Earth Science Ch 17 Assessment

Approximately how long did the Gauss epoch last?

1 million years

Magnetometer

A device that can detect small changes in magnetic fields.

Transform boundary

A region where two plates slide horizontally past each other.

Ridge push

As the older portion of the seafloor sinks, the weight of the uplifted ridge is thought to push the oceanic plate toward the trench formed at the subduction zone in a process called ridge push.

Why was the theory of continental drift not accepted early on?

Because there was no explanation for how the continents moved or what caused their motion.

How fast do plates move relative to each other?

Centimeters per year

What is Wegener's hypothesis called?

Continental Drift

Which is a convergent boundary that does NOT have a subduction zone?

Continental to Continental

What does divergent boundary and transform boundary have in common?

Divergent plate boundaries - plates move apart Convergent boundaries - plates come together Transform boundaries - plates slide horizontally past each other.

Continental Drift

Idea made by German scientist, Alfred Wegener that the Earth's continents had once been joined as a single landmass that book apart and sent the continents adrift.

Which observation was NOT instrumental in formulating the hypothesis of seafloor spreading?

Identifying the location of glacial deposits

Which epoch saw the most fluctuations between normal and reverse polarity?

Matuyama

What is the name that he called this super continent?

Pangaea

Divergent boundaries

Regions where two tectonic plates are moving apart

Which suggested to early cartographers that the continents were once joined?

Shape of the continents

The weight of a subducting plate helps pull it into a subduction zone in which process?

Slab pull

What observations led to the proposal of continental drift?

The matching coastlines of continents of opposite sides of the Atlantic Ocean suggest that the continents were once joined.

Which is NOT a force causing plates to move?

Volcanism

Rift Valley

When continental crust begins to separate, the stretched crust forms a long, narrow depression called a rift valley.

What are the differences between continental-continental convergent boundaries and oceanic-oceanic convergent boundaries?

When oceanic late collides with continental plate, the oceanic plate is subducted under the continental plate. The subducted oceanic plate causes volcanoes and mountain building in the continental plate. When ocean plate converges with ocean plate, one rides up over the other. Which plate ends up on top depends on circumstance.

Subduction

When two plates collide, the denser plate eventually descends below the other, less dense plate in a process called subduction.

Why was the idea of moving continents more widely accepted after seafloor spreading was proposed?

While Wegener collected a lot of data to support the idea that the continents were drifting across the Earth's surface, he could not explain what caused the landmasses to move or how they moved. Seafloor spreading was the missing link. Continents are NOT pushing through ocean crust as he thought but continents are more like passengers that ride along while the ocean crust slowly moves away from ocean ridges.

Generally, what is the age of oceanic crust?

Younger than the continental crust

Seafloor Spreading

is the theory that explains how new ocean crust is formed at ocean ridges and destroyed at deep sea trenches.

What process creates deep sea trenches?

subduction

Techtonic plates

are huge pieces of crust and rigid upper mantle that fit together at their edges to cover Earth's surface.

As shown, which direction does the icy water move?

down

Magnetic Reversal

happens when the flow in the outer core changes and Earth's magnetic field changes direction.

Isochron

is an imaginary line on a map that shows points that have the same age - they formed at the same time.

Which is modeled by the water movement?

mantel convection

Paleomagnetism

the study of the history of Earth's magnetic field

Slab pull

the weight of a subjecting plate pulls the trailing slab into the subduction zone much like a table cloth slipping off the table can pull articles off of it. This also determines the movement of tectonic plates.

Convergent boundaries

two tectonic plates are moving toward each other. There are 3 types of Convergent boundaries. 1. Oceanic-Oceanic 2. Oceanic - continental 3. Continental- Continental