Rivers and coasts Flashcards
what are destructive waves?
> Has a stronger backwash than swash
>7-10 waves per minute
what are constructive waves?
> has a stronger swash than backwash
>10-15 waves per minute
what is a solution?
minerals dissolved in water and carried along in the solution
what is traction?
when large rocks or boulders roll along the river bed
what is saltation?
small pebbles and stones are bounced along the river bed.
what is suspension?
fine light material is carried along in the water.
What is hard engineering?
->An immediate, long lasting but expensive coastal defence
E.g. Rock armour, gabions, groynes, sea walls
Works against natural processes by man made fences against coastal erosion
how are wave-cut platforms formed?
- Erosion (mostly destructive waves) cause a wave cut notch.
- causes rock above to collapse (less stable)
- waves wash away the collapsed cliff debris and erode cliff again
- stages 1-3 repeat and a wave-cut platform is made
How does free-thaw weathering work?
- water enters crack in a rock
- water freezes and expands
- ice melts and water goes deeper into the rock
- process repeats until rock breaks
How does biological weathering work?
- plant roots can get into small cracks in a rock
- As roots grow the crack enlarges
- causes small pieces or rock to break away
What is chemical weathering?
Rain and seawater can be a weak acid and dissolve rock like limestone and chalk.
What is mass movement?
Downhill movement of sediment caused by gravity?
What are the types of mass movement?
R
What is attrition?
Pieces of bed load hit each other causing them to break and become smaller and rounded
What is abrasion?
Rocks being picked up and thrown against a beach, bed or cliff
