Chapter 17

Iron

Minerals containing this act like small compass needles and record the orientation of Earth's magnetic field at the time of their formation.

Magnetic field data

Not used by Alfred Wegener to support his hypothesis of continental drift

Magnetic reversal

Occurs and the magnetic field reverses direction

Basalt

Oceanic crust is made mostly of this

Subduction zones

Feature that forms when 2 oceanic plates converge

new ocean crust

Each cycle of spreading and magma intrusion along an ocean ridge results in the formation of this.

The oldest ocean floor is 3.8 billion years old.

False, 180 million

Earthquake Activity and volcano is him are common along sediments.

False, ocean ridges

The study of the magnetic record preserved in Earth's rocks is called ocean ridges.

False, paleomagnetism

The theory of continental draft states that new ocean crust is formed at ocean ridges and destroyed at deep-sea trenches.

False, sea floor spreading.

Magma is formed downward toward the crust.

False, upward

Mountain range

Feature associated with continental-continental plate boundary

rift valley

Results from divergence of continental crust

Isochron

This type of line connects points on a map that have the same age

Rock samples taken near ocean ridges are younger than rock samples taken near deep-sea trenches.

True

Sonar uses sound waves to measure water depth.

True

The Theory of seafloor spreading explains the earth continents move because they ride a thought ocean crust as it moves away from ocean ridges

True

Ocean ridges

Vast, underwater mountain chains

geomagnetic time scale

Was constructed from data gathered from continental basalt flowers

Magnetometer

a device that can detect small changes in magnetic fields