Introduction
Plate tectonics is the main process that produces volcanoes, at subduction, convergent, and divergent zones. Yet, we see volcanic activity without the plate tectonics. “Hotspots” are found around the world. Many people who hear of the term hotspots, think of volcanoes and then the association of Hawaii, since it is a very common known hotspot. The Glossary of Geology (1987) defines “hotspots” as “a volcanic center, 100 to 200 km across and persistent for at least a few tens of millions of years, that is thought to be the surface expression of a persistent rising plume of hot mantle material. “Hotspots” are not linked with arcs, and may or may not be associated with oceanic ridges.” “hotspots” are formed in the ocean by producing …show more content…
Plumes: A Geological Controversy, Gillian R. Foulger explores the debate and evidence found by scientists surrounding “hotspots.” Scientists have found that many hotspot tracks originate from a large igneous province. Large igneous provinces (LIPs) are defined by the Encyclopedia of Geology as “massive crustal emplacements of predominantly iron- and magnesium-rich (mafic) rock that form by processes other than normal seafloor spreading; they are the dominant form of near-surface magmatism on the terrestrial planets and moons of our solar system” (p. 316). Hotspots that reach the earth’s surface may have three distinct origins as discussed by Courtillot et. al (2003). Between the boundary of the lower mantle and core is the deepest approximately 15-20% show features such as the presence of a linear chain of seamounts with an age progression, large igneous provinces (LIPs) at the origin of the hotspot track, the He3 to He4 ratio are consistent with deep origin. Pitcairn, Samoan and Tahitian hotspots all seem to occur at the top of large, transient, hot lava domes or superswells in the mantle. The rest seem to be of upper mantle origins and may be caused by breaking of plates when they …show more content…
Yet, “Hotspots”—regions with particularly high rates of volcanism—are not necessarily associated with plate boundaries. Hawaii, the premier example, is thousands of kilometers from the nearest plate boundary yet exudes lava at a higher rate per unit area than at any other place on Earth. G. Foulger and J. Natland 2003, discuss the evidence, or lack there of, of the deep plume model through seismic analysis, especially at Yellowstone. The fact that hotspots are not fixed, “Hawaii has not remained stationary; it changed direction radically at the time of the bend in the Hawaiian-Emperor chain ~50 million years ago, when the Pacific plate did not change direction” (p.921). And that analysis of the petrology does not indicate temperatures required from mantle from a deep plume. Richard Monastersky states, “For plate reconstructionists, hotspots seemed an ideal benchmark for tracing plate motion in the past; they literally left a trail on a plate as it passed overhead…However, new evidence suggests that these benchmarks may actually be drifting” (p.250). This adds to the uncertainty about the origins of