Term 3 Physical Geography Flashcards
What is Physical Geography?
- Weathering
- erosion
- Deposition
- Land forms
What is Weathering?
The breaking down of rock into small particles by:
- Physical processes
- Chemical processes
- Biological processes
What is Erosion?
The process by which weathered material is removed from the earth’s surface by agents like:
- Water (rivers, waves)
- Wind
- Ice (glaciers)
What is Deposition?
The laying down of solid material in the form of sediment
What is Physical Weathering?
The breakdown of rocks into smaller fragments through processes, such as:
- expansion
- contraction mainly due to temperature changes
- occurs in areas where there is a large daily temperature range, hot in the day and cold at night
What are the two types of Physical Weathering?
- Freeze - thaw weathering (frost shattering)
- Thermal fracturing
What is Freeze and thaw weathering?
- Water becomes trapped in a crack in the rock
- If the air temperature drops below freezing the water will freeze and expand
- If the temperature rises the ice melts
- These processes repeat and the rock weakens
- Takes place in cold places
What is Thermal Fracturing?
- Where there are large differences between day and night temperature
- Outer layers of the rock peels off.
- The process is called exfoliation
- Fires can also cause exfoliation
- Exfoliation with chemical weathering causes spheroidal weathering
What is pressure released (unloading)?
- Is also a form of physical weathering without changes in temperature.
- When rocks such as granite which forms within the earth crust are exposed by erosion these rocks were subjected to great pressure when buried under other rocks. They expand and fracture when pressure is released, causing layers to separate (exfoliation)
What is chemical weathering?
Some minerals especially limestone compounds are dissolved out of rocks by rainwater. The rocks begin to break-up
What are the features of chemical weathering?
- Limestone pavement
- Grikes
- Clints
- Limestone caves
- Honeycomb weathering
Where does chemical weathering occur?
- In warm regions with high rainfall
- example: Equatorial regions (25 N S)
What is Biological weathering?
- Is caused by living organisms
- example:
- roots of plants
- small animals that dig
What is honeycomb weathering?
- This is caused by different minerals in the rock decomposing at different rates
- The minerals with the faster chemical reaction break down first, leaving small holes in the rock
What are the impact of human activities on weathering?
-Humans greatly increase the rates of weathering specifically chemical weathering through pollution
-Gases like carbon dioxide, Sulphur dioxide and nitrogen oxide causes acid rain
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What are the three phases of a river (or stadia)?
- Upper course (young)
- Middle course (adult)
- Bottom course (old)
What is the Upper course (Young stage) of a river?
- The river starts here
- The valley has a deep V shape
- Lots of friction
- The flow is turbulent
- The main process is vertical erosion
- The river has a lot of energy
- Waterfalls and rapids often occur
- The incline is steep
- Interlocking spurs
What is the Middle course (Adult stage) of a river?
- Wider valley
- Less friction
- Volume is bigger
- River flows faster but less turbulent
- The main process is lateral erosion
- The river starts forming meanders
- The incline is less
- River cliffs
What is the Lower course (Old phase) of a river?
- Valley becomes flatter
- Volume is the largest
- Carries a large load
- The river flows over a floodplain
- Main process is deposition
- River flows in large meanders
- Ox bow lakes are formed
What is a Floodplain?
- Broad flat piece of land that surrounds the river
- Formed by erosion and deposition
- Fertile soil
What is an Ox-bow lake?
- The necks of the meanders become narrower
- The two outer bends meet
- River cuts through the neck
- The isolated meander is an ox-bow lake
Sea
Waves change a coastline constantly
- Can make a coastline retract due to erosion
- Can make a coastline due to deposition
What is wave erosion?
-It is the greatest where waves break at the base of a cliff
What is deposition?
-A feature of deposition is a beach
