HOTSPOTS
DEFINITION - volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere.
- Hypothesis for hotspots: Hotspots are fed by narrow streams of hot mantle rising from the Earths core-mantle boundary in a structure called a MANTLE PLUME. However, this hypothesis is the subject of a major controversy in Earth science.
- Hawaii, Réunion, Yellowstone, Galápagos, and Iceland are some of the currently most active volcanic regions to which the hypothesis is applied.
- Most hotspot volcanoes are basaltic which makes them explosive than subduction zone volcanoes, in which water is trapped under the overriding plate.
- Where hotspots occur in continental regions, basaltic magma rises through the continental crust, which melts to form rhyolites. These rhyolites can form violent eruptions.
- For example, the Yellowstone Caldera was formed by some of the most powerful volcanic explosions in geologic history. However, when the rhyolite is completely erupted, it may be followed by eruptions of basaltic magma rising through the same lithospheric fissures (cracks in the lithosphere).
There are 40 to 50 hot spots around the world, including near the Galapagos Islands and Iceland. Hot spots can create entire chains of islands, like the U.S. state of Hawaii. Hawaii is on the Pacific plate, an enormous section of the Earth in the Pacific Ocean that is constantly moving, but very, very slowly. Although the plate is always moving, the hot spot underneath it stays still. The hot spot
spewed magma that eventually became a chain of islands that rose over the surface of the water. These islands were created one right after the other as the plate moved, almost like an island factory.
Hot spots don’t always create volcanoes that spew rivers of lava. Sometimes, the magma heats up groundwater under the Earths surface, which causes water and steam to erupt like a volcano. These eruptions are called geysers. A famous geyser is Old Faithful in Yellowstone National Park in the U.S. state of Wyoming. When it erupts, the water is 95.6 degrees Celsius (204 degrees Fahrenheit) and can reach more than 55 meters (180 feet) high.
(http://education.nationalgeographic.com/education/encyclopedia/hot-spot/?ar_a=1)
spewed magma that eventually became a chain of islands that rose over the surface of the water. These islands were created one right after the other as the plate moved, almost like an island factory.
Hot spots don’t always create volcanoes that spew rivers of lava. Sometimes, the magma heats up groundwater under the Earths surface, which causes water and steam to erupt like a volcano. These eruptions are called geysers. A famous geyser is Old Faithful in Yellowstone National Park in the U.S. state of Wyoming. When it erupts, the water is 95.6 degrees Celsius (204 degrees Fahrenheit) and can reach more than 55 meters (180 feet) high.
(http://education.nationalgeographic.com/education/encyclopedia/hot-spot/?ar_a=1)