Transcript Fast Changes to the Earth`s Surface

Fast Changes to the Earth’s Surface
3.7B
Introduction
The force of an exploding
volcano is awesome. Superhot 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. 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.
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.
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.