Thursday, October 29, 2009

Volcanoes and Climate Change - John Seach

Large volcanic eruptions can cause global climate change and even be responsible for mass extinctions.

Major eruptions in Kamchatka Peninsula, Russia have a disproportional effect on global climate, due to the low troposphere elevation at these latitudes, and the ease of dispersal of ash, aerosol, and gas.

Most mass extinctions during the last 500 million years coincide with eruptions of large igneous provinces. The Cretaceous-Tertiary extinction was synchronous with the Deccan flood volcanism.

There is a positive feedback between glacial variability and atmospheric CO2 concentrations: deglaciation increases volcanic eruptions, raises atmospheric
CO2, and causes more deglaciation. Conversely, waning volcanic activity during an interglacial could lead to a reduction in CO2 and the onset of an ice age.

The eruption of Tambora volcano in Indonesia (1815) caused a change in global temperatures. Following the eruption parts of Europe and North America experienced a wet and cold summer season (year without a summer).

The Huaynaputina eruption in Peru, 1600 (VEI 6) coincided with low tropical temperatures, which were 0.44 deg C colder than in the year following Tambora eruption in Indonesia (1816).

Large explosive volcanic eruptions recorded in the historical volcano record
and in polar ice cores over the past 5000 years have produced mid-latitude warm-season cooling with potential effects across the northern hemisphere or globe.

Supercontinent breakup is caused by two events - mantle plumes and global warming. The breakup of Pangea, the last supercontinent, was accompanied
by eruption of the largest known continental flood basalt, the Central Atlantic Magmatic Province, which caused massive extinctions at the Triassic-Jurassic boundary.

The eruption of Krakatoa volcano in 1883 cooled the global climate and caused a drop in sea level. Even though the oceans were gradually warming because of changes in Earth's climate, sea level didn't return to its pre-Krakatoa height until about 1950.

Mud volcanoes are a source of methane (CH4) flux to the atmosphere and the ocean.

Large volcanic eruptions cause a depletion of atmospheric ozone. This happened after the eruption of Pinatubo volcano, Philippines, in 1991. Global ozone was reduced by 5% compared to the 1964-1980 average.