Any Geologists out there? I need help with tectonic plate movement and volcanoes?

Question

Very briefly... If volcanoes form at the edge of plates, how did Hawaii form, being slap bang in the middle of the Pacific plate?

Answer 1

Volcanoes occur anywhere where something causes the underlying rocks of the mantle to partially melt producing magma. This happens in three main settings:
1) Where plates are moving apart (as in rift zones, and mid ocean ridges) which causes the hot mantle rocks to move towards the eart's surface causing decompression melting.
2) Above subduction zones (such as around the Pacific rim), where the subducting plate heats up releasing water (and CO2 etc), lowering the melting point of the overlying mantle wedge causing it to partly melt.
3) Within rising mantle plumes. Upwelling of the mantle wihin the plumes also leads to decompression melting ans magam generation.

The latter case is not always associated with a plate margin, as in Hawaii.

Answer 2

Whomever told you that volcanoes [only] form at the edge of plates misinformed you. If you go to the Great Rift Valley in east Africa you will find many volcanoes far from the edge of a boundary on the African Plate. There is also the matter of the Yellowstone Caldera Complex, once again, away from the edge of a boundary on the North American Plate. Think Hotspots. Some geologists don't believe they exist but Slab Pull is a weak theory compared to Plate Tectonics.

Answer 3

It's over a hot spot - as the plate moves over the hot spot, magma rises to develop an island. The plate moves on, but the hot spot stays in the same place, so a new island is made. If you look at the Hawaiian islands, they are in a bent line shape - the change in the direction of the plate movement has caused a change in the line of islands. If you're really smart, you can plot the speed and direction of plate movement from the relative positions of the islands.
A hot spot is where a mantle plume reaches the surface - ie where molten rock bubbles up to the surface.

Answer 4

Hawaii is formed on the top of a hot spot. A hot spot is generally formed when a column of magma called a magma plume rises from deep within the mantle and weakens the crust above it. Knowing that the crust moves due to plate movement and magma plumes are stationary, hot spots form volcanic chains or in the case of Hawaii, volcanic island chains.

Answer 5

its over an area where the oceanic crust is very thin, thus the magma from inside the earth gets through, it cools underwater, until there is so much magma released that it makes islands.

Answer 6

hard question. sorry, i have no idea about it.