Fast Changes to the Earth’s Surface 3.7B

Introduction The force of an exploding volcano is awesome. Super-hot lava shoots out! Smoke, ash, and dust rise high into the air. Volcanoes, earthquakes, big storms and landslides are very powerful forces of nature. They can move mountains, soil, trees, water, and everything else in just seconds!

Why does the Earth quake? Earth has many layers. The outer layer is called the crust. It includes the land and the ocean bottom.

The crust is broken up into huge pieces of rocks called plates The crust is broken up into huge pieces of rocks called plates. These plates are always moving.

Faults Cracks in the Earth’s crust are called faults. When rocks get stuck along a fault, the plates keep moving. If the rocks break or slip, the plates move suddenly, and Earth’s crust starts to shake.

Earthquakes also happen when one plate sinks beneath another one, or when plates crash or grind past each other.

More About Earthquakes Earthquakes happen every day somewhere on Earth. The shape of the land can change where earthquakes occur. But most earthquakes are small and cause no damage.

Ring of Fire The most active earthquake zone in the world is around the Pacific Ocean. California, Hawaii, and Alaska are in this zone.

New Madrid Fault System In 1811 and 1812, three very strong earthquakes struck near New Madrid, Missouri. These earthquakes changed the Earth’s surface more than any other earthquake in American history. Large areas of land sank and new lakes formed. Thousands of acres of forests were destroyed. One quake even changed the course of the mighty Mississippi River.

The morning of December 25, 2004, started out peacefully in South Asia The morning of December 25, 2004, started out peacefully in South Asia. Then a huge earthquake struck deep in the Indian Ocean. The quake caused a tsunami, or giant wave. The tsunami spread across the Indian Ocean for 4,500 kilometers moving at 500 mph. As the wave reached the shore, it slowed down, but grew taller. The first wave was over 9 meters (30 feet) tall when it crashed on shore. When the wall of water slammed onto the coast, property was destroyed and more than 200,000 people died.

Scientists are working hard now to make better warning systems so that this kind of catastrophe won’t happen again.

Volcanoes Most volcanoes look like mountains. A cone forms when materials such as ash, solid rock and lava (melted rock) erupt through the cone.

Below Earth’s crust, red-hot rock, called magma, rises up Below Earth’s crust, red-hot rock, called magma, rises up. Force from below pushes it up toward the surface. A volcano forms when magma and hot gases escape through openings in the surface of the Earth.