Unformatted text preview: r related to high
viscosity felsic magma
Form by violent eruption or collapse
Enormous calderas 10s of km in diameter can
form over continental hotspots (“supervolcanoes”
such as Yellowstone)
such Photograph by M. Williams, National Park Service, 1977 Montgomery, 1987 Calderas
The Toba Caldera in Sumatra,
Indonesia formed from a massive
supervolcanic eruption estimated at
that occurred 69,000 to 77,000
Largest known explosive eruption
on Earth in the last 25 million
Caldera is 100 km long, 30 km
wide. Blocking of sunlight by ash is thought to have led to a volcanic
winter (temperature dropped avg. 3 to 5 oC globally, and as much
as 15 oC at higher latitudes).
Speculated to have nearly led to human extinction!
So what if Yellowstone caldera (~ 60 km dia.) blew it’s top again?
Note: 3 major eruptions associated with Yellowstone hotspot are known
to have occurred 2.1 million, 1.3 million, and 640,000 years ago.
of ashfall from
the last major
ago) End of Lecture
Make sure you have read Chapter 4 (Volcanoes and
In preparation for next lecture, read…
Chapter 5 (Weathering and Soil (excluding section on
Chapter 6 (Sedimentary Rocks)...
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- Fall '13
- Volcano, Mafic lava, Calderas, Volcanic Cones, fluid mafic lava