Science ? Involving volcanoes?

It is believed that hot spots in the earth's mantle produce some of the volcanic eruptions we can observe at the surface.  Perhaps the best example of hot spot volcanism is the Hawaiian island chain.  Young, active volcanoes exist at the southeastern end of the chain; older, inactive volcanoes exist at the northwestern end of the chain.  Since the Pacific Plate on which Hawaii sits is moving northwestward, it is believed that the plate has been moving OVER a mantle hot spot, while the hot spot remains relatively stationary.  The northwestward motion of the plate is evidenced by magnetic stripes on the seafloor, but the sequence of volcanoes in the Hawaiian chain supports that evidence.

Most volcanoes that are not above "hot spots" are associated with plate boundaries, especially with subduction zones.  Their source is probably shallower than that of the "hot spot" volcanoes.  The melt supplied to hot spot volcanoes is believed to originate in the neighborhood of 800 km depth, or possibly even deeper.  Volcanism due to subduction is believed to result from melting that occurs only 100 or a few hundred km below the earth's surface.

Volcanoes occurring above subduction zones do not exhibit the "sequence" characteristics that one sees in a chain of hot spot volcanoes.  Above the hotspot, only a few volcanoes are active at any one time, and if the plate is fast-moving, the volcanoes will be spread out in a line from oldest to youngest.  However, many features are ambiguous; for example, the "Caroline hotspot" in the western Pacific is so close to a subduction zone that there is ongoing controversy about the origin of the Caroline Islands.

Hot spot volcanoes e.g. Hawaii and the Aleutian Arc are formed when magma rises from deep within the earth. The volcanic rock forms volcanoes. As the tectonic plates moves over these hot spots volcanoes are created and die. Divergent boundaries occur when one plate subducts beneath another causing the lithosphere to melt. Pressure then causes these molten rock to rise forming volcanoes.

The Magma that forms Hotspots volcanoes comes from deep within the earth and does not contain a lot of water H2O. Other kinds of volcanoes have more water in their magma. When the water rises up, it expands very fast and this makes other kinds of volcanoes have much more explosive eruptions.

The hotspots volcanoes are also called shield volcanoes as they have not so steep slopes and look like a shield.

Hope that answered your question.