Geography revision guide By Billy Hewson

Contents page HAAC Processes HAAC Processes (Part 1) HAAC ProcessesHAAC Processes (Part 2) HAAC Processes HAAC Processes (Part 3) HAAC Processes HAAC Processes (Part 4)

HAAC Processes Hydraulic 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 Processes Abrasion Bits of rock and sand in waves grind down cliff surfaces like sandpaper.

HAAC Processes Attrition Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.

HAAC Processes Solution Acids contained in sea water will dissolve some types of rock such as chalk or limestone.

Costal Eroison

Sub aerial Processes Lists of subaerial Processes Freeze ThawRockfalls ExfoliationSoil creep Biological weatheringLandslides Chemical weatheringSlumping Mass movementMudflow

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.

Chemical weathering 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.