3 - Volcanism and climate change Flashcards
Give some background information about Mount Pinatubo.
Located on island of Luzon(<100km from Manila), not recognised as potentially active volcano prior to 1991 - not monitored, USGS volcanologists supported Philippine volcanologists due to nearby US naval/air base, rapid geological survey of past volcano deposits conducted
Describe the eruption of Mt Pinatubo on the 15th of June 1991.
Plinian eruption cloud soared into stratosphere & pyroclastic flows devastated flanks of mountain - these filled valleys with thick deposits of ash and pumice that were remobilised every rainy season for over a decade to form mudflows/lahars, 2 hrs into eruption - umbrella cloud formed by it reached diameter of 1000km, volcano summit collapsed leaving 2.5km wide caldera now filled by lake,
How was a large death toll prevented during the eruption?
Volcanologists had analysed the mountain, predicting the eruption and warning the military/civil proteciton authorities, saving thousands of lives, including communities of indigenous Aeta people that resided on the volcano itself
What were the climatic impacts of the eruption?
Sulphur dioxide emissions, eruption plume, global cooling
Describe the eruption plume caused by the eruption.
Cloud reached a height of 17km at time of eruption, top of cloud reached 3/4 times higher than cruising altitude of civil aviation, material was dispersed by fast winds as it was located in the stratosphere(drier than the troposphere)
What were the impacts of the SO2 emissions from the eruption?
20 million tonnes of SO2 released into the stratosphere - it wrapped around the globe along the equator at first before dispersing and mixing in the stratosphere → they formed sulphate aerosols that formed distinct bands of dust that are able to scatter visible light before building up to a peak a few months after eruption → eventually, it was washed out of the atmosphere once it reached the troposphere
What were the impacts of global cooling following the 1991 eruption?
The continental regions of the Northern Hemisphere were colder(0.6C - King et al., 1993) during the summer, resulting in lower agricultural productivity - particularly in Asia where rice production is heavily influenced by monsoonal rainfall
What does it take for an eruption to have an impact on global climate?
High sulfur yields, strongly explosive eruptions that generate a convective column to great heights, eruptions at tropical latitudes
What are the wider consequences of volcanic forcing?
Volcanic footprints in ice cores(sulphate aerosols are trapped in polar ice, sometimes with tephra), NH volcanic summer cooling → agriculture causing food shortages & famines → faime years linked to epidemic outbreaks → social unrest and political upheavals leading to major historical transofrmation
