Coasts Flashcards
Wavelength
The distance between two successive crests or troughs
Wave height
The distance between the trough and the crest
Wave frequency
The number of waves per minute
Velocity
The speed of a travelling wave - influence by wind, fetch and water depth
Fetch
The amount of open water over which a wave has passed
Swash
The movement of water up the beach
Backwash
The movement of water down the beach
What are the two different types of waves?
Constructive and destructive waves
What characterises constructive waves?
Sediment is transported landwards
What characterises destructive waves?
Sediment is dragged seawards
Longshore drift
Waves move up the beach in one direction, but the waves draining back down the beach take a different route; this action tends to transport materials along the beach
TYPES OF EROSION: Hydraulic action
Occurs as waves hit or break against a cliff face
TYPES OF EROSION: Abrasion
The process of breaking wave hurling materials, such as pebbles or shingle, against a cliff face
TYPES OF EROSION: Attrition
The process in which eroded material, such as broken rock, is worn down to form smaller, rounder beach material.
TYPES OF EROSION: Solution
Occurs on limestone and chalk. Calcium carbonate, a salt found in these rocks, dissolves slowly in acidic water.
What are a few features of erosion?
- cliffs
- caves
- arches
- stacks
- stumps
- wave cut platform
Beach (the technical term ;-)
The term beach refers to the accumulation of material deposited between low spring tides and the highest point reached by storm waves at high spring tides.
HWM
High water mark - the level reached by the sea at high tide.
LWM
Low water mark - the level reached by the sea at low tide
What are the three zones of a ‘typical beach’?
- backshore
- foreshore
- offshore
Backshore
Marked by a line of dunes or a cliff
Foreshore
Exposed at low tide
Offshore
Waves touch the sea bed, material is usually disturbed and sometimes pushed up as offshore bars
Spit
A beach of sand or shingle linked at one end to land.
Tombolos
Ridges that link the mainland to an island
Succession
The growth of new plants
What are coral reefs?
Coral reefs are calcium carbonate structures, made up of reef-building stony corals
Fringing reefs
These are the reefs that fringe the coast of a landmass
Barrier reefs
Example: the Great Barrier Reef
Occur at a greater distance from shore than fringing reefs and are typically separated from it by a deep, wide lagoon
Atoll reefs
Rise from submerged volcanic foundations
Mangroves
Mangroves are salt-tolerant forests of trees and shrubs that grow in the tidal estuaries and coastal zones of tropical areas
What has been named one of the most dangerous natural hazards to people and the environment?
Hurricanes (in Asia, also known as tropical cyclones)
What do hurricanes do?
Move excess heat from low latitudes to higher latitudes
FUN FACT ABOUT HURRICANES
The path of a hurricane is erratic, so it is not always possible to give more than 12 hours notice.
What is the lowest windspeed of a hurricane?
A storm is not classed as a hurricane unless it has a wind speed of over 118 km/hr
