2. • Scientists believe that about 250 million
years ago, a supercontinent known as
Pangea existed.
• This supercontinent was made up of all
the continents on Earth.
• Over time, these continents have broken
apart and slowly drifted away from one
another.
What do you think caused the continental plates
to shift? Did they simply swim away from each
other?
3. • Pangea started to form around 540
million years ago and didn’t finish until
the Triassic period 200-250 million years
ago, during the age of dinosaurs.
• Because Pangea was one large continent,
all dinosaurs spread across the land.
• Today, fossils of the same species of
dinosaurs can be found all over the world,
which must mean that Pangea existed!
What force on Earth could possibly have enough
energy to cause the continents to move as far as
they have?
4. • Scientists have been able to measure and map
out the ocean floor with new technology.
• Located in between two continents, they
discovered trails of raised areas, called ridges,
as well as deep trenches.
• Ridges represent areas where new crust is
being formed as hot magma escapes from the
Earth’s core and spreads outward. As the
seafloor spreads outward away from the area
where magma is being released, the continents
are carried across the sea, riding on top of the
crust.
• As new crust is created, older crust submerges back into the mantle, being
melted once again. This occurs at locations where there are deep ocean
trenches where the crust is being lowered back into Earth’s core.
5. As new crust is created in a particular location on Earth, it forms what resembles giant
plates. One side of the plate is where new crust is being created, while the other side is
where older crust is being destroyed. This process is called plate tectonics.
Watch how this process works:
6. Listen to this song parody to help you understand how plate tectonics works.
7. • So we know continents are not just
sitting on water. They are the top
layer of the Earth’s crust.
• But what exactly is under the surface
of our planet?
• The outer most layer is called the
crust, which is brittle and cold and the
only layer exposed to the surface of
the planet.
• The next inner layer is the hot and
convecting mantle layer.
• Finally, the core, which is dense and
metallic, is comprised of two layers,
the outer and inner core.
8. • Plates the size of continents and
oceans move at rates of
centimeters per year in response
to movements in the mantle
• The Earth’s crust, or lithosphere, is
thus divided into different plates that
sit like a puzzle next to each other.
Their boundaries extend deep into the
lithosphere.
• There are three types of plate
boundaries and are differentiated in
the way the plates interact with each
other.
The table above shows the number of
convergent and divergent boundaries
for different plates in Earth’s crust.
10. • A divergent boundary is a place where two tectonic plates are moving
away from each other. As the plates pull apart, the crust stretches. The
thin and weak crust breaks along faults, causing earthquakes.
• These boundaries usually take place at ocean ridges and are zones of
intense volcanic activity
• Divergent boundaries on land create lines of volcanoes.
11. • A convergent boundary is where two plates collide together and one
plate gets forced down beneath the other.
• When this plate boundary occurs on land, it results in the formation of
mountains. A parallel oceanic trench typically forms just off the shore, as
one plate descends deep into Earth’s core.
• Because two plates rub against each other at convergent boundaries,
they commonly cause earthquakes and volcanoes to form.
12. • Where two plate boundaries slide horizontally past each other
• Neither plate is added to at the boundary, nor destroyed.
• When the plates slide sideways past each other and eventually slip,
rocks break, creating massive amounts of energy to build up.
Occasionally this energy is released suddenly in the form of
earthquakes.
13. • The state of California is cut by a
transform plate boundary, and a
convergent boundary sits off-shore in
northern California.
• Most of California is situated on the
North American Plate. A small part of
California, west of the San Andreas
Fault, lies on the adjacent Pacific Plate.
• The San Andreas Fault is a transform
plate boundary. Because the boundary
is not in a straight line, the plates do
not slide smoothly and moves in jerks.
14. • California’s mountains are often
formed from interactions at several
plate boundaries. For example, as
rocks on one side of a transform plate
boundary grind and push against the
rocks on the other plate, mountains
such as the Transverse Ranges, can
form.
• Because of California’s plate
boundaries, it is a place
where many geological
events occur.
• In particular, earthquakes are
very common in California.
15. Plate Tectonics and Earth’s Structure - Guided Notes
Answer the questions below as you follow along with the lecture.
How old is Pangea?
What proves that Pangea once existed?
How did Pangea start to shift?
What do you think caused the continental
plates to shift? Did they simply swim away
from each other?
What force on Earth could possibly have
enough energy to cause the continents to
move as far as they have?
Why are most earthquake zones near plate
boundaries?
How do these movement of tectonic plates
cause earthquakes?
16. Identify: Draw arrows on the figures to identify which
direction the tectonic plates are moving and label the type
of plate boundary is illustrated. Put a star where an
earthquake is likely to happen.
17. Label the parts of Earth’s structure.
Infer: Use the earthquake locations to help you figure out
where the tectonic plate boundaries are. Use a colored
pen or markers to draw plate boundaries on the map.
18. Vocabulary:
• Continental rifting
• Convergent plate boundary
• Divergent plate boundary
• Fault
• Transform plate boundary
Use the vocabulary terms to complete the diagram.
19. Use the map above to answer the following questions.
1. Analyze why many earthquakes, but only a few volcanic eruptions, occur in the Himalayas.
2. Explain the action of the plates along the San Andreas Fault and why volcanos do not form there.
