Earth's Layers
This is the thinnest layer of the Earth, measuring 5–70 km thick.
What is the crust?
Alfred Wegener proposed this theory, suggesting all continents were once a single landmass.
What is Continental Drift?
This type of boundary occurs where plates move apart, mostly found in the ocean.
What is a divergent boundary?
These underwater mountain ranges appear in every ocean and are where seafloor spreading begins.
What are mid-ocean ridges?
These deep canyons form in the ocean floor where a plate sinks in a subduction zone.
What are deep-ocean trenches?
This layer of the Earth is a liquid mass made of iron and nickel.
What is the outer core?
This Greek name, meaning 'all lands', refers to the giant supercontinent that existed 200 million years ago.
What is Pangaea?
At this boundary type, plates push together, resulting in the folding or destruction of crust.
What is a convergent boundary?
This process adds new material to the ocean floor as molten rock rises through cracks in the ridge.
What is seafloor spreading?
These are formed when two plates carrying continental crust collide and crumple upward.
What are mountains (or mountain ranges)?
It is the thickest layer of the Earth, measuring about 2900 km thick.
What is the mantle?
Wegener used these as evidence, such as the Mesosaurus found in both South America and Africa.
What are fossils?
This boundary occurs where plates scrape past each other horizontally.
What is a transform boundary?
Scientists found that these 'flips' in Earth's magnetic field are recorded in stripes on the seafloor.
What are magnetic reversals?
This feature forms at a divergent boundary on land as a continent begins to split apart.
What is a rift valley?
This layer is made of the crust and the very top of the mantle.
What is the lithosphere?
This type of evidence for drift involves matching rock layers in the Appalachians to those in Scotland.
What is geology (or rock evidence)?
This specific process occurs at a convergent boundary when one plate sinks beneath another.
What is subduction?
Rocks found here are the youngest on the seafloor.
What is the spreading center (or mid-ocean ridge)?
These chains of volcanic islands form on the top plate in an oceanic-oceanic subduction zone.
What are island arcs?
This layer of hot, soft rock in the upper part of the middle mantle allows the tectonic plates to move.
What is the asthenosphere?
These are the three main pieces of evidence Wegener used to support his theory.
What are fossils, climate, and geology?
This famous California fault line is an example of a transform plate boundary.
What is the San Andreas Fault?
These plumes of heated rock rising from the mantle can be used to track plate movement.
What are hot spots?
This specific type of mountain range, like the Cascades, forms as oceanic crust sinks under a continent.
What are coastal mountains?