Hotspot volcanoes

SUNDAY SPACE: Solar System volcanoes come in many varieties, shapes and sizes | Examiner

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There are different types of volcanoes on Earth. From the wide and short shield volcanoes of Hawaii to the craggy, tall, and explosive stratovolcanoes found at the edges of tectonic plates (think of the kind of volcano that destroyed Pompeii). But have you ever considered the types of volcanoes that might exist on planets other than Earth? On Earth, most of our volcanoes are driven by plate tectonics – the movement of large plates in the earth’s crust – where they collide or separate, causing magma to be released below the surface. There can be volcanoes in other places as well, and these are known as hot spots – this is what drives Hawaii’s volcanoes. Hot spots are fed by a very hot mantle layer (on which the earth’s crust rests) which bubbles up to the crust and is released. On Earth, plate tectonics keeps the crust moving above the hotspot, which is why there is a chain of islands in Hawaii, not a giant mountain. However, the highest volcano in the solar system is not on Earth. It’s Olympus Mons on Mars. 25 kilometers high and 624 kilometers in diameter, more than twice the size of Tasmania, it is a gigantic shield volcano that is no longer active. Cliffs 6 kilometers high surround the volcano, making it even more imposing on the Martian landscape. It is believed that Olympus Mons was formed by a gigantic hotspot. But since Mars does not have plate tectonics, it was able to grow to its massive size without interruption. Instead of a bunch of smaller ones like Hawaii. If we want to find even more exotic types of volcanoes, we have to look beyond the asteroid belt. Although giant planets don’t have volcanoes, their moons do, but not the ones we’re used to. Io, the moon closest to Jupiter, is the most geologically active object in the solar system, and its volcanoes are rocky and contain a lot of sulfur, creating its characteristic yellow color. Io’s volcanoes are not caused by tectonic plates and heat from the core like Earth. It is caused by the warming of the tides. As Io is very close to Jupiter and orbiting so quickly, Io is greatly affected by Jupiter’s gravity. This means that when Io is in orbit, the whole thing is pushed and pulled by the gravity of Jupiter, which makes its interior hot. Another moon with interesting volcanoes is Saturn’s largest moon, Titan, generally known for its thick nitrogen atmosphere and liquid lakes and oceans on the surface. While Titan’s lakes and oceans aren’t made of water – they’re made of methane and ethane – her volcanoes are made of water. Titan has what’s called cryovolcanism, which means that instead of its volcanoes spewing out molten lava, they spit out water, ammonia, methane, and similar substances. Cryovolcanoes are important to our understanding of the structure of many moons around the giant planet, and that under their hard, icy shells they could have oceans of liquid water.