Sea Level Lecture 4- Where the land and the oceans meet: Sea level and coastal processes Flashcards
Name three features of high energy coastlines.
Waves
Beaches and Dunes
Barriers
Name three features of low energy coastlines.
Estuaries
Intertidal zones
Wetlands
Are high energy coastlines long term depositional environments?
No
Can dune like systems develop on high energy coastlines?
Yes
What is fetch?
Area over which waves are travelling and direction wind is blowing
What controls global wave power?
Wind
Distance
Fetch
What are ‘roaring fourties’?
Southern Hemisphere wave power uninterrupted fetch.
What latitudes have strong global wave power?
Mid latitudes
What happens in deep water? (linear wave theory)
- particles flow in circular motion
- Orbit radius decreases with depth
What happens in intermediate water? (linear wave theory)
Elliptical near sea bed, then to and fro
Disturb sediment at sea floor
What happens in shallow water? (linear wave theory)
Horizontal, to and fro, uniform with depth
Able to move material
Do waves move through the water or does water move?
Waves move through the water
When does shoaling start?
As waves move in when depth is half the wave length.
Why do waves start to steepen and get closer together near the shore?
Friction
What is shoaling?
Wave shoaling is the change in shape and behaviour as waves propagate into water of decreasing depth.
What are the 5 nearshore zone regions?
Deep water
Shoaling zone
Breaker zone
Surf zone
Swash zone
When are rates of transport greatest?
When wave approach is around 45 degrees
Where does longshore current occur?
Anywhere where waves are refracted as they approach the shoreline (i.e. are at an oblique angle).
What happens at gravel beaches?
Transport occurs primarily in the swash zone (uprush of wave onto the beach)
What happens at sandy beaches?
Transport generally occurs in the entire surf zone
What are beaches?
Accumulations of sand or gravel along shorelines deposited by waves and wave induced flows.
Globally what % of coastlines are sandy beaches?
20%
Globally what % of coastlines are gravel beaches?
10%
What identifies a beach?
From low tide mark to next geomorphic feature such as a dune or sea wall.