Continental Drift
What was the name of the giant supercontinent that existed millions of years ago?
Pangaea
What are the vibrations caused by earthquakes called?
Seismic waves.
What technology uses sound waves to map the ocean floor?
Sonar
About how fast do Earth's tectonic plates move each year?
1–3 centimeters per year.
What type of plate boundary occurs when two tectonic plates move AWAY from each other?
Divergent boundary.
Which scientist proposed the hypothesis of continental drift in 1912?
Alfred Wegener
What instrument do scientists use to record and measure seismic waves?
A seismograph.
What is the name of the underwater mountain chain where new ocean floor forms?
Mid-ocean ridge
What is the process called when one tectonic plate sinks beneath another plate and into the mantle?
Subduction.
What type of plate boundary occurs when two tectonic plates COLLIDE?
Convergent boundary.
Name TWO pieces of evidence Wegener used to support continental drift.
Any two: matching fossils, matching rocks and mountains, matching coastlines, or evidence of past climates.
What TWO parts of Earth combine to form the lithosphere?
Earth's crust and the rigid uppermost part of the mantle.
Where would scientists find the OLDEST rocks on the ocean floor?
Farther away from the mid-ocean ridge.
Name the THREE processes that help drive tectonic plate movement.
Convection in the mantle, seafloor spreading, and subduction.
What type of plate boundary is responsible for earthquakes along the San Andreas Fault?
Transform boundary.
Why did many scientists originally reject Wegener's continental drift hypothesis?
He could not explain what caused the continents to move.
Scientists discovered that Earth's crust is not the same everywhere. What are the TWO types of crust, and which one is thicker?
Continental crust and oceanic crust. Continental crust is thicker.
What happens to magma when it rises at a mid-ocean ridge?
It cools and hardens, forming new ocean floor.
During convection in the mantle, what happens to hot material and cool material?
Hot material becomes less dense and rises. Cool material becomes more dense and sinks.
What TWO landforms can form when tectonic plates collide at a convergent boundary?
Mountain ranges and deep-ocean trenches.
Scientists found identical fossils on continents separated by oceans. Explain how this evidence supports continental drift.
The continents were once connected, allowing the same organisms to live in those areas before the continents slowly moved apart.
Why do seismic waves change speed and direction as they travel through Earth?
Because they travel through different materials and rock layers with different densities.
Scientists discovered that ocean-floor rocks become older as you move farther away from a mid-ocean ridge. What process does this evidence support?
Seafloor spreading.
Why does Earth's surface not keep getting bigger even though new oceanic crust is constantly forming?
Old oceanic crust is recycled back into the mantle through subduction as new crust forms at mid-ocean ridges.
At a divergent boundary, tectonic plates move apart. Explain what happens between the plates and what new feature forms.
Magma rises between the plates, cools, and hardens to form new oceanic crust at a mid-ocean ridge.