Volcanoes in the Solar System
Volcanoes in the Solar System fall into two primary categories: dead volcanoes and active ones. Dead volcanoes are found on Venus, Earth and its Moon, and Mars. Active volcanoes are located on Earth, Jupiter's Io, and possibly on Venus, on Saturn's Titan, and on Neptune's Triton. Terrestrial and outer space volcanoes share some common properties. Volcano-producing bodies must have solid surfaces, molten rocks, and some form of heat. The heat process, that drives volcanic activity on Earth, is different from the type that drives volcanism on Io and other planetary satellites. Radioactive decay is the source of heat for volcanoes on Earth and has been since its formation some 4.6 billion years ago. Radioactivity takes place in the Earth's interior producing enough heat to melt rocks (magma). This magma reaches the Earth's surface through vents or openings forming volcanic lava flows. Tidal heating is the source of heat for volcanism for all the volcanic activity in the satellites of the Jovian planets. Whenever a variable gravitational force exists between planets and their satellites (because of orbital eccentricity), and when the rotation and orbital period of the satellite are not synchronized, as the satellites orbit the planet, they are squeezed and flexed. Their cores may become extremely hot, hot enough to melt rocks creating magma which flows to the surface in the form of volcanoes or gaseous plumes.
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