Geography Topic 4 - Coasts

Coast

The part of the land adjoining or near the sea.

Weathering

The breakdown or deterioration of rocks.

Erosion

The wearing away of rocks and Earth's surface.

Biological Weathering

Type of weathering. Occurs when plants on the coastline grow roots into the rock, breaking it away

Chemical Weathering

Type of weathering. Occurs when rain or sea water, (which is slightly acidic) causes rocks to decompose

Physical Weathering

Type of weathering. Occurs when water gets into cracks in the rock. It evaporates and leaves salt behind. The crystals grow over time, causing the rock to break apart.

Swash

When a wave breaks and travels up the beach.

Backwash

When a wave travels back to the sea due to gravity.

Fetch

The distance of water over which a wave travels.

Regolith

Soft rock material that decomposes during chemical weathering.

Name the two types of waves

-Constructive

-Destructive

Name 6 characteristics of constructive waves

• low and wide

• strong swash, weak backwash

• flat

• build structures

• <8 per minute

• elliptical movement

Name 6 characteristics of destructive waves

• high

• weak swash, strong backwash

• not flat

• erodes beaches

• >15 per minute

• circular movement

Abrasion

Caused by large waves hurling things against a cliff.

Attrition

Caused by waves forcing rocks against each other.

Solution

Caused by salts and acids dissolving cliffs.

Hydraulic Action

Caused by waves compressing air in cracks, breaking rocks apart.

How are headlands and bays formed?

• Hard rock and soft rock make up a cliff face

• Soft rock gets eroded, but hard rock doesn’t

• This leaves pockets of sea in the cliff called bays, whereas the sticky-out bits of rock are called headlands.

How are caves, arches, stacks and stumps formed?

• A fault opens in the rock

• Due to hydraulic action, the fault enlarges and forms a notch

• Abrasion and hydraulic action widen the notch into a cave

• Due to erosion, the cave opens and forms an arch

• The arch widens and the roof can’t support itself so it collapses.

• This leads to a stack, which is standing, but being undercut.

• The stack collapses, leaving a stump.

How are wave-cut platforms formed?

• Waves erode bits of rock at the bottom of a cliff

• This leaves a ledge, which collapses under its own weight, forming a wave-cut platform

Longshore Drift

• Transportation of material along the coast by waves.

• Waves hit the beach at an angle

• Swash carries the sediment up the beach at an angle

• Backwash carries sediment down the beach (perpendicularly)

• Constructive waves transport material to the beach

• Destructive waves transport material away from the beach

How are spits formed?

• A coastline will sometimes change direction, but the direction of the prevailing wind won’t always follow it.

• When enough material is deposited, due to longshore drift, little islands (spits) are formed, which are separate from the mainland

How are bars formed?

Formed when a spit grows across a bay and joins two headlands.

How are tombolos formed?

Formed when a spit connects the mainland coast to an island.

Mountainous coastline

A coastline dominated by mountains.

Headlands and bays coastline

A coastline dominated by headlands and bays

Coastal plain coastline

A flat area by the sea

Delta coastline

A coastline near a delta, where the river meets the sea.

Reef coastline

A coastline dominated by coral

Glaciated coastline

A coastline dominated by ice.