U2L4: Plate Tectonics
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What does the distribution of fossils like Cynognathus on South America and Africa show?
That the continents were once joined together.
How do mountain chains like the Atlas Mountains and Appalachian Mountains support continental drift?
They match in age and structure, showing the landmasses were once connected.
Who first proposed the hypothesis of continental drift in the early 1900s?
Alfred Wegener.
What is the main idea of the Pangaea hypothesis?
All continents were once part of a single supercontinent that later broke apart.
A tectonic plate rides on top of which Earth layer?
The asthenosphere.
What drives tectonic plate movement?
Convection currents in the mantle.
What are convection currents?
Circulating movements of hotter, less dense material rising and cooler, denser material sinking.
In which layer do convection currents occur?
The mantle.
What is slab pull?
When a dense oceanic plate sinks into the mantle, pulling the rest of the plate with it.
What feature divides the sea floor and creates new ocean crust?
Mid-ocean ridges.
What evidence for sea-floor spreading is found in magnetic minerals?
Symmetrical magnetic striping that records magnetic reversals.
What is NOT true about magnetic reversals?
That minerals always align with today’s magnetic poles.
How does the age of seafloor rock relate to its distance from a mid-ocean ridge?
Rock gets older the farther it is from the ridge.
What landform forms where an oceanic plate sinks under a continental plate?
A volcanic mountain range.
How is plate tectonic theory beneficial to society?
It helps predict and prepare for earthquakes and volcanic eruptions.
What is ridge push?
When new, hot rock at a mid-ocean ridge sits higher and gravity pushes the plate outward as it cools and slides away.