Supervolcanoes and calderas !
The Volcanic Explosivity Index- how big is a supereruption ?
VEI- 5 Plinian, Mt St Helens
VEI 3VulcanianMontserrat
VEI 1 Hawaiian
VEI 6 Ultra-plinian Mt Pinnatubo
VEI 8 Imagine 100 Pinnatubos erupting at the same time
Supervolcanoes and calderas !
• Caldera - created from large, explosive eruptions of felsic pyroclastic material. The caldera is created when the roof of the magma chamber collapses.
• Can be 10’s km’s across
• Different from a crater
E.g., • Yellowstone, WY, 1 m.y.
Huge caldera, so big it could only be seen from space
http://youtube.com/watch?v=Abg5-gLdEb0
Supervolcano !
Why are supervolcano eruptions so big ?
• A) There is a higher % of gas in the magma• B) The collapsing magma chamber roof helps
the eruption• C) The magma is more viscous• D) A large volume of magma was ready to erupt• E) Eruptions occur simultaneously from a ring of
vents.
http://www.cotf.edu/ete/movies/caldera.mov
Which type of volcano would you rather live beside and why?
Cinder coneStratocolcano(composite)Sheild volcanoSupervolcano with caldera