supervolcanoes are massive volcanoes
develop at destructive plate margins, or over hotspots eg Yellowstone National Park, USA.
Formation at hotspots:
- magma rises through cracks in crust to form magma basin below surface. presence of magma causes bulge on surface several km wide.
- bulge eventually cracks, creating vents for lava to escape through. lava erupts causing earthquakes, sending up gigantic plumes of ash & rock.
- as magma basin empties, bulge no longer supported. collapses and more lava spewed out.
- after eruption, crater (caldera) left behind where bulge erupted. sometimes filled with water to form lake…