Weathering and Erosion Flashcards
What is weathering? Name its three types.
Weathering refers to the breaking down of rocks and boulders into pieces. It is of three types; physical weathering, chemical weathering and biological weathering.
What are natural causes of weathering?
Wind, water, rain, temperature, acid water and growing plants
What is physical weathering? Name it’s two types.
Physical weathering refers to the breaking down of larger rocks into small rocks by natural agents, such as temperature, ice, et cetera. There is no chemical change to the rock only physical disintegration. It is of two types, free-thaw weathering, and onion-skin peeling/exfoliation weathering
What is freeze-thaw weathering?
Main questions for this -
1. What are the conditions which need to be met for this type of weathering to occur?
2. What happens during this type of weathering?
Freeze-thaw weathering takes place, interpret regions with a higher altitude. At night, temperature is below freezing point and above freezing point in the day (10°C to 12°C to prevent evaporation). It occurs when the rocks are porous (contain holes) or permeable (allows water to pass through).
During freeze-thaw weathering, water seeps into a crack in the rock. At night, the temperature is drop below freezing point, causing the water to freeze and expand widening the crack. And the daytime the temperature rises above freezing point and hence the ice melts and water seeps further into the now widened crack. This process repeats continuously until the crack widens to a point where the rock splits in half.
What is onion-skin peeling/exfoliation weathering?
Main questions for this -
1. What are the conditions which need to be met for this type of weathering to occur?
2. What happens during this type of weathering?
Onion skin weathering takes place when the temperature range is high. For example in the daytime it is 50°C and at night, it is 20°C and hence the temperature range is 30°.
During onion skin weathering in the daytime, the rock surface hits up and expands. At night, due to the drop in temperature, the surf schools and contracts. This results in the outer layer, loosening up and the formation of track of cracks and joints in the outer layer of the rock. Ultimately, after this process of expansion and contraction repeats several times, the outermost layer peels off, looking like an onion skin, and the broken pieces fall to the ground.
What is chemical weathering? Name it’s three types.
Chemical weathering refers to the type of weathering where a chemical reaction occurs in the rock, causing it to dissolve/break down and form new substances caused by natural agents. It is of three types, carbonation, oxidation, and hydration.
What is carbonation?
Carbonation refers to the type of chemical weathering where CO2 and rainwater or moisture in the surrounding environment, chemically react to produce carbonic acid, a weak acid, that reacts with carbonate minerals in the rock. This simultaneously weakens the rock and removes chemically weather materials.
Formula -
CO2 + H2O -> H2CO3
CaCO3 + H2CO3 -> Ca(HCO3)2
What is oxidation?
Oxidation refers to the type of chemical weathering when O2 and H2O react with iron rich minerals in rocks and weakens the structure of the mineral. During oxidation, the minerals in the rock will change colour taking on a ‘rusty’, reddish-orange appearance.
What is hydration?
Hydration refers to the type of chemical weathering where the mineral structure in the rocks form a weak bond with H2O, causing the mineral grains to expand creating stress, which causes the disintegration of the rock. This often produces a new mineral compound that is larger than the original compound. This increased size expands rock and can lead to decay.
Hydration can also lead to colour changes in the weathered rock surface. For example, anhydrite can absorb two water molecules to become gypsum.
What is biological weathering? Give me 4 examples.
Biological weathering refers to the breaking down of rocks due to the actions of plants or animals. Some of these are chemical changes, whereas others are physical. There are various examples of biological weathering for such examples are plant roots, organism activity, lichen, algae, decaying plants and lastly, human activity.
How do plant roots cause weathering?
The most common form of biological weathering is when plants roots penetrate into cracks and crevices of rocks and cause the rock to split or break into smaller pieces through mechanical weathering. This is because the roots cause pressure to the pressure to the rock walls, causing the cracks to widen.
How does organism activity cause weathering?
Some animals may borrow or tunnel into rocks or cracks in the rocks and cause the rock to break down and disintegrate. Small animals, worms, and other insects often contribute this form of biological weathering. Small organisms such as snails, barnacles, or limpets, attach themselves to rocks and secrete acids. These acids chemically dissolve the Earth’s surface.
How do lichen, algae and decaying plants cause weathering?
The biochemical weathering process, leeches minerals from the rock, causing it to weaken and breakdown.
The decaying of plant materials can also produce acidic compounds which dissolve the exposed rock.
The presence of organisms growing expanding or making across the surface of the rock also exerts a certain amount of pressure that gradually cause both mechanical and chemical weathering of the rock as organisms extract various minerals.
How do human activities cause weathering?
Walking, quarrying, mining, and construction are examples of human activities which result in the weathering of rocks. Human activities, such as the construction of roads and railways in mountains, building road networks, industries, et cetera, break mountains and rocks down into smaller particles.
What is erosion?
Erosion refers to the process by which the broken materials from weathering are carried away from their original place to a different place
What are natural causes of erosion?
The natural causes of erosion are glaciers, wind, rivers, and the ocean.
(Wind, water, and ice)
What is an equilibrium?
An equilibrium refers to the balancing nature of natural elements
What is the purpose of weathering and erosion?
The purpose/results of weathering and erosion are:
1. Land building
2. Fertile Soil
3. Recycling of Earth’s materials
