A volcano hotspot is a region on the Earth’s surface that has experienced volcanism for a long time. A good example of this is the Hawaiian Islands. Each of the islands in the long chain were created by the same volcano hot spot. The volcano built up an island that extended above the surface of the ocean, and then plate tectonics carried the island away, creating an extinct volcano. But there’s always a new volcano being created by the same hot spot.
There are dozens of volcano hot spots around the world, with the Hawaiian Island chain just being the most well known. Others include the Azores hotspot, the Canary hotspot and the East Australia.
About 30 km below the surface of the Earth is the mantle, a region where temperatures can reach thousands of degrees Celsius. But that’s under the continents. Underneath the oceans, the mantle is only 10 km down or less. Molten rock can seep out of the mantle and form vast magma chambers beneath the Earth’s crust. This magma finds its way to the surface, creating volcanoes.
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Geologists believe that volcano hotspots are created when a narrow stream of hot mantle convects up from the Earth’s core-mantle boundary. This stream is known as a mantle plume.
Another theory is that hotspots are created when asteroids impact the Earth. The shockwave of the impact causes seismic waves to ripple through the Earth and create a hotspot on the exact opposite point on the Earth from the impact. This is known as the antipodal pair impact theory.
One of the most dramatic volcano hotspots wasn’t here on Earth but on Mars; the hotspot that created the largest volcano in the Solar System – Olympus Mons. Scientists believe that plate tectonics ceased on Mars billions of years ago, but the same volcanic hotspot kept pushing up magma. This allowed Olympus Mons to continue growing for billions of years, and reach its current height of 27 km.
We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.