Download Supervolcanoes

Supervolcanoes
How do supervolcanoes form? Use this information to label your diagrams…
1. Supervolcanoes form at destructive plate margins or over parts of the mantle that are really hot. These are
called hot spots. At these points magma moves upwards in the Mantle, hits the base of the earth’s crust and
melts it creating a huge chamber of magma. The hot spot is static but the Earth’s crust moves over
it. Yellowstone National Park is on top of a hotspot.
2. As the magma rises up through cracks in the earth’s crust it gets stuck and pools, melting the rock around
for thousands of years. A magma chamber is formed below the surface and the pressure of the magma
causes a circular bulge on the surface.
3. Over thousands of years the pressure builds up and the bulge eventually cracks, creating vents for lava to
escape from. The lava erupts out of the vents causing earthquakes and sending up massive plumes of ash
and rock.
4. As the eruption continues it drains the magma chamber and the land above collapse down over, creating a
caldera. This is a big crater left as a result of the bulge collapsing. Sometimes these get filled with water to
form a big lake such as Lake Toba in Indonesia.
What are the characteristics of a supervolcano?
Supervolcanoes are large depressions,
called calderas that are marked by a rim of higher land around their edges. They are very hard to spot at ground level
due to their size. The caldera at Yellowstone National Park is close to 100km long, 40km wide and 8km deep. They
emit enormous quantities of ash. About 2.1 m years ago the Yellowstone supervolcano erupted 2,500 times more ash
than Mount St Helens did in 1980. Supervolcanoes are eruptions and explosions of catastrophic proportions, on the
Volcano Explosivity Index (VEI) supervolcanoes are an 8 on a scale that runs from 1 to 8. Each leap up the scale
represents an increase of explosive scale of 10 times the power. Mount St Helens was VEI 5! They also affect a much
wider area than a normal volcano. The ash would settle over hundreds of square kilometres compared to that from a
normal volcano which would cover only a few square kilometres. They also have global impacts.
CHARACTERISTICS
Normal Volcano
Shape
Cone-like mountain –especially if it is a
composite volcano.
Size
Etna is 3km high and 140km in its
circumference.
Scale of emissions
Ash can travel a long way, lava travels
shorter distances.
Impact
Over a few km2
Supervolcano