Weathering And Erosion Flashcards
Shaping the Earth’s Crust
The rocks and soil of the earth’s crust are
continually being worn down because of a
number of processes.
• These processes are known collectively as
Denudation.
• Denudation occurs as a result of both
weathering and erosion.
Denudation
Denudation is caused by both weathering and erosion.
Denudation
Weathering Erosion
1. Mechanical Weathering 1. Moving water (rivers/sea)
2. Chemical Weathering 2. Moving Ice (glaciers)
3. Moving Air (wind).
Weathering
Weathering means the breakdown of rocks that are exposed to the weather.
• There are two types of weathering, Mechanical Weathering and Chemical
Weathering
Erosion
• Erosion means the breakdown of rocks and the removal of their particles.
• Erosion is caused by moving air (wind), moving water (rivers/sea), and
moving ice (glaciers).
Mechanical Weathering
Mechanical weathering breaks up the rocks into smaller
pieces.
• One type of mechanical weathering is called Freeze-
thaw action.
• Freeze-thaw action breaks the rock into smaller pieces.
• It occurs high in the mountains where there is lots of rain
and the temperature rises above and below 0 degrees
Celsius quite often.
Freeze-Thaw Action by day
During the day water seeps into joints (cracks) in the rock
Freeze thaw action by night
On cold nights when the temperature drops below freezing point the water freezes and turns to ice in doing so it expands by about 10 percent this puts stress and strain on the rock
Freeze thaw action over time
After repeated freezing and thawing the rock splits sharp jagged pieces of rock break off these pieces of rock are called screw they roll down the mountainside and build up in piles at the bottom of the slope
Chemical Weathering
• Chemical weathering dissolves rocks.
• One example of chemical weathering is called Carbonation.
• Carbonation occurs in limestone landscapes, where bare limestone
rock is exposed to the rain.
• It occurs because rainwater mixes with carbon dioxide in the
atmosphere, forming a weak carbonic acid.
• This acid reacts with calcium carbonate in the limestone, causing
the rock to slowly dissolve.
Carbonation – Karst Landscapes
Carbonation occurs in areas where bare limestone rock
is exposed to the weather.
• These areas are known as karst landscapes, after a
limestone region called Karst in Slovenia.
• An example of a Karst landscape in Ireland is the Burren
in Co. Clare.
• Here the soil has been worn away, leaving the bare
limestone rock exposed. Carbonation has created many
spectacular features, particularly underground.
Swallow hole
When streams flow onto limestone the water widens the joints and opens up bedding planes the shaft it disappears through is called a swallow hole
Clint’s
The blocks of limestone that seperate the grikes are called clints
Grikes
The cracks caused by weathering in the limestone that cause deep gashes called grikes
Mass Movement
• Mass movement means the movement of any loose
material (rocks, soil, mud) down slope under the
influence of gravity.
• The loose material is known as regolith.
• The rate of mass movement is influenced by 4 factors.
• Gradient
• Water Content
• Human Activity
• Vegetation
Influences on Mass Movement
Gradient– Mass movement occurs on sloping land. Mass
movement is fastest on steep slopes.
• Water Content– After heavy rain the regolith (loose material) is
heavier.
• Human Activity– People often cut into hillsides to make roads or
railway lines. This creates steep slopes where mass movement can
occur.
• Vegetation– The roots of trees and plants help keep the regolith
together, slowing down mass movement.
