Weathering Flashcards
How are small rocks formed
Small rocks were broken down from larger pieces like boulders and mountains
What causes the earths surface to change?
Natural forces like the wind and rain
What are the 3 types of weathering?
- Physical
- Chemical
- Biological
What is physical weathering?
The mechanical or physical breakdown of rock into smaller pieces (sediments), without a change in the minerals chemical composition.
What is Exfoliation or onion skin weathering?
This is when the heat expands the out layer of the rock, and then at night the out layers contracts since it is cooler.
This mainly happens in the desert.
Over time this causes small pieces to flake off the rock
What is the onion skin weathering story?
- There was a rock
- The sun came up
- The rock got hot and got bigger
- Then it was night
- The rock got cold and smaller
- This happened everyday for a long time
- The rock began to crack and a layer of the rock falls off
What is freeze thaw weathering?
- When it rains water finds its way into a thin crack
- On cold nights the temperature falls and the water freezes.
- Ice expands by 9% and wedges the rock apart
- In the daytime the water thaws and sinks deeper into the crack
- After this has happened many times the crack widens until the rock is split in 2
- Small rocks then fall down the side of the valley and a called scree
https://www.youtube.com/watch?v=cwVF33jOmG8
What is abrasion?
When pieces of rock collide with each other due to transportation by wind. ice, water or gravity.
What is weathering?
The physical and chemical breakdown of rocks near the surface.
What is biological weathering?
Weathering caused by living things
What is responsible for most biological weathering?
Plants are responsible for most biological weathering
What are the 3 types of physical weathering?
- Abrasion
- Ice Wedging
- Onion Skin Weathering
How do plants cause biological weathering?
,1. Roots grow into weaknesses in the rock ansd as they grow cause these cracks to become larger
2. Lichens, algae, bacterial or mosses produce weak acids. They are all organisms which grows on rocks. It creates chemicals which erode at the rock as it grows
How do animals cause biological weathering?
Animals construct burrows to shelter in. This breaks apart or undermines rock leading to weathering
Other animals bore into rocks for protection either by scraping away grains or secreting acid to dissolve rock
What is chemical weathering?
The process by which chemicals breakdown rock through a change in the mineral composition,
This happens fastest in a hot, moist climate
What are the 3 types of chemical weathering?
- oxidation
- Dissolving
- hydrolysis
What is oxidation?
This occurs when oxygen from the air combines with iron rich minerals of the rock and this causes RUST
What is acidic rain?
Carbon dioxide from the atmosphere combines with the water to make the rain water slightly acidic
What is dissolving?
When the acidic rain falls on certain types of rock (limestone and marble) there is a chemical reaction which causes the rock to dissolve.
What is Hydrolysis?
Wter combines with minerals such as mica and feldspar found in granite, to form clay.
The rock weakens and crumbles apart