Unit 1: Earth's Structure and Interior
What Earth is actually made of on the inside, and the geophysical clues that revealed it, since nobody has ever drilled anywhere close.
4 topics · 14 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Earth's Layers by Composition
- How it worksHow did heavier iron sink to Earth's center while lighter rock floated up to the surface?
- How it worksWalk me through the crust, mantle, and core from the surface down to the center.
- Worked exampleFind how thick the mantle is if Earth's radius is 6371 km, the crust is 35 km, and the core's radius is 3486 km.
- Common mistakeWhy isn't the mantle a layer of liquid magma sitting right under the crust?
Your turn1 of 2
Earth's radius is 6370 km, the crust is 39 km thick, and the core's radius is 3493 km. How thick is the mantle?Earth's Layers by Physical Behavior
- How it worksHow does the rigid lithosphere sit on top of the slowly flowing asthenosphere underneath it?
- How it worksWalk me through why the outer core is liquid but the even hotter inner core is solid.
- Common mistakeWhy isn't the lithosphere the exact same layer as the crust?
- Going furtherWhat would change about plate tectonics if the asthenosphere were rigid instead of slowly flowing?
Your turn1 of 2
The lithosphere, crust plus the rigid uppermost mantle, is about 126 km thick, while the crust alone beneath it is only 28 km thick. How many kilometers of rigid uppermost mantle does the lithosphere include beneath the crust?How Earth Differentiated Into Layers
- How it worksHow did heat from asteroid impacts and radioactive decay melt the young Earth enough to separate?
- How it worksWalk me through iron sinking through molten rock to form Earth's core in the first place.
- Ties togetherHow does Earth's layered interior connect to the rigid plates riding on top of it today?
Your turn1 of 2
The young Earth accumulated from countless smaller rocky bodies colliding together, cold and solid at first. Why did the young Earth need to melt almost completely before it could sort itself into layers?Earth's Magnetic Field and the Dynamo
- How it worksHow does swirling liquid iron in the outer core generate Earth's entire magnetic field?
- Common mistakeWhy doesn't Earth's magnetic field come from a giant permanent bar magnet at its center?
- Going furtherWhat happens to compass readings around the world during one of Earth's magnetic pole reversals?
Your turn1 of 2
Earth's magnetic poles reverse irregularly, with individual gaps between reversals varying widely around a rough average of 200 thousand years. The current normal polarity has lasted about 809 thousand years so far. Approximately how many times longer than that 200 thousand year average is the current interval?