C4.2 Sedimentary rocks Flashcards
What are sedimentary rocks?
Sedimentary rocks are rocks made from sediments.
Give some properties of sedimentary rocks.
Sedimentary rocks:
- are soft and easily scratched
- contains layers
- made up of separate grains
- porous
- reacts with acid
- formed when sediments settle on top of each other.
- some contains fossils
Give some examples of sedimentary rocks.
E.g Sandstone, limestone and chalk are sedimentary rocks.
What is weathering?
Weathering breaks down all types of rock into smaller pieces, called sediments.
Weathering makes sediments but it doesn’t move them away from the original rock.
Give the names of types of weathering.
Different types of weathering include freeze thaw weathering, biological weathering and chemical weathering.
What are sediments?
Sediments are pieces of rock that have been broken away from their original rock.
What is physical weathering?
Physical weathering is the breaking up or wearing down of rocks by the effects of changing temperature.
What is biological weathering?
Biological weathering is the breaking up or wearing down of rocks by the action of living things.
What is chemical weathering?
Chemical weathering is the breaking up or wearing down of rocks by the action of chemicals such as those in rainwater. Acids in the rain, such as sulphuric acid or carbonic acid, react with minerals in the rock, weakening them in some way.
What is freeze thaw weathering?
In freeze thaw weathering, water gets into small cracks in the rock. When the temperature is cold, the water freezes. The water expands as it freezes. This creates forces against the side of the rock causing cracks in the rock. The water melts and freezes again, and eventually, a fragment of the rock breaks away completely.
What is erosion?
The process of the breaking down of the rocks and the movements of the rocks away from their original rock is called erosion.
What is transport?
Transport processes move sediments away from their original rock. Water, ice, wind and gravity can all move sediments.
What is compaction and cementation?
Over many years, deposited sediments may join together to make new rocks. This could happen by:
-Cementation : Another substance joins the sediments together
or
-Compaction : The weight of the sediments above squashes the sediments below
What is deposition?
Eventually, when sediments stop moving, they settle in one place. This is called deposition. Layers of different types of sediment may settle on top of each other.
Define porous.
A porous material has small gaps that may contain substances in their
liquid or gas states. Water can soak into a porous material.
