Lava Flows

Damage limited to the vicinity in the immediate area of the volcano.

 

Commonly destroy property in Hawaii and Iceland.

Fatalities rare due to slow speed of advancing lava flow.

Lava Flows

Lava Flows

Lava Flows

Streams of molten rock

Usually slow speed

-Only a few mph

-Can reach up to 60 mph

Lava FlowsKupaianaha

Started eruptions in 1983, by 2002, 189 structures destroyed and 13 km of highway covered with up to 25m of lava.

Flow through 2002

Lava Flows

-Fire threat

-Destroys most structures

-Affects large areas of farmland

-May dam rivers & modify drainage

Etna 1983

Lava Flows

Heimaey 1973Etna 1991

Lava Flows

Fire fountaining at Pu’u O’o, Hawaii, which has been erupting since 1983

Summit caldera of Mauna Loa volcano, Hawaii:A basaltic shield volcano

Pahoehoe lava flows at Pu’u O’o, Hawaii.

A’a lava flows, Pu’u O’o, Hawaii.

Lava from Pu’u O’o, Hawaii, enters the ocean.

Pyroclastic Flows

View From Space - Klyuchevskaya, Russia

Pyroclastic Flows

Fluid avalanche of rock material, hot ash and gas

-Highly destructive

-Typically faster than 80km/hr and up to 700°C

•Can incinerate, burn, and asphyxiate

Pyroclastic Flows

Nuee Ardente

Pyroclastic Flows- Nuée ardente

-Destroy life and property in their paths.

60 people, thousands of animals and fish, and hundreds of acres of lumber were destroyed by ash flows from Mt. St. Helens.

A Nuée Ardent killed 20,000 people when Mt. Vesuvius exploded and shed a pyroclastic flow across the village of Pompeii in 79 AD.

Nuée ardentes are flows of fast-moving currents of hot gas and rock (collectively known as tephra), which travel away from the volcano at speeds generally greater than 80 km/h (50mph).

Pyroclastic FlowsThe nuée ardente that was generated when Mt. Pelée erupted swept 6 km downslope through the town of St. Vincent.

Pyroclastic FlowsMt. Pelee– 1902 Nuee ArdenteAlmost the entire population of 30,000 people were killed within minutes of inhaling the hot gases and ash.

Pyroclastic Flows

Montserrat 1996

Pyroclastic Flows

Montserrat Montserrat

Mt. Pinatubo, June 12th, 1991An explosive Island Arc volcano in the

Philippines

Pyroclastic FlowsVesuvius:People and animals died instantly from the rushing cloud of hot gas and ash.

Tambora (1815)

10,000 people were killed by bomb impacts, tephra falls and pyroclastic flows.

By far the largest impact was on the Earth’s atmosphere.

The eruption plume reached 44 km above the earth, loading the stratosphere with ashes and gases.

Tambora (1815)Greatest impacts from pyroclastic flows and ash and gas eruptions.

Dust that reaches the upper atmosphere (stratosphere) can remain suspended and may cause global cooling for months or years after the eruption.-This is why 1815 is known as “the year without a summer”

Approximately 150 km3 of ash was erupted with the explosions.

Tambora (1815)

Global Surface Temperature Reconstruction

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Year

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“The year without a summer”

Pyroclastic Flows

1883 Krakatau

Krakatoa (1883)

On the Island of Rakata, Krakatoa was one of 130 active volcanoes in Indonesia (the country with the most active volcanoes in the world).

The volcano had been inactive for almost 200 years prior to a series of small eruptions that began in 1883.

Krakatoa began its eruptive stage on May 20, 1883 immediately following a strong earthquake (no sensors were there to measure it).

The first explosions were heard 160 km away and sent steam and ash upwards to a height of 11 km.

By August 11 three vents were active on the volcano.

On August 26 several loud eruptions took place over the course of the day sending dust and ash to over 25 km elevation into the atmosphere.

Krakatoa (1883)

On August 27, four very large eruptions began at 5:30 am.

The last of the four was the largest and could be heard from Sri Lanka to Australia, up to 4,600 km from the volcano.

23 km2 area of the island was gone following the fourth eruption.

Krakatoa (1883)

The caldera collapsed with the explosion, from an original height of 450m above sea level to 250m below sea level.

The pyroclastic flow was experienced at sea as far as 80 km away.

