Hotspots

Question 1

What is a mantle plume?

Answer 1

a long cloud of smoke or vapour resembling a feather as it spreads from its point of origin.

Question 2

What is a hotspot?

Answer 2

• intensive radioactivity in the Earth’s interior creates a huge collumn of upwelling lava, known as a “plume”
• the plume of plastic rock from the Asthenosphere pushes upwards; pressure drops and the plastic rocks become molten, melting and pushing through the crust above.
• this lies at a fixed position under a Tectonic plate.

Question 3

What is anonalous volcanism?

Answer 3

Volcanic activity which occurs not at a plate boundary

Question 4

What is theory 1 of hotsots?

Answer 4

• As the plate moves over this “hotspot”, the upwelling lava creates a steafy succession of new vopcanoes that migrste along with the plate (kinda like a conveyor belt).
• The plume eats into or melts the plate above, so that the thickness of the crust at this point is much smaller than average
• these domes or plumes can of plastic rock can be up to 1000km across.
• some are now starting to doubt this theory

Question 5

Theory 2 of hotspots - 2003 G . Foulger

Answer 5

• she proposed that current volcanic anomalies away from plate boundaries cam be explained by weaknesses in plates themselves
• with all the movement that plates have gine through they’ve been pulled, scarred and stretched from collisions or divergences e.g. pacific as their edges are pulled down into subduction zones
• ## when the vulnerable parts of the crust pass over slabs of previously subducted material that melt easily in the conditions of lowered pressure, this sets up a stage for volcanic activity on a scale and are now known as hotspots.

Question 6

What is a deccan trap?

Answer 6

• TheDeccan Trapswere formed when the Indian tectonic plate was above a hotspot volcanocalledthe Reunion hotspot.
• layered area of flood basalts - up to 2000km thick
• covering an area of 500,000km2
• dated 65 million years ago

Question 7

Iceland

Answer 7

• does not fit well with theory 1 + 2
• sits on a divergent plate boundary
• as well as sitting on a divergent plate boundary
• also sits on top an unusually active hot spot beneath the Mid-Atlantic Ridge