Structure of Earth
Drifting Continents
Seafloor Spreading
Plate Tectonics I
Plate Tectonics II

100

The thin, rigid outer layer of Earth that includes the surface.
What is the crust?

100

The name of the supercontinent formed by the combining of Earth’s landmasses.
What is Pangaea?

100

A long narrow chain of ?mountains that runs along the ?Atlantic Ocean floor.
What is the Mid-Atlantic Ridge?

100

A slab of lithosphere that moves on Earth’s surface.
What is a plate?

100

These flows of energy in the upper mantle may cause plate motion.
What are convection currents?

200

The thickest layer of Earth, ?mostly solid.
What is the mantle?

200

Evidence that continents were combined includes the puzzle-like fit of Africa and this continent.
What is South America?

200

The deepest regions of ?the ocean floor.
What are trenches?

200

A place where two plates are moving toward each other.
What is convergent ?plate boundary?

200

Hot mantle material rises because of this property compared to its surroundings.
What is lower density?

300

The part of Earth’s center that is composed of liquid iron and nickel.
What is outer core?

300

Evidence that continents were combined includes signs of once living things called this.
What is a fossil?

300

Compared with rocks near ?the trenches, rocks near the ?ocean ridges are this.
What is younger?

300

A place where two plates are moving away from each other.
What is divergent plate boundary?

300

A force that pushes an oceanic plate toward a trench.
What is ridge push?

400

The crust and the uppermost part of the mantle that is rigid.
What is the lithosphere?

400

A scientist who proposed the hypothesis of continental drift.
Who is Alfred Wegener?

400

This is formed at ocean ridges.
What is ocean crust?

400

A place where two plates are sliding past each other.
What is a transform plate boundary?

400

A force in which the weight of a subducting plate pulls on the rest of the plate.
What is slab pull?

500

The slushy layer of the upper mantle upon which the lithosphere floats.
What is the asthenosphere?

500

The hypothesis of continental drift was rejected for a long time because it could not explain this.
What is the mechanism for plate movement?

500

Rocks on the ocean floor show reversals in the polarity of this over geologic time.
What is Earth’s magnetic field?

500

The process of one plate descending beneath the other.
What is subduction?

500

The name of a valley in East Africa where two plates are spreading.
What is The Great Rift Valley?