Ships experienced hurricane force winds loaded with tephra and smelling strongly of Sulfur.

An estimated 4,500 people died from the direct effects of the blast.

The blast itself is thought to have ejected 20 km3 of tephra.

Burn-related fatalities were recorded up to 40 km away from the blast.

Krakatoa (1883)

The collapse of the caldera, combined with the explosion, generated a massive tsunami with a maximum height at landfall of 45 m.

Coral blocks up to 600 tons were washed ashore.

The impact was greatest on the nearby islands.

Krakatoa (1883)

Along low lying coasts of Java the waves washed 8 km onshore, dragging people along with them as they washed back to sea.

An estimated 36,417 people were killed by the tsunami alone.

The tsunami was recorded as a small rise in sea level as far away as the California coast (20 hours after the fourth blast).

Ash from the volcano fell to Earth as far away as 2,500 km downwind over the days following the eruption.

Ash and gases in the upper atmosphere led to a lowering of global temperature by several degrees.

Krakatoa (1883)

Tephra-Airborne volcanic rock

-Consists of wide range of rock types

-Larger rocks fall closer to volcano; ash can travel thousands of kilometers

Bombs (64mm+), lapilli (2-64mm) and ash (2mm-)

Reticulite

Tephra

Tephra hazard

Tephra Large bomb (Etna)

Ballistic damage potential: Etna & Montserrat

Ash fall

Extensive property damage and fatalities can result from heavy ash falls.

Significant ash in the upper atmosphere can circle the globe in a matter of weeks.

Mt. St. Helens’ ash cloud

More than 80 commercial jets have been damaged by flying through volcanic ash clouds.

Ash fall

An ashfall 10 million years ago killed these rhinos that are preserved at Ashfall Fossil Beds State Historic Park, Nebraska.

Death was not by burial but by lung failure due to inhaling the ash.

Pyroclastic Flows

Volcanic Ash

Ash fall Ash damage potential

• May collapse roofs• Fine ash causes

breathing problems• May damage car and truck

engines• May interfere with plant

photosynthesis

Rabaul

Pinatubo

Ash fall Ash damage potential

-Provide source for lahars

-Disrupts transportation communication, power distribution, and electronics

-Crop and fishery damage and water contamination

-Human and livestock health problems Heimaey 1973

Ash fall

Heimaey 1973

Ash cloud: El Chichon 1983

Yellowstone eruptions:

2.1 Ma

Compacted ash deposits 20 cm thick 1500 km from eruptions site

Ash fell in Los Angeles & El Paso

Metres thick ashy mud deposits in Caribbean cores attest to massive reworking of ash

Global climatic impact unknown but probably catastrophic

Depth of ash from a future Yellowstone super-eruption

10 cm

30 cm

100 cm

1 cm

Lahar

Heimaey 1973

Lahars are large debris flows that originate on volcano flanks.

Lahars can surge tens or even hundreds of kilometers downstream from a volcano

Lahars can also dam rivers and which can lead to extensive flooding.

Lahars are fast moving mudflows that can engulf urban areas that are nearby the eruption.

Lahar

Heimaey 1973

Ecuador 's Inter Andean Valley , home to some three million inhabitants, is subject to the lahar activity of many volcanoes that border the valley.

Lahar

Heimaey 1973

Lahars can be the most devastating outcome of many volcanoes.

Water and debris rushed down the slopes, picking up more debris along the way.

A relatively small eruption of Nevada del Ruiz, Columbia, in 1985, generated a lahar when the volcano melted a 2.5 km2 area of snow and ice.

Lahar

Heimaey 1973

Nevado del Ruiz – Columbia

Lahar

Heimaey 1973

Example of a Hazard Map showing lahars and degrees of risk

at Pinatubo(Feb. 2002)

Lahar

Form from:

1)Snow/ice water mixed with debris

2)Pyroclastic flows mixed with river water

3)Rainfall on loose material (ash)

4)breaching of a crater lake

Lahar

Ruapehu (NZ)Rabaul (PNG)

-May bury land and property

-Can contain house-size blocks

-Largely controlled by shape of the land

Lahar Damage Potential

-May clog rivers, overspill banks and block channels

-Can contaminate water supplies

-Hazard may continue for years

Ruiz (Colombia)Pinatubo

LaharMudflow hazard map: Mount Rainier