Geography revision guide

By Billy Hewson

Contents page

HAAC Processes (Part 1)

HAAC Processes (Part 2)

HAAC Processes (Part 3)

HAAC Processes (Part 4)

HAAC ProcessesHydraulic action

Air may become trapped in joints and cracks on a cliff face. When a wave

breaks, the trapped air is compressed which weakens the cliff and causes

erosion.

HAAC ProcessesAbrasion

Bits of rock and sand in waves grind down cliff surfaces like sandpaper.

HAAC ProcessesAttrition

Waves smash rocks and pebbles on the shore into each other, and they

break and become smoother.

HAAC ProcessesSolution

Acids contained in sea water will dissolve some types of rock such as

chalk or limestone.

Costal Eroison

Sub aerial Processes Lists of sub aerial Processes

Freeze Thaw Rockfalls

Exfoliation Soil creep

Biological weathering Landslides

Chemical weathering Slumping

Mass movement Mudflow

Mass movement

Mass movements occur mostly on steep slopes of land and there are many different processes of them.

Freeze Thaw

Most rocks are very hard. However, a very small amount of water can cause them to break. When water seeps into

cracks and freezes it then expands. This powerful force can increase the

size of cracks. Over time the repeated freeze-thaw action of water can break rocks apart. Eventually, pieces of rock

break off creating scree.

Rockfalls

Rockfall is the rapid, free fall of rock from a steep cliff face. Rock fragments fall from the face of the cliff because of

the action of gravity.

Exfoliation

Exfoliation,  separation of successive thin shells, or spalls, from

massive rock such as granite or basalt; it is common in regions that have

moderate rainfall. The thickness of individual sheet or plate may be from a

few millimetres to a few metres.

Soil creep

Soil creep is a very slow movement, occurring on very gentle slopes because

of the way soil particles repeatedly expand and contract in wet and dry

periods. When wet, soil particles increase in size and weight, and expand at right angles. When the soil dries out, it contracts vertically. As a result, the

soil slowly moves downslope.

Biological weathering

Animals and plants can wear away rocks. This is

called biological weathering. For example, burrowing animals such as rabbits can burrow into a crack in a

rock, making it bigger and splitting the rock.

Landslides

Landslides are occasionally a rapid movement of earth or rock sliding

along a concave plane. They can occur after of heavy rain, when the water saturates overlying rock making it

heavy and more likely to slide. Undercutting of a steep slope by river

or sea erosion weakens the rock above, also making a slump to appear.

Chemicalweathering

The weathering of rocks by chemicals is called chemical weathering.

Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it. Minerals in rocks may react with the rainwater, causing the

rock to be weathered.

Slumping

Slumping involves a whole segment of the cliff moving down flat slope to a

Mudflow

Mudflow occurs on steep slopes at about 10 to 20 degrees. It's a sudden movement which occurs after many months of heavy rain. When there is not enough ground to hold the soil in place, saturated soil flows over other layers of soil, causing dangers and

other natural hazards.