Chapter 6: Weathering And Mass Movement

Question 1

Denudation

Answer 1

Rocks and soil of the Earths crust being worn down.

Question 2

Two main processes of denudation

Answer 2

Weathering

Erosion

Question 3

Weathering

Answer 3

Weathering is the breaking down of rocks and soil that are exposed to the weather. Two types of weathering: Mechanical weathering and Chemical weathering.

Question 4

Erosion

Answer 4

The breaking down of rocks and soil and the transportation of the eroded material.
Its caused by:
Moving water
Moving ice
Moving air

Question 5

Mechanical weathering

Answer 5

Mechanical weathering breakd up rocks into smaller pieces by putting pressure on the rock. Freeze-that action is an example of this.

Question 6

Freeze Thaw action

Answer 6

1. During the day, water seeps into cracks in the rock
2. At night, temperatures fall below freezing point. The water in the cracks freezes and expands, putting pressure on the rock
3. This process is repeated, windening the crack and joints in the rock, causing it to weaken, and eventually pieces break off. The broken-down rock is known as scree.
   Example: Croaigh Patrick in Co. Mayo

Question 7

Chemical weathering

Answer 7

Chemical weathering is when rocks are dissolved because of a chemical reaction. Carnonation is an exmple of this.

Question 8

Carbonation

Answer 8

The atmosphere contains a gas called carbon dioxide. (Co2)
Rainwater mixes with the Co2 to form a weak carnonic acid.
This weak carbonic acid has a huge effect on limestone rock. This is because limestone contains 80% calcium carbonate.
The weak carbonic acid reacts with the calcium carbonated in the limestone and dissolves it.
Limestone is a permeable rock, so rainwater can pass right down the rock.

Question 9

Karst landscapes

Answer 9

An area where bare limestone is exposed to the weather

Question 10

Landscape pavement: Limestone pavement

Answer 10

Rainwater fall onto the exposed limestone and passes through vertical koints or cracks in the limestone.
Carbonation makes the joints wider by dissolving the calcium carbonate in the limestone until they then look like grooves or gaps in the limestone. These are called grikes. The blocks left in between the grikes are called clints.

Question 11

Swallow hole

Answer 11

Rivers that flow over a limestone surface can disappear underground through a swallow hole.

Question 12

How a swallow hole is formed

Answer 12

As the river flows over limestone, the water widens the joints in the rocks through carbonation.
Eventually the river disappears from the surface and begins to flow underground along the bedding planes.
Carbonation and the physcal force of the moving water, called hydraulic action, enlarge the joints and bedding planes.
The place where the river disappears underground is called a swallow hole.
The river continues to flow underground, forming underground karst features such as passages and caves.

Question 13

Caves and caverns: Stalactites

Answer 13

As the water seeps through the rock, it carries dissolved limestone with it. Some of this water eventually reaches the roof of a cave or a cavern below ground.
The drops slowly evaporate and leave behind small deposits of pure limestone called calcite.
Gradually the calcie builds up to form icicle-like shapes called stalactites, which hang from the roof.

Question 14

Caves and Caverns: Stalagmites

Answer 14

Drops of water may also seep through the rock and fall on the ground.
This water evaportates and leaves deposits of calcite on the floor of the cave directly below the stalactites.
The calcite builds up, forming upside-down icicle-like shapes called stalagmites.

Question 15

Caves and Caverns: Pillars

Answer 15

After thousands of years a stalactite and a stalagmite can meet and join, resulting in the formation of a pillar or column

Question 16

Factors that affect mass movement

Answer 16

Water content, water makes regolith heavier. Heavier regolith moves faster

Human activity, digging in the slope for construction will make it steeper and unstable.

Vegetation, the roots of plants and trees bind the soil together.

Animals, burrowing animals can loosen the soil. Cattle and sheep eating vegetion exposing the soil.

Question 17

Regolith

Answer 17

Weather and erosion produce loose material

Question 18

Mass movement

Answer 18

Is when regolith moves down a slope due to gravity.

Question 19

Soil Creep

Answer 19

Slow mass movement. Trees will grow at an angle, terracettes can form (steps in the ground). Walls crack and break when soil piles up behind them.

Question 20

Bog bursts

Answer 20

A bog burst, occurs when a mass of bog or peat moves down a slope after a period of heavy rainfall. The peat becomes so saturated that water can no longer soak downwards. The peat moves downslope and blocks roads and damages them aswell as buildings. It pollutes lakes and rivers.

Question 21

Mudflows

Answer 21

Muflows occur when soil and regolith become saturated with water after heavy rainfall, it moves downslope like a river of mud. They are the fastest forms of mass movement. They can also occur in the aftermath of a volcano. In snowy regions, a volcanic eruption will causes snow and ice to melt quickly. This meltwater mixes with ash, soil and rock fragments to create a dangerous kind of mudflow known as lahar.

Question 22

Landslides

Answer 22

The causes of landslides are: coastal erosion, deforestation, heavy rainfall, earthquakes and undercutting by road buildings or quarrying.

The lack of vegetation on the hillside makes the disaster much worse.

Question 23

Avalaches

Answer 23

An avalanche is the rapid movement of snow and ice downslope that is to heavy for the slope to hold.

Question 24

Controlling mass movement

Answer 24

Vegetation
Steps can be built into a mountainside to trap moving material.
Restricting overgrazing, less cowns of a farm
Controlled explosions, to trigger small avalanches making the large life threatening avalanches less likely