1. Continental Drift
Alfred Wegener thought of the theory of continental drift-that the continents move.
250 million years ago all the continents were connected as only one continent called Pangaea.
His reasons were:
The same types of rock were on different continents
The shapes of the continents “fit together”
The same types of fossils were on different continents
180 million years ago Pangaea broke in two pieces, Gondwanaland and Laurasia
Geologists think that convection currents in the mantle move large sections of the Earth’s crust, called plates.
The plates are still moving!

2. The Plates of the Earth North American Plate South American Plate
African Plate
Eurasian Plate
Pacific Plate
Indo-Australian Plate
Antarctic Plate
Nazca Plate

3. Boundaries
Plates move ___________________________ at transform boundaries.
Plates move ___________________________ at divergent boundaries.
Plates move ___________________________ at convergent boundaries.
Transform Boundaries
frequently cause ___________
no new crust formed, __________ old crust recycled
moves about 2 in (5 cm) per year on average
example: ________________
Divergent Boundaries
plates move _______________each other
examples: the Mid-___________ Ridge, Iceland, the African Rift Valley
lava forms new crust and __________ the older crust away.
underwater this is called sea-floor _____________
the newest crust is _____________________
most ______________ are at divergent boundaries

4. Boundaries p.2 Convergent Boundaries
Plates move towards each other and ________
Examples: Ring of Fire, Andes Mtns., Aleutian Islands, Himalayan Mtns.
many mountains, volcanoes and ___________ happen at convergent boundaries
old crust is ________ and recycled
Could be continent vs. continent
pushes up tall __________________ parallel to boundary, like Himalayan Mountains with Mt. Everest
Could be oceanic vs. (continent or oceanic)
oceanic plates are ___________ and heavier than continental plates
subduction occurs when the oceanic plate slides _______________ the other plate and melts in mantle.
forms a deep trench, example: _____________ Trench in Pacific Ocean or arcs of ____________________ that are parallel to boundary
makes lots of cracks in upper plate, which fill with ______________ making ___________________

5. Earthquakes
happen at faults (cracks in the crust), not just at transform boundaries
Faults are in tension (being pulled), until they move and vibrate
Seismic waves carry those energy from those vibrations in 3 directions
P waves go front to back, fastest speed
S waves go side to side
Surface waves go up and down, slowest speed
The focus is where the earthquake starts underground.
The epicenter is directly above the focus on the surface.
A seismometer is a device that prints a picture of the vibrations called a seismograph.
The magnitude (strength) of an earthquake is measured on the Richter scale.
NO ONE CAN PREDICT AN EARTHQUAKE!