that activity continues below the surface.

The National Bureau of Standards, WWDH, Maui, Hawaii.

Next tone begins at 21 hours 15 minutes.

Greenwich Mean Time.

Some equipment has been destroyed by the lava flow.

Long sections of cable must be replaced.

Cable is laid across the new lava, beyond which a seismometer is positioned.

By cable, signals from the seismometer are transmitted to the Hawaiian Volcano Observatory, staffed by scientists of the United States Geological Survey.

Here, movements of the active volcano are continuously recorded, a clue to the dynamic forces within the earth.

On the island of Hawaii are two of the world's largest volcanoes, Mauna Kea and Mauna Loa.

East of Mauna Loa is Kilauea, one of the earth's most studied active volcanoes.

The activity we are investigating is on the east rift zone of Kilauea.

Fifteen kilometers away is Kilauea's summit.

At the summit, overlooking the caldera, is the volcano observatory.

From the observatory, cables go out to seismometers strategically placed around the mountain.

Sensor signals are transmitted to the observatory, where a bank of seismographs continuously records them.

Here we see the tracing during a relatively quiet period.

The needle crosses a previously recorded earthquake.

Suddenly, a new earthquake occurs, indicating movement of the volcano.

Most of these earthquakes can only be detected by sensitive seismometers.

They cannot be felt by man.

Tracings for a 24 -hour period reveal frequent earthquakes, as many as 50 to 100 a day of differing magnitudes.

The shaking of an earthquake lasts only a short time, but harmonic tremor may go on for days.

Harmonic tremor is probably caused by the movement of magma within the volcano.

Movement of magma may also cause changes in the shape of the volcano.

Changes in the tilt of the mountain slopes are measured with a sensitive leveling instrument, set up at the center of a triangle.

The corners of the triangle are marked by calibrated rods.

A change in the tilt of the land will move the rods up or down in relation to one another.

These changes are detected by the leveling instrument.

A tent protects the instrument from the influences of direct sunlight and wind.

Tilt triangles are set up at many locations on the volcano.

In weather of all kinds, repeated measurements of the tilt are made at each triangle.

From these measurements, calculations are made to show changes in the volcano's shape.

The results plotted on a graph show that during the last eruption, the volcano deflated rapidly, but that since then it has started to inflate once more.

As the swelling continues, hot gases are observed at the vent.

This degassing provides a rare opportunity to gather samples of gases from within the volcano.

Gases pass through metal tubing into a collecting jar.

The vent is closely watched.

Degassing accompanied by lava spatter may suddenly increase.

As swelling continues, the summit caldera expands.

To measure the expansion, a geotometer is positioned over a permanent marker on one side of the caldera.

A beam of light is directed at a reflector on the opposite side of the caldera, five kilometers away.

By measuring the travel time of light, the geotometer detects changes in this distance as small as a few millimeters.

Calculations show that the geotometer stations on the summit have moved apart several centimeters since the last eruption.

Further evidence that the volcano is inflating.

A few days later, observers at the vent report lava is rising.

The mounting activity is immediately reported to the observatory by radio.

As pressure continues to build within the volcano, lava overflows the vent.

Fifteen minutes later, the lava flows back into the vent, ending a short eruptive cycle.

The volcano erupts.

Though small in scale, this activity provides many of the features of a major eruption and a hint of what is to come.

Later, the portable seismographs show increasing harmonic tremor.

At some locations, the needle swings wide.

At others, the tracing narrows.

Data from several stations are plotted on a map and compared.

The data show that the greatest activity is closest to station number one, near the vent.

Continuing measurements suggest that molten rock is moving.

Overnight, lava forms a spatter cone at the vent.

Observers keep a close watch on the activity.

Lava gushes from the vent, flows only a few meters, and pours back into the vent.

The observers are in constant radio contact with the observatory, where seismographs record a sharp increase in earthquake activity.

Tilt and geotometer measurements show the mountain is still swelling.

After five hours, Kilauea has been in violent eruption.

The height of the fountain is constantly measured.

It has reached heights of 200 to 300 meters and is still rising.

Smaller vents have opened.

Lava spreads for kilometers around the site.

Hawaiian lava is one of the hottest and most fluid in the world.

A mighty river of lava has formed.

The cascade, a curtain of fire, is twice as high as Niagara Falls.

The fountain soars to heights of 500 meters, taller than the Empire State Building.

After nine hours of activity, the fountain begins to subside.

Rivers of lava still feed the falls.

The main fountain dies.

Lava flows back into the vent.

One of the most spectacular eruptions in Hawaiian history has ended.

The next tone begins at 15 hours, 20 minutes.

Date Of Production

1970

Abstract

Part of the AGI-EBEC Earth Sciences Series, produced in cooperation with the American Geological Institute. Illustrates the measurement of volcano and earthquake activity and changes in the shape of volcanoes. Shows scientists at work, and the stages of volcanic activity leading to a major eruption. Provides detailed footage of a substantial eruption of Kīlauea in Hawaii.

Description

A seismograph is shown alongside the opening credits, transitioning to shots depicting the aftermath of the eruption of Kīlauea, a volcano in Hawaii. Scientists from the United States Geological Survey's volcano observatory are shown taking instruments to the site to measure the effects of the eruption. These include sensors and seismographs to measure tremors and earthquakes, leveling instruments and rulers for measuring changes to the tilt of the volcano's slopes, slide rules used for making calculations, instruments for collecting volcanic gases, and a geodimeter used to measure the expansion of the caldera. The narrator notes that "direct observations are as important as the data supplied by instruments," as dramatic footage is shown of scientists taking observations near the erupting volcano. The scientists discuss their work via hand radios as lava begins to rise. The film cuts to scientists discussing the seismograph "going wild" and footage of major volcanic eruptions. The credits roll as the seismograph continues to beep and measure the volcano activity.

Format

16mm

Extent

700 feet

Color

Color

Sound

Optical

Reel/Tape Number

1/1

Has Been Digitized?

Yes

Language Of Materials

English

Element

Print

Genre

Educational

Form

Short

Subject

Science
Nature
Volcanoes

Related Collections

Bert Van Bork Collection

Related Places

North America ➜ United States ➜ Hawaii

Distributor

Encyclopaedia Britannica

Main Credits

Van Bork, Bert (is producer)

Additional Credits

Encyclopaedia Britannica (is contributor)

Sam Allen (is writer)

Ulf Bäckström (is editor)

Van Bork, Bert (is cinematographer)

David Diederich (is contributor)

Participants And Performers

John S. Shelton (is participant)

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