Plate tectonics test March 2023

Convergent Boundary

Plates colliding

Divergent Boundary

Plates separating

Transform Boundary

Plates sliding past each other

Convergent boundaries create . . .

Mountains

Divergent boundaries create . . .

Trenches

Magnetic polarity

The north and south poles of the earth switch every 300,000 years

Continental drift

The theory that continents have moved towards and away from each other as they are pushed by the mantle.

Seafloor spreading

The growing of oceanic crust at divergent boundaires wehn magma comes up through the separation in the crust, then comes up and hardens creates new crust, causing the seafloor to spread.

Where does old crust turn back into magma?

At convergent plates/ subduction zones.

Oceanic crust is made of . . .

Basalt + Iron

Continental crust is made of . . .

Granite + Silica

Divergent boundary is also called :

Constructive boundary

Because new crust is constructed there

What was Wegner’s evidence of continental drift?

The continents fit together like a puzzle

Similar fossils and rocks were found on separate continents.

The earth’s “giant conveyor belt” is

Convection currents

Most earth quakes and volcanoes happen on the . . .

Pacific ring of fire

Oldest rocks are found _______ a ridge

furthest from

Newer rocks are found _______ a ridge

closer to

Who was Alfred Wegner ?

The German scientist who was first to bring up the theory of continental drift.

Earths plates are moving in ______ motion

Slow

How much do plates move per year?

2\.5 -15 cm per year

Lithosphere -

The hard outside part of the earth

The plates of the earth

Crust + Upper solid mantle

Asthenosphere -

Beneath lithosphere

Pushes the plates (lithosphere)

The mantle

This is where convection currents are

What creates the convection currents?

Heat from the earth’s core

How does the earth’s core produce heat?

Nuclear reactions

Continental Crust : _________ dense

Oceanic Crust : __________ dense

less

more

Earth’s magnetic feild -

N and S poles

Core is a big magnet

Two circling motions around earth

Define: convection currents

The movement of heat through a liquid or gas causing heat to rise and cool to sink, making a circular motion.

What type of stress is at a convergent boundary?

Compression

What type of stress is at a divergent boundary?

Tension

What type of stress is at a transform boundary?

Shearing

Subduction zone -

A convergent boundary where one plate was denser that the other, causing it to subside, or sink beneath the less dense one into the mantle.

Ways volcanoes can occur:

1. Magma rises to surface at divergent zone
2. A subduction zone allows magma to rise
3. At a hot spot (hole in crust)

Holes in earth’s plates are called :

Dedetachments