Volcanoes reveal locations where Earth's internal heat escapes to the surface of the planet. Volcanic eruptions, lava flows, and hydrothermal activity such as geysers are all evidence of Earth's internal heat being released. Regions without volcanic activity keep heat inside the planet.

  !   Click the button to show locations of selected active and dormant volcanoes.

What do you notice about the pattern formed by volcanoes? Are they spread randomly across the globe or do they occur more in some areas than others? Why do some areas show a long line of volcanoes?

1. Hypothesize about why volcanoes form linear patterns across the globe. What does this pattern tell you about Earth's outer shell, or crust?