Earth's History

Earthquakes happen when stress builds up along faults in Earth's crust and suddenly releases. Seismic waves radiate from the focus, shaking the ground.

Volcanoes form where magma from the mantle reaches Earth's surface. Shield volcanoes have gentle slopes with flowing lava, while composite volcanoes are steep with explosive eruptions.

Sinkholes form when underground limestone dissolves, leaving a cavity that collapses. They are common in areas with karst topography where water slowly dissolves the bedrock.

Tides are the daily rise and fall of ocean water caused mainly by the Moon's gravity pulling on Earth. Most coasts experience two high tides and two low tides each day as Earth rotates.