There is plenty of hot stuff in our solar system, even in the outer frozen realms. Planetary scientists have found evidence of volcanism on every terrestrial planet, on many of the moons and even some asteroids!
The Moon and Mercury have thick volcanic flows on their surfaces, erupted long ago from fissures in their crusts. While the Moon and Mercury have relatively small volcanoes, those on Venus, Earth and Mars are large and numerous. We know that Earth's volcanoes are still active and Venus' may be, but scientists debate whether Mars' volcanic activity has finished. Jupiter's moon Io holds the record for the most volcanically active body in the solar system (other moons feature a colder form of volcanism -- cryovolcanism; learn more about cryovolcanism under our topic, Ice in the Solar System).
Volcanologists on Earth have applied their knowledge to these other places in our solar system. Volcanic activity acts as a window to a planet's interior. The type of volcanism and the composition of the lava give scientists a peak underneath the crust. The very presence of volcanic features tells scientists that a planet's interior is -- or was -- hot enough to form magma that erupted at its surface.
Startling results from Venus Express and MESSENGER's mission to Mercury are redefining our understanding of planetary history: instruments aboard Venus Express suggest recently active volcanoes and MESSENGER shows widespread lava flows occurring long after Mercury formed.
Volcanoes can have a profound effect on people. Eruptions can disrupt air traffic, as we experienced in the 2010 Iceland eruptions. Numerous examples exist in history where thousands of people died as clouds of ash, lava and mud flows buried villages and cities. Volcanoes can impact the entire Earth's climate: the eruption of Mount Pinatubo in the Philippines in 1991 caused a global cooling of one degree over the next year. But eruptions also have a role in creation; in addition to new land, volcanic activity helps to create a planet's atmosphere. Volcanic eruptions on early Earth spewed gases from the interior. (This outgassing continues today.) Most of the gas was carbon dioxide and water vapor. It was modified over time through chemical reactions with rocks and photosynthesizing organisms.
This topic's Classrooms and Organizations & Clubs sections have a variety of activities on volcanism! Examine this topic to investigate volcanism on Earth and throughout the solar system.