Intraplate Volcanoes- Although most volcanic rocks are generated at plate boundaries, there are a few exceptionally active sites of volcanism within the plate interiors. These intraplate regions of voluminous volcanism are called hotspots. Twenty-four selected hotspots are shown on the adjacent map. Most hotspots are thought to be underlain by a large plume of anomalously hot mantle. These mantle plumes appear to be generated in the lower mantle and rise slowly through the mantle by convection. Experimental data suggests that they rise as a plastically deforming mass that has a bulbous plume head fed by a long, narrow plume tail. As the head impinges on the base of the lithosphere, it spreads outward into a mushroom shape. Such plume heads are thought to have diameters between ~500 to ~1000 km.
Ring of Fire- The Ring of Fire is an area where a large number of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean.
Lava- hot molten or semifluid rock erupted from a volcano or fissure, or solid rock resulting from cooling of this.
Magma- hot fluid or semifluid material below or within the earth's crust from which lava and other igneous rock is formed by cooling.
Viscosity- the state of being thick, sticky, and semifluid in consistency, due to internal friction.
Silica Content- the dioxide form of silicon, SiO 2 , occurring especially as quartz sand, flint, and agate: used usually in the form of its prepared white powder chiefly in the manufacture of glass, water glass, ceramics, and abrasives.