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Most volcanic eruptions occur near the boundaries of tectonic plates, but there are some exceptions. In the interior of some tectonic plates, magma has been erupting from a relatively fixed spot below the plate for millions of years. As the plate continuously moves across that spot, a trail of progressively older volcanic deposits is left at the surface. The Hawaiian Islands are a good example of this. The island of Hawai‘i currently sits above the active hotspot, while a chain of older (and no longer active) island volcanoes extend to the northwest, in the direction of plate movement. A few hotspots (like the one in Iceland) have also been found at diverging plate boundaries.
Scientists don’t fully understand how and why hotspots occur, and there is vigorous scientific debate about their origins. A frequently-used hypothesis suggests that hotspots form over exceptionally hot regions in the mantle, which is the hot, flowing layer of the Earth beneath the crust. Mantle rock in those extra-hot regions is more buoyant than the surrounding rocks, so it rises through the mantle and crust to erupt at the surface.
Hotspots and their trails on the earth’s surface do not develop suddenly (within the span of a human lifetime, for example). Scientists are only able to identify hotspots because of their relatively fixed locations beneath the tectonic plates, which produce tracks of surface volcanism spanning millions of years.
Actually, the source of the hotspot is more or less stationary at depth within the Earth, and the North America plate moves southwest across it. The average rate of movement of the plate in the Yellowstone area for the last 16.5 million years has been about 4.6 centimeters (1.8 inches) per year. However, if shorter time intervals are analyzed, the plate can be inferred to have moved about 6.1...
Scientists use the term magma for molten rock that is underground and lava for molten rock that breaks through the Earth's surface.
Most earthquakes and volcanic eruptions do not strike randomly but occur in specific areas, such as along plate boundaries. One such area is the circum-Pacific Ring of Fire, where the Pacific Plate meets many surrounding tectonic plates. The Ring of Fire is the most seismically and volcanically active zone in the world.Learn more: U.S. Volcanoes and Current Activity Alerts
Over geologic time, volcanic eruptions and related processes have directly and indirectly benefited mankind:Volcanic materials ultimately break down and weather to form some of the most fertile soils on Earth, cultivation of which has produced abundant food and fostered civilizations.The internal heat associated with young volcanic systems has been harnessed to produce geothermal energy.Most of...
Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma. Since it is lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually, some of the magma pushes through vents and fissures to the Earth's surface. Magma that has erupted is called lava.Some volcanic eruptions are explosive and others are not. The...
The Galapagos Islands are perhaps best known for their unique species of plants and animals and their role in influencing Charles Darwin and others in...
Many of the islands that dot the center of the Pacific Ocean are made up of active, dormant, or extinct volcanoes, whose geologic histories are...