Landscapes and Landforms

Some mountains are made of solid rock, like the Rocky Mountains or the Swiss Alps. But, some mountains are actually volcanoes.

Volcanoes have existed for a long time on Earth, likely causing disasters such as the Permian mass extinction about 250 million years ago, the greatest mass extinction in Earth's history, according to a 2015 paper. Volcanoes can and have existed on other worlds as well: although volcanoes on the moon and Mars have long been dormant, volcanoes are still very active on Jupiter's moon Io. Researchers are currently striving to find ways to predict when volcanic eruptions might happen on Earth by analyzing clues such as crystals and gases linked with volcanoes.

Volcanoes can have many different appearances. Some volcanoes are perfect cone shapes while others are deep depressions filled with water. The shape of a volcano provides clues to the type and size of eruption that occurred. Eruption types and sizes depend on what the magma is made up of.

This section looks at the relationship between plate tectonics, earthquakes and volcanoes, which helps to explain how volcanoes form.