Gases that escape in the greatest abundance from volcanoes are:

-water vapor

-carbon dioxide

-hydrogen chloride

-nitrogen

-sulfur dioxide

Volcanic gases play an important role in the Earth System. Carbon dioxide, on the early earth, was emitted from volcanoes and converted to oxygen by photosynthetic algae.

Volcanoes & The Atmosphere

Volcanic activity gave the early Earth much of it’s atmosphere. (carbon dioxide and nitrogen).

Volcanoes & The Atmosphere

Water vapor is essential to the Earth system. Most of Earth’s surface water seems to have been released from the Earth’s interior by volcanoes.

Volcanoes & The Water Cycle

Volcanoes produced the atmosphere and the oceans

N2 CO2 H2O

Volcanic Emissions Flow Chart

N2 O2 oceans

99% of atmosphere

remains photosynthesis condensation

Volcanoes and the Earth System

Cosmos

High concentrations of carbon dioxide near a volcano are hazardous because they cause people and animals to suffocate.

Dangerous Gases

Lake Nyos - Cameroon

Lake Nyos - Cameroon

If the air that we breath has more than 10% CO2 it becomes deadly because it displaces the Oxygen that we need for respiration.

Lake Nyos, Cameroon, is a very deep lake within a volcanic crater.

The lake is so deep that hydrostatic pressure forces CO2 to remain at the lake bottom.

When the pressure of the CO2 exceeds a certain limit the gas rapidly bubbles up out of the lake and flows as an invisible gas cloud down the adjacent slopes.

On August 16, 1986 such a gas release flowed 19 km suffocating 1,700 people along its route.

Lake Nyos - Cameroon

Lake Nyos - Cameroon

Lake Nyos - Cameroon

The fountain lifts CO2 up to the surface so that it no longer accumulates.

Lake Nyos - Cameroon

Mammoth Mountain is a relatively young volcano that is emitting large volumes of CO2.

Gas concentrations in the soil in some areas near the mountain are high enough to kill trees and small animals.

Mammoth Mountain. California

Mammoth Mountain. California

Formation of acid rain (from sulfur dioxide SO2) can cause water contamination and plant damage Prevailing winds can blow gases thousands of kilometers away

Acid Rain

tropospheric aerosol cloud(lifetime 1 - 3 weeks)

large explosiveeruption(e.g. Tambora)

large effusiveeruption(e.g. Laki)

tropospheric cooling

stratospheric aerosol cloud(lifetime 1 to 3 years)

ashfall

stratospheric warming

reducedsolar flux

ballistics

SO2

SO2

H SO2 4

SO2

H SO2 4H S

2

incoming solar radiation

reflected andscatteredsolar flux

solar fluxabsorbed inthe infra-red

absorption ofupwardinfra-redflux

CO2

N2

H O2

Climatic Effects

Global Climate Change

SO2 (sulfur dioxide) in the upper atmosphere reduces incoming solar radiation.

SO2 from an eruption forms tiny droplets of sulfuric acid in the upper atmosphere.

The droplets significantly increase global albedo…..a negative radiative forcing that leads to cooling.

Mt. Pinatubo (1991) released 22 million metric tons of SO2 and reduced the Earth’s average temperature by 0.5 degrees Celsius in the year following the eruption.

•  Largest known historic eruption → 200 Mt sulphate aerosol in stratosphere

•  1816 one of coldest northern hemisphere summers of last 600y

•  Extreme weather –  June snow in eastern North Am. –  Summer killing frosts led to near total failure of crops in New England

–  Europe Summer T 3ºC cooler than 1951-70 average •  Cooling effect continued for 3 years •  1816-19 ‘last great subsistence crisis in western

world’ bread riots; famine; typhus & cholera

Tambora & ‘the year without a summer’

Tambora & ‘the year without a summer’

Global Surface Temperature Reconstruction

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Monitoring Volcanoes •  Seismicity •  Ground Movements

– Tiltmeter – GPS

•  Visual Observations: – Gas Geochemistry – Water Temperature