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In , Réunion , Yellowstone , Galápagos , and Iceland overlying the most currently active. Most hotspot volcanoes are Basaltic because they erupt through oceanic Lithosphere (e.g., Hawaii , Tahiti ). As a result, they are less explosive than subduction zone volcanoes, which have high water contents. Where hotspots occur under continental crust, Basalt ic Magma is trapped in the less dense continental crust, which is heated and melts to form Rhyolite s. These Rhyolite s can be quite hot and form violent eruptions, despite their low water content. For example, the Yellowstone Caldera was formed by some of the most powerful volcanic explosions in geologic history. FOLLOWING THE TRAIL OF A HOT SPOT As the continents and seafloor drift across the Mantle Plume , "hot spot" volcanos generally leave unmistakeable evidence of their passage through Seafloor or Continental Crust . In the case of the Hawaiian hot spot, the islands themselves are the remnant evidence of the movement of the seafloor over the hot spot in the Earth's mantle. The Yellowstone hot spot emerged in the Columbia Plateau of the US Pacific Northwest . The Deccan Traps of India are the result of the emergence of the hotspot currently under Réunion Island , off the coast of eastern Africa. Geologists use hot spots to help track the movement of the Earth's plates. Such hot spots are so active that they often record step-by-step changes in the direction of the Earth's Magnetic Poles . Thanks to lava flows due to a series of eruptions in the Columbia Plateau , scientists now know that the Reversal Of Magnetic Poles takes about 5000 years, fading until there is no detectable magnetism, then reforming in the near-opposite direction. HOT SPOTS VERSUS ISLAND ARCS Hot spot volcanoes should not be confused with Island Arc volcanoes. While each will appear as a string of volcanic islands. Island arcs are formed by Subducting , converging tectonic plates. When one oceanic plate meets another, the denser plate is forced downward into a deep ocean trench. This plate melts and becomes new molten material that fuels a chain of volcanoes, such as the Aleutian Islands near Alaska . LIST OF HOTSPOTS has moved over the Hawaii hotspot, creating A Trail Of Underwater Mountains that stretch across the Pacific]]
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