A-Level地理-冰层运动Action of Ice。

2016-08-26 13:36

来源：新东方整理

作者：上海新东方

Revision: Action of Ice

Definitions

Factors Determining the Nature of Coasts

Formation of Waves

Wind blows over the sea surface.
The surface of the sea exerts frictional drag on the lower layer of the wind.
The top layer (with the least drag) moves faster than the lower layer and hence tumbles over it.
This causes a circular motion of wind energy that acts on the sea to create waves.

Wave Erosion
Wave erosion like river erosion involves 4 processes:

Abrasion/Corrosion: The wearing away of the sides and the bed of a river by the impact of the load.
Hydraulic Action: Erosion by the force of moving water.
Attrition: The breaking down of the load by particles hitting against each other.
Solution/Corrosion: When minerals dissolve in water.

Features Produced by Wave Erosion

A notch is cut by waves at high tide level and developed further.
As this notch is developed, a cliff is formed.
The cliff steepens as weathering attacks the base further.
As the cliff retreats, the rock debris is swept by the backwash creating a wave-cut platform.
Some of the debris collects along the seaward edge of the wave-cut platform forming and off-shore terrace.

Caves, Geos, Arches and Stacks

An arch is created when a cave in a headland is eroded right through i.e. the inlet has two openings

When the arch collapses, the end of a headland stands up as a stack.

Headlands and Bays

These are formed in areas of alternating resistant and less resistant rocks.
Erosion/wave action acts less on the more resistant rock creating headlands and more on the less resistant rock creating bays.

Factors Affecting the Rate of Wave Erosion

Wave Transport
Sources of the load include:

Process: Swash (forward moving waves) and backwash push and drag material up and down the shore resulting in longshore drift.

Wave Depositional Features

Beach: Formed by deposition of mud, sand or pebbles along the coast.
Barrier Beach: A long ridge of sand parallel to but separated from the coast ridge by a lagoon.
Spit: A narrow ridge of sand joined to the mainland with the other end terminating in the sea
Bar: A ridge of material (usually sand) lying parallel to the coast
Tombolo: A ridge joining an island to the mainland
Offshore Bar: Developed on the gently sloping seabed. Occurs when sand is thrown up by waves breaking close to the coast.
Mudflat: Developed when tides/waves deposit fine sand along gently sloping coasts particularly in bars and estuaries.

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