Weathering

Question 1

what is denudation?

Answer 1

Denudation is a long term process in which the wearing and tearing of the surface of the Earth takes place.

Question 2

What are the 2 main processes of denudation

Answer 2

Weathering and erosion.

Question 3

What is weathering?

Answer 3

Weathering is the process that physically changes solid rock into smaller pieces or sediments.

Question 4

What is erosion?

Answer 4

Erosion is the process that breaks down and moves the sediments away from their original positions. Erosion is caused by water, wind, moving ice (glaciers) and gravity.

Question 5

What is mechanical weathering?

Answer 5

Mechanical weathering is the physical breaking down of rocks into smaller pieces.

Question 6

Explain the most common type of mechanical weathering (3 steps). Detailed and simple version

Answer 6

Freeze-thaw action:

1. By day, water collects in cracks in the rocks.
2. At night, the water freezes and expands.
3. repeated freeze-thaw action causes the rock to shatter, and it falls to the bottom of the slope as scree.
4. Water gathers in the cracks of water during the day.
5. At night, the temp drops below 0 degrees celsius, the water freezes to become ice. This puts pressure on the rock as the ice expands. The next day the water thaws and melts again.
6. Repeated freezing and thawing results in the rock becoming weak and breaking into smaller pieces. These pieces then roll down the slope and gather, where they are known as scree.

Question 7

What is chemical weathering?

Answer 7

Chemical weathering is caused by chemical changes, when rock is dissolved or decays.

Question 8

Explain a type of chemical weathering (5)

Answer 8

Carbonation:

1. Rainwater dissolves carbon dioxide when falling
2. It mixes with the water to form a weak carbonic acid.
3. Limestone contains calcium carbonate. when the weak carbonic acid and rainwater mixture fall onto the limestone, a chemical reaction occurs.
4. The calcium carbonate begins to dissolve. This is known as carbonation.
5. Limestone is permeable. it has vertical cracks called joints and horizontal bedding planes.

Question 9

What are karst landscapes?

Answer 9

Karst landscapes are areas of land made up of limestone. the effects of carbonation are clearly seen here. e.g. the Burren in Clare.

Question 10

What are some surface features of karst landscapes?

Answer 10

The bare, rocky karst surface is called a limestone pavement. The pavement is made up of clints and grikes.

Question 11

What is a swallow hole?

Answer 11

When a river enters a karst landscape it can disappear underground through grikes which become swallow holes.

Question 12

What are the underground features of limestone caves?

Answer 12

Disappearing stream, swallow hole, limestone pavement, underground passage, cave, stalagmites, stalactites and pillars.

Question 13

Explain how stalactites and stalagmites are formed

Answer 13

Stalactites: When water containing carbonic acid drips from the roof of a cave, some of the droplets hang on the roof for a while and evaporates leaving behind a deposit of calcite. These stalactites build up over thousands of years.
Stalagmites: Water droplets drop onto the floor of the cave, they leave behind a deposit of calcite after evaporating. Over time these deposits build up on the floor and grow upwards to form stalagmites.

If a stalagmite and stalactite meet and join, they form what is called a pillar.

Question 14

What is biological weathering? (example as well)

Answer 14

Biological weathering takes place when rocks are worn away by animals, plants and living organisms. e.g. trees and plants can grow within the cracks in rocks. As the roots grow bigger they push open the cracks, making them wider and deeper. Over time the growing tree or plant eventually breaks the rock apart.

Question 15

What are grikes and clints?

Answer 15

Clints are the slabs of rock on the surface that separate the grikes.
Grikes are deep grooves in the pavement. They become weathered, widened and deepened by carbonation.