1. 8.4 Sedimentary rocks
Weathering breaks up rocks into smaller pieces, or sediments. There are 3 types of weathering…

2. 8.4 Sedimentary rocks
Chemical weathering…
…happens when acids in rainwater react with some rock minerals. Chemical weathering makes gravestone writing go blurry.

3. 8.4 Sedimentary rocks
Biological weathering…
… happens when plant roots or animal actions break up rocks.

4. 8.4 Sedimentary rocks
Physical weathering…
for example freeze-thaw weathering, happens when water gets into rock cracks:
On cold nights, water freezes.
When water freezes, it expands.
The ice pushes against the sides of the crack. The crack gets bigger.
This happens again and again. The rock breaks.

5. 8.4 Sedimentary rocks
Erosion
Sediments are transported away by water, wind, gravity or ice. This is erosion.

6. 8.4 Sedimentary rocks
When rivers reach the sea, they slow down. The tiny sediments suspended in the water drop to the bottom and settle in a layer. This is deposition, or sedimentation.
New layers settle on top of older layers.
Eventually the sediments in the layers stick together. This is cementation.
The layers become hard. They are now strata.