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Clerical:
It's Volcano Video Week!
Homework #5 is posted. It will be completed in class today (10/2).
Before Thursday's class, take a virtual field trip
to Haimey. Then watch this 30 minute CBC video of the eruption.
Themes of the Day:
- Types of Volcanoes
- Felsic Magmas
- Stratovolcanoes
- Pyroclastic Eruptions
Types of Volcanoes
- volcanoes, lava flows
- Profile of a volcano, and types of eruption dictated by composition of the magma (lava) - Types of Igneous Rocks
- Main types of volcanoes and volcanic products:
- Shield Volcanoes - low viscosity basaltic magmas - lava lakes and flows common - not explosive - flood basalts and submarine pillow lavas are basaltic, too
- Cinder Cones - variable composition, often basaltic - usually a single batch of magma - steep cones formed by cinders piled around vent at angle of repose
- Composite Volcanoes (Stratovolcanoes) - interayered lava flows and pyroclastic deposits - ranges from intermediate to felsic in composition (andesite-dacite-rhyolite) - in volcanic arcs above subduction zones
- Dome Volcanoes - similar in composition and often genetically related to composite volcanoes - usually more viscous (more silicic) magma type (dacite/rhyolite) - pyroclastic flows abundant - explosive eruptions common
- Continantal Calderas - in continental regions the result of the largest types of volcanic eruptions - large, shallow, silicic magma chambers empty catastrophically with unparalleled violence; roof of magma chamber collapses into emptied portion of magma chamber
- Crater vs. Caldera - Aniakchak Volcano
- USGS Photo Glossary of Volcanic Terms - lots of good illustrations of volcanoes and volcanic features
Felsic Magmas
- formed by evolution of mafic magmas and melting of the crust
- Generally formed at subduction zones, by fractional crystallization and evolution of mafic magmas. Evolve
into intermediate to felsic composition magmas before crystallizing as diorite/andesite or granite/rhyolite.
- high viscosity - gas rich - explosive
Stratovolcanoes
Pyroclastic Eruptions
Mt. Pinatubo Overview
 The
goal of this exercise is to get you to think about the very real links between geology and society. Mount Pinatubo
in the Philippines erupted spectacularly in 1991 - it was the second largest eruption of the 20th century. The
video that we will watch on Monday details the monitoring and prediction efforts of
US Geological Survey (USGS) volcanologists and their colleagues at the
Philippine Institute for Volcanology and Seismology (PHIVOLCS).
Thousands of lives were saved because geologists were able to accurately predict the timing and magnitude of the
eruption - the Mt. Pinatubo eruption is considered one of the greatest success stories of modern volcanology. As
further evidence of its impact on our culture, consider that the movie
Dante's Peak draws much of its scientific inspiration from the story
portrayed in this video.
For further surfing...
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