Geomorphic Processes

Question 1

Freeze-thaw

Answer 1

Water gets into cracks in the rocks from rainfall or melting snow or ice, and when temperatures reach below zero degrees, the water begins to freeze and expand. When the temperature increases again, the ice melts, and when this process repeats itself it can cause the rock to shatter

Question 2

Pressure release

Answer 2

Overlying materials are removed by erosion (or other processes) which causes underlying rocks to expand and fracture parallel to the surface. The underlying rock is under a large amount of pressure from the overlying rock, and when the rock is exposed, the pressure on them is released, the outside of the rock expands and causes stress which results in fractures

Question 3

Thermal expansion

Answer 3

Expansion and contraction of rock occurs due to changes in temperature. If the temperature of the rock differs in the outer and inner layers then it can exfoliate

Question 4

Salt crystallisation

Answer 4

Salt water enters small cracks in the rock and then evaporates, leaving salt crystals behind. When the salt crystals accumulate, pressure is applied to the crack, causing it to expand and eventually break up

Question 5

Traction

Answer 5

Sediment rolls along, pushed by waves and currents (pebbles, boulders cobbles)

Question 6

Saltation

Answer 6

Sediment bounces along, either due to the force of water or wind (sand sized particles)

Question 7

Hydration

Answer 7

Water molecules added to rock minerals create new minerals of a larger volume (e.g. when anhydrite takes up water to form gypsum). Hydration causes surface flaking in many rocks. Some minerals also expand about 0.5% during the chemical change because they absorb water.

Question 8

Solution

Answer 8

Dissolved material is carried in the water as a solution

Question 9

Rockfall

Answer 9

Rock fragments fall from the cliff face due to gravity. This rock is loosened due to freeze-thaw weathering, when water enters the cracks in the rock and then freezes, expanding and therefore loosening the rock

Question 10

Organic acids

Answer 10

Produced during decomposition of plant and animal litter cause soil water to become more acidic and react with some minerals in a process called chelation. Blue-green algae can have a weathering effect, producing a shiny film of iron & manganese oxides on rocks. On shore platforms molluscs may secrete acid which produce small surface hollows in the rock

Question 11

Abrasion

Answer 11

Waves containing rock particles scour the coastline (rock rubbing against rock)

Question 12

Attrition

Answer 12

Rock collide with each other and become worn away. They become smaller, smoother and more rounded, eventually producing sound

Question 13

Corrosion

Answer 13

Dissolving minerals in coastal rock. Not normally affected by seawater unless it is polluted or acidic. Only coastal rocks with lots of dissolvable minerals such as magnesium carbonate should be affected

Question 14

Landslide

Answer 14

Rocks that are jointed or have bedding planes roughly parallel to the slope or cliff surface, are susceptible to landslides. An increase in the amount of water can reduce friction- causing sliding. In a rock landslide, slabs of rock/blocks can slide over underlying rocks along a slide or slip plane

Question 15

Quarrying/Pounding

Answer 15

The ‘sledge hammer’ effect of tonnes of water crashing against cliffs. It shakes and weakens the rocks leaving them open to attack from hydraulic action and abrasion.

Question 16

Carbonation

Answer 16

The mixing of water with carbon dioxide to make carbonic acid. This type of weathering is important in the formation of caves. Dissolved carbon dioxide in rainwater or in moist air forms carbonic acid, and this acid reacts with minerals in rocks

Question 17

Solution (weathering)

Answer 17

As rain falls, it dissolves small amounts of carbon dioxide from the air, forming a weak acid that is able to dissolve limestone. It dissolves even more carbon dioxide as it seeps through the soil

Question 18

Hydrolysis

Answer 18

The chemical breakdown of a substance when combined with water. The most common example of hydrolysis is feldspar in granite rocks changing to clay

Question 19

Plant roots (weathering)

Answer 19

Plant roots grow down into cracks in the rock, causing them to weaken, and eventually collapse

Question 20

Rock boring

Answer 20

When animals bore into the rock, causing it to weaken