The Theory Of Plate Tectonics
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Inside Earth, temperatures are about _______ at depths of around 100 km below the surface and can reach _______ in the inner core.
1,000°C , 7,000°C
In spite of these high temperatures, most of the rock inside Earth has not _______ and is in the _______ state.
melted, solid
Melted rock inside Earth is called?
Magma
Who first suggested continental drift?
Alfred Wegener.
When was plate tectonics fully developed?
1950s–1960s, using ocean floor evidence.
Why is plate tectonics important?
It helps explain earthquakes, volcanoes, and mountains.
What is the lithosphere?
Earth’s rigid outer layer (crust + upper mantle).
Where do earthquakes happen?
Plate boundaries.
Which moves faster?
Oceanic plates
How fast do plates move?
A few cm per year.
Where do plates move on?
Asthenosphere
What is a tectonic plate?
A piece of Earth’s crust
How thick are tectonic plates?
Up to about 100 km.
What are plate boundaries?
Places where plates meet.
What happens at plate boundaries?
Earthquakes, volcanoes, and mountains form.
What happens inside plates?
Little geologic activity.
How fast do plates move?
About 2–15 cm per year.
Where do earthquakes happen?
Plate boundaries.
Why do continental plates move slower?
They are heavier and have deep roots.
What did ocean floor studies help prove?
Plate tectonics is real.
How did plate tectonics change geology?
It unified many geologic ideas.
Do all plates move the same way?
No, they move differently.
Why do continents move?
They are embedded in tectonic plates.
Why was Wegener’s hypothesis incomplete?
He thought only continents moved, not whole plates.