Why Do Volcanoes Erupt

Deep beneath the Earth's surface, it is incredibly hot. Rock melts into a thick, glowing liquid called magma. When pressure builds up, the magma pushes through cracks in the Earth's crust. When magma reaches the surface, it is called lava. This is a volcanic eruption.

What Causes an Eruption

Magma forms deep underground where temperatures are high enough to melt rock. This liquid rock is lighter than the solid rock around it, so it rises. As magma moves up, gases inside it start to expand. The pressure builds like shaking a soda bottle. When the pressure gets too great, the volcano erupts.

Different Types of Eruptions

Not all eruptions are the same. Some volcanoes ooze lava slowly and gently. Hawaiian volcanoes often erupt this way. Other volcanoes explode violently, shooting ash and rock high into the air. Mount St. Helens erupted explosively in 1980. The type of eruption depends on the thickness of the magma and the amount of gas.

Fun Facts

• The loudest sound in recorded history was the eruption of Krakatoa in 1883, heard nearly 3,000 miles away.
• Volcanic ash can travel around the entire globe and affect weather worldwide.
• Some volcanic eruptions produce lightning inside the ash cloud.

Did You Know?

The word volcano comes from Vulcan, the Roman god of fire. The Romans believed that Vulcan had his forge under the volcanic island of Vulcano near Sicily!