Factors affecting weathering



Can you explain why these rocks look the way they do?

Limestone Scenery - down in a gryke, Desert de Plate, Flaine, France



Mineral composition

mineral is a naturally occurring, inorganic, crystalline solid, that has a definite chemical composition, and is stable over a range of temperatures and pressures.

Example - Quartz is a mineral, it is found in nature, it forms without the help of plants and animals, it is crystalline, and it has a definite chemical composition (SiO2, two oxygen atoms for every one silicon atom). It is stable, both at low and high temperatures, but is unstable at very high temperatures ( > 600 C).

A rock is a combination of one or more minerals. It may be igneous, sedimentary or metamorphic.

Example - A mixture of crystals of quartz and feldspar is a rock called granite. Granite may also have other minerals such as micas, pyroxene, and amphiboles in lesser amounts, as well as many others in trace quantities.

Although there are over 4000 different minerals and hundreds of rock types, there are only about 8 common minerals and 20 common rocks found at the Earth's surface.

In terms of minerals, quartz is resistant to weathering and calcite is very susceptible to weathering.

In terms of rocks quartzite and sandstone are resistant to weathering. Granite is less resistant to weathering than quartzite and sandstone. Limestone and marble are very susceptible to weathering.

  1. What is quartzite?
  2. What is limestone?
  3. Why is quartzite more resistant to weathering than limestone?

Grain (Particle) size

Grain (particle) size
  1. Explain how grain size can affect the rate of weathering of a rock or soil.

Presence of lines of weakness

Extreme Environments - A ski station, in a limestone landscape, in the summer - summit of les Grandes Platières, Flaine, France
  1. Explain how the presence of grikes and clints on limestone pavement demonstrates the effect of lines of weakness on the rate of erosion of limestone.


Speed of a chemical reaction increases 2 and a half times with each rise in temperature of 10 degrees Celsius.

  1. Describe the conditions of temperature and rainfall where strong chemical weathering takes place.
  2. Describe the conditions of temperature and rainfall where strong physical weathering takes place.
  1. Use the two graphs above. What kind of weathering is dominant in the Tropical Rainforest?
  2. What kind of weathering is dominant in the Tundra?
  3. What kind of weathering is dominant in the Temperate Forest?