Transcript plates - Perry Local Schools

• What do you think these continents looked
like 200 million years ago?
• Back in the 1900s, Alfred Wegener,
german scientist, noticed that Earth’s
continents looked like pieces of a puzzle.
When he put them together they seemed
to form one large continent. He named
this continent PANGEA
Alfred Wagener is credited with the theory of continental drift.
What two other reasons did they use to say that
the continents were all once connected, besides
they look like puzzle pieces.
Plate Tectonics
• The world is
made up of a
bunch of ‘plates’
that move over
time in different
directions and at
different rates.
Lithosphere-includes the crust and part of the mantle,
this is what is divided into the tectonic plates.
Asthenosphere- the layer under the lithosphere which
allows the plates to slide, made up of mantle.
• They glide across the Earth much like ice
drifts across a pond.
• Geological activity that happens on the
Earth’s surface happens at the boundary
between the plates.
What do I mean by geological activity?
• Most are located with
oceanic crust
• Earthquakes and Tsunamis
are caused by this type.
• Lithosphere is pulled apart,
as this happens the block
between the two pulling
surfaces cracks and falls
allowing magma to seep up
to the surface.
• Two plates slide past one
another, lack large
surface features.
• Most famous is San
Andreas Fault in
California. Unlike popular
belief California will not
fall off into the
ocean…however, Los
Angeles will eventually be
located beside San
Francisco!
• Sliding plates cause lots
of earthquakes and
sometimes Tsunamis!
• Places where plates
crash or crunch together
are called convergent
boundaries
• Take a look at the edge of
the plates…the
continental plate has
folded into a huge
mountain range while the
oceanic plate is digging
deep into the ground.
• Earthquakes, mountains,
Tsunamis and volcanoes
are also caused by this
type of boundary!
Mountains
• Formed when two plates
push against one another,
at a convergent plate
boundary, the crust
becomes thicker and
begins moving upward.
• Some Mountains are still
growing (Mt. Everest) while
others are slowly eroding
away.
Appalachian Mountains
Rocky Mountains
Tsunami
• a series of water waves caused by the
displacement of a large volume of water
by an earthquake, volcanic eruption, or an
undersea landslide.
How Tsunami’s Become
Destructive
http://www.pbs.org/wgbh/nova/earth/anatom
y-tsunami.html
• They occur mostly at the boundaries of
tectonic plates
• Fault- a break in the Earth’s crust where
the crust slide against one another.
• Earthquakes- vibrations of the Earth’s
crust caused by slippage along a fault
• As plates move their edges experience
immense pressure and the rocks
eventually break.
• Earthquakes happen all of the time, most are so
small that we don’t even feel them.
• Tremors- refers to the shaking that is felt with an
earthquake
• Seismology is the study of earthquakes!
– The Richter scale is used to measure the amount of
energy released by an earthquake, called
magnitude.
– magnitude 2 or lower earthquakes we rarely ever
even feel them
– magnitude 7 and over causing serious damage over
large areas.
– Largest magnitude ever recorded was a magnitude
9.5!
Earthquake Hazard
• Scientists still cannot predict when
earthquakes will take place.
• We do know where they are most likely to
occur.
Turn to page 94 in your book!
Earthquake Proof Areas
-Looking at the highest hazard level areas in the
United States, we can help people prepare for
the possibility of Earth quakes.
-Areas prone to Earth quakes, they build buildings,
bridges, homes that are at least partially
earthquake resistant.
-these buildings are usually slightly flexible so
that they can sway with the ground motion.
All About Volcanoes
• Volcano- a mountain built from magma
(melted rock) that rises from the Earth’s
interior to its surface.
• Usually located near tectonic plate
boundaries
• Located on land and in the ocean.
– Volcanoes create islands!
• Most active volcanoes are located in the
Pacific Ocean on the ‘ring of fire’.
RING OF FIRE
• Contains 75% of the world’s active
volcanoes
• Located right on a plate boundary.
• There are many different types of
Volcanoes believe it or not.
– Composite Volcanoes have layered ash,
cinders and lava (Mt. St. Helens, Mount
Rainier)
– Cinder cones are the smallest and most
abundant. Violent eruptions occur and usually
only last for a short time
Volcanoes can come in many shapes and sizes.
Effects of Volcanic Eruptions
• Volcanoes erupt when the pressure of the
magma inside builds up and can not be
contained inside any longer.
• Clouds of hot ash, dust, and gases can flow
down the slope of a volcano at speeds up to
4,400miles/hour!
• They can completely devastate an entire city in
split seconds.
• Major volcanic eruptions can change Earth’s
climate for years!
– Ash and gases reduce the amount of sunlight that
reaches the Earth’s surface
– Can cause drops in temperature world wide
• The forces at the boundaries of plate tectonics shift
rocks around, bringing some to the surface and
sending others below.
• Weathering- the breaking down of Earth’s rocks by
natural processes
• Erosion- the removal and transport of surface materials
– Water and wind erosion are the two most common ways to
remove and transport materials.
– Remember Rocky Mountains vs. Appalachian Mountains!