Download Continental Drift - Ms. Mosley

Warm-Up
• Grab your mastery folder and the papers from the back table.
• Begin figuring out your level of mastery from the pre-test
using your test answer sheet and the mastery paper (on the
back table).
• Some students received partial credit on a question. You will just
turn the percentage into a decimal. So if you earned a 70% on a
question, that is a .7 that you will use to divide by the total
number of questions.
• There are calculators on the small group table if you need a
calculator.
• SWBAT explain the physical processes associated with tectonic
plate movement
Continental Drift
& Plate Tectonics
Geology
Rocks!
NAME___________________________
Alfred Wegener (Weg-en-er) was a meteorologist and explorer. In 1912, he came
up with the idea that the continents did not always look like they do today.
1
Rocks
Climate
Fossils
Wegener’s idea came from studying
____________ , _______________ , and the
___________________ of all of today’s
continents. He found that the fossils and
mountains in South Africa matched the fossils
and mountains in Argentina. How could that
be? There is an ocean between South Africa
and Argentina!
He also found fossils of tropical plants in places
like Greenland. How could a tropical plant live
in snowy Greenland!?
2
Pangaea – 200 Million Years Ago
Seven Continents - Today
The mystery was puzzling. That’s when Wegener came up with the theory that the
continents did not always look like they look today. He said that they used to be one big
supercontinent. He named this large continent Pangaea. Pangaea is a Greek word that
means “all lands.”
3
Wegener said that it took millions of years for the seven continents
we know today to drift to where they are now. But, he did not
know how the continents drifted. Continents are huge! How
could a big, heavy continent move that far?
Because Wegener could not prove his theory, other scientists did
not believe him. He had some evidence, but he needed to figure
out how the continents moved if he was going to get others to
believe his theory.
4
Wegener never figured out how the continents moved, but his work led the way for
other scientists. These scientists used new technology to collect information. They
measured the ocean floor, recorded earthquakes, and studied the Earth’s magnetic
fields. They used the things they learned to form a theory on how continents could
move. This new theory was called plate tectonics. The theory of plate tectonics
explains how the Earth’s plates move and change.
The Earth is made of layers, very much like an egg. The top layer of the Earth is called
the crust. The theory of plate tectonics says that the top layer of the Earth is broken up
into many plates, or thin sections, that move and change.
5
plates
super-heated rock
Under the plates, there is another layer of rock called the mantle. The mantle has two
parts. The first part is a rock layer. The second part is made of super-heated rock. The
plates float on this super-heated rock, but they don’t float like rafts float in a swimming
pool. The melted rock is very thick like silly putty. So, the plates drift very slowly.
6
In 50 to 100 million
years, the Earth could
look like this!
Scientists believe the Earth’s continents have divided and drifted back together many
times in Earth’s history. Although you cannot see it with your eyes, the plates are still
moving today. It can take a whole year for a plate to move just a few centimeters. That
means that in your whole lifetime, our continent will only move about 2 feet. However,
in millions of years, the Earth will look very different than it does today.
7
What is Plate Tectonics?
• Plate tectonics is the theory that explains the formation,
movement and subduction of Earth’s plates
What happens when the plates
move?
• No plate can budge without affecting the other plates
surrounding it.
• As the plates move, they collide pull apart, or grind past each
other producing changes in the Earth’s surface.
What kind of Changes?
Volcanoes!
Mountain ranges!
Earthquakes!
Sea-trenches!
Plate Boundaries
• The edges of the different plates meet at lines called Plate
Boundaries
• At the border of plate boundaries are FAULTS—cracks in the
Earth’s crust
• There are three different types of boundaries that occur
because of their different movement
Types of Boundaries
• Transform Boundaries
• Divergent Boundaries
• Convergent Boundaries
Transform Boundaries
• Along transform
boundaries crust isn’t
created or destroyed
• At a transform
boundary the two
plates slip past each
other
Transform Boundaries
• Why do earthquakes shake California?
• The state straddles two plates that are moving past each other
like trains on opposite tracks. The plate boundary is marked by a
zone of active faults—breaks in the rock and ground surface
caused by plate movements.
Transform Boundaries
• The most famous of
these is the 1200-km
(750-mi) long San
Andreas Fault. The San
Andreas fault is a
transform fault, a kind
common on the sea
floor but rarely found
on land.
Divergent Boundaries
• The place where two
plates move apart—or
diverge—is called a
divergent boundary
• Most divergent
boundaries occur at the
mid-ocean ridge—so
crust is forming
• When divergent
boundaries occur on land,
a rift valley is formed
Rift valley
Convergent Boundaries
• The place where two
plate boundaries
come together or
converge is called a
convergent
boundary
• A collision is when
two continental
plates hit each
other—the density
of the crust
determines which
plate goes under the
other one
• Ex. – The Himalayan
Mountains
Convergent Boundaries - Subduction
• One tectonic plate sinks
under the other
• Basalt is what oceanic
crust is made out of. It is
more dense than
continental crust. Use
this fact to explain the
movement of these
plates around the
convergent boundary.
• Ex: Japan