What is an active volcano?
The term “active volcano” is used mainly in reference to Earth’s volcanoes. Active volcanoes are ones that are currently erupting or that have erupted at some time in human history. This definition works well for volcanoes on Earth because we can observe them easily. However, beyond Earth our abilities to detect volcanic eruptions did not begin until the invention of powerful telescopes. Today a number of telescopes are available to detect these eruptions – if they are large enough. However small eruptions would not be noticed and there are not enough telescopes to watch all areas of the solar system where a volcanic activity might occur. Although only a few extraterrestrial eruptions have been detected, much has been learned about them. Perhaps the most important discovery is the ones that have been observed so far are very different from volcanoes that occur on Earth. They are cryovolcanoes.
