From sand to new rock
Slow water drops its load. Time makes rock.
Where does the load go?
A river carries sand, soil and small stones. At last the river reaches a lake or the ocean, and the water slows down.
What do you think happens to the load the water carries?
What this lesson covers
The idea
When the speed of water or wind decreases, the eroded material settles at the bottom, and these sediments harden over time into new rocks, a change taking thousands of years that cannot be reversed.
Where does the load go?
A river carries sand, soil and small stones. At last the river reaches a lake or the ocean, and the water slows down.
What do you think happens to the load the water carries?
- It settles at the bottom
- It floats on top forever
- It turns into water
Slow the water
Slide the speed down. When everything has settled, press Wait a very long time.
Settled, then hardened
Fast water carried the sediments. Slow water could not, so they settled at the bottom. After a very long time the layers hardened into rock.
When the speed of water or wind decreases, the eroded material settles at the bottom, and these sediments harden over time into new rocks. This takes thousands of years and cannot be reversed.
Notes
When the speed of water or wind decreases, the eroded material settles at the bottom. These sediments harden over time into new rocks, a change taking thousands of years that cannot be reversed.
Check yourself
When does eroded material settle at the bottom?
Where does this settling often happen?
How do the settled sediments become new rocks?
Can hardened sediments easily turn back into loose sand and soil?
- When the speed of the water or wind decreases — correct. Yes!
- When the water moves faster. Fast water carries the material along.
- Only when it is very hot. Heat is not what makes it settle. Slower water does.
- On the top of a mountain peak. Settling happens where water slows down, such as a lake or an ocean.
- In a fast waterfall. A waterfall moves fast and keeps carrying things.
- In a lake or an ocean — correct. Yes!
- They melt in one day. Nothing melts. Hardening takes thousands of years.
- Someone cuts them out. Sediments harden into rock slowly by themselves.
- They harden over a very long time — correct. Yes!
- No, the change cannot be reversed — correct. Yes!
- Yes, in one day. This change takes thousands of years and cannot be reversed.
- Yes, if we stir them. Stirring does not undo it. The change cannot be reversed.