Fast Changes to the Earth

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Fast Changes to the Earths Surface

• 3.7B

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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!

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Why does the Earth quake?
Earth has many layers. The outer layer is called
the crust. It includes the land and the ocean
bottom.
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The crust is broken up into huge pieces of rocks
called plates. These plates are always moving.
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Faults
Cracks in the Earths 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 Earths crust starts to
shake.
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Earthquakes also happen when one plate sinks
beneath another one, or when plates crash or
grind past each other.
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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.

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Ring of Fire

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

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New Madrid Fault System

• In 1811 and 1812, three very strong earthquakes
  struck near New Madrid, Missouri.
• These earthquakes changed the Earths 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.

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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.
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• Scientists are working hard now to make better
  warning systems so that this kind of catastrophe
  wont happen again.

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Volcanoes

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

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• Below Earths 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.