Plate Tectonics & volcanoes
revision for exam
How volcanoes form at constructive plate boundaries;
At constructive plate margins the plates are moving apart this type of movement mostly happens under the ocean. The gap left is filled by basaltic magma rising up from the mantle below to form volcanoes. Some of these volcanoes have grown high enough to form volcanic islands, such as Hawaii. As this is id Baslitic lava it creates Shield volcanoes .
features of a SUPER VOLCANO
- explosive eruptions
- eruption collum penetrates stratosphere and could get around the world in a few hours!
- locally devastating
- sv's are found in craters called calderas and are many 100's kilometers wide
Formation Of A Super Volcano
- These begin when large reservoirs of magma collect deep in the Earth's crust. Magma continues to collect as the reservoir grows to an enourmous size under extreme pressure.
- A super eruption occurs when the pressurized magma raises overlying crust enough to create vertical fractures that extend to the planet's surface.
- One by one, magma begins to surge vertically along these new cracks, which forms a ring of erupting vents.
- Eventually, as the vents merge with each other, the large cylinder of land within the ring has nothing to support it. The remaining earth above the chamber crashes down into the magma below. This collapsing crust forces additional lava and gasses out around the edges of the ring further increasing the violence of the eruption that is now hundreds of times larger than a regular eruption.
- When the eruption ends it will leave behind a caldera, or large crater, just like the one that forms Yosemite National Park
Worldwide effects of Supervolcano eruptions
CASE STUDY: Lukaggar (Iceland)
- tonnes of sulpher in the atmosphere - This resulted in ALOT of Acid rain. It can also block UV rays, therefore blocking the sun, resulting in global tempretures dropping, reducing global warming.
- extreme weather - failure to grow crops due to the 'june snow'
- 25% of population died.
- death rates went up by 10,000
- Ash cloud - today would stop all air travel, for several months
- 8months of lava flowing out with 10 months of moderate explosive events
Positives of living near volcanoes!
Ash mixes with soil, making it much more fertile for farmers, resulting in them not needing to use fertilizer for many years! It often attracts tourism after the eruption as people want to see the permrent damage done to the surroundings. Get to have the benefit of Geothermal energy, for hot water and electricity like what has been used in Iceland.