Calderas can be more than 25 kilometers in diameter and several kilometers deep. They can be steep-sided and are often circular.
There can be tectonic activity in calderas, such as earthquakes, uplifts, or ground subsidence. Hot springs, geysers, boiling mud pits, and other signs of geothermal activity are also common in calderas. Caldera activity can be monitored and researched to predict future volcanic eruptions.