Unit 11: Earth's Land — Rocks and Change
What's beneath your feet, how mountains get built and worn back down, and the slow-motion collisions that shake and reshape the ground.
9 topics · 31 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
- How it worksHow does Earth sort itself into a thin crust, a thick mantle, and a metal core, from the surface to the center?
- Worked exampleFind how much thicker Earth's mantle is than its crust if the mantle is about 2900 kilometers thick and the crust is about 30 kilometers thick.
- Common mistakeWhy isn't the mantle a layer of liquid lava sitting right underneath the crust?
Your turn1 of 2
Find how much thicker Earth's mantle is than its crust if the mantle is about 3045 kilometers thick and the crust is about 34 kilometers thick.Rocks and the Rock Cycle
- How it worksHow do heat and pressure turn one type of rock into another as it cycles between igneous, sedimentary, and metamorphic?
- How it worksWalk me through how melted magma cools into igneous rock, gets worn down into sediment, and gets pressed into sedimentary rock.
- Common mistakeWhy doesn't the rock cycle have one fixed starting point or ending point?
- Going furtherWhat happens to a sedimentary rock that gets pushed deep underground and squeezed under enormous pressure?
Your turn1 of 2
The rock cycle transforms rocks between igneous, sedimentary, and metamorphic types using heat, pressure, and weathering. Does the rock cycle have one single fixed starting point where it always begins?Minerals
- How it worksHow does a mineral's hardness, color, and how it breaks help identify exactly which one it is?
- Common mistakeWhy isn't a rock the same thing as a mineral, even though rocks are made of minerals?
- Going furtherWhat happens to a mineral's crystal shape when it forms slowly underground compared to cooling quickly at the surface?
Your turn1 of 2
Mineral A has a hardness of 7 and mineral B has a hardness of 6 on the Mohs scale. Find the harder of the two hardness numbers.Soil
- How it worksHow do broken-down rock, decayed plants and animals, water, and air combine to make soil?
- Common mistakeWhy isn't soil just crushed-up rock with nothing living or once-living mixed into it?
- Going furtherWhat happens to a farm's soil quality after the same crop is grown in it year after year with nothing given back?
Your turn1 of 2
Why does it take hundreds of years to form just one inch of soil?Weathering
- How it worksHow does water freezing and expanding inside a rock's cracks break the rock apart bit by bit?
- Common mistakeWhy isn't weathering the same process as erosion, even though both wear rock down?
- Going furtherWhat happens to how fast a rock weathers in a rainy climate compared to a dry desert?
Your turn1 of 2
Why do sharp mountain peaks slowly turn into smooth, rounded hills over millions of years?Erosion and Deposition
- How it worksHow does moving water, wind, or ice pick up loose rock in erosion and drop it back down in deposition?
- Worked exampleFind how a river's speed slowing from 2 meters per second to 0.5 meters per second changes what size rocks it can still carry.
- Common mistakeWhy doesn't erosion move soil along one straight, simple path from start to finish?
- Going furtherWhat happens to a river's canyon over millions of years of the same water cutting through the same rock?
Your turn1 of 2
Find how many times slower a river's speed becomes if it slows from 3 meters per second to 0.619 meters per second.Volcanoes
- How it worksHow does melted rock rising from deep underground build pressure until it forces its way out at the surface?
- Common mistakeWhy doesn't every volcano look like the tall, cone-shaped mountain most people picture?
- Going furtherWhat happens to the type of eruption when magma is thick and full of trapped gas versus thin and runny?
Your turn1 of 2
Why does one volcano erupt in a slow, flowing river of lava while another explodes violently into ash?Earthquakes
- How it worksHow does stress building up along a crack in Earth's crust release suddenly as an earthquake?
- Worked exampleFind how many times stronger the shaking is between a magnitude 5 and a magnitude 7 earthquake, if each whole number is about 10 times stronger.
- Common mistakeWhy doesn't earthquake weather actually exist as a way to predict when one will strike?
Your turn1 of 2
Find how many times stronger the shaking is between a magnitude 4 and a magnitude 7 earthquake, if each whole number is about 10 times stronger.Plate Tectonics
- How it worksHow do giant plates of Earth's crust slowly drift on top of the flowing mantle underneath them?
- How it worksWalk me through what happens where two plates collide, pull apart, or slide past each other.
- Worked exampleFind how far two plates drift apart over 100 years if they move 5 centimeters every year.
- Common mistakeWhy don't plates move too slowly for anyone to have ever actually measured their motion?
- Ties togetherHow does plate tectonics explain why volcanoes and earthquakes cluster along the same lines on a map?
Your turn1 of 2
Find how far two plates drift apart over 351 years if they move 7 centimeters every year.