Studied by 6 people
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:
Magma rises to surface at divergent zone
A subduction zone allows magma to rise
At a hot spot (hole in crust)
Holes in earth’s plates are called :
Dedetachments
Note 
Flashcard (50)