Weathering Flashcards
What does endogenic mean
Within the earths surface eg plate tectonics
What does exogenic mean
At or very near the earths surface eg denudation
What is denudation
The break up of rock and removal of the broken material
Includes, weathering, erosion and mass movement
Weathering is influenced by
Rock type eg rocks with bedding planes are easier to break down
Climate influences type of weathering and speed
Topography, upland areas are more exposed to weathering
Two types of weathering
Physical (mechanical)
And chemical
What does physical weathering change
Physical appearance of rock
Two types of physical weathering
Freeze thaw (frost wedging) Exfoliation (onion weathering)
Conditions needed for freeze thaw
Adequate supply of water
Rock has pre existing fractures and joints
Temperature regularly rises and falls
How much does water expand when turning into ice
9%
What is scree
Broken material made when rock is weathered
Example of freeze thaw in Ireland
Sugarloaf Wicklow
Carrontoohil Kerry
What is diurnal temperature range
Big difference between the highest and lowest temperature
Temperatures in desert at day
40° c +
Temperatures in desert at night
0° c
Why is it so hot in the desert during the day
Lack of cloud
Lack of vegetation
Example of exfoliation
Half dome in Yosemite national park
What is chemical weathering
The decay of rocks and change in chemical makeup
Where does chemicals weathering work best
Hot, humid conditions
Two types of chemical weathering
Carbonation
Hydrolysis
What does a weak carbonic acid consist of
Rain water and carbon dioxide from atmosphere and soil
What rocks erode best
Limestone and chalk, bedding planes
Example of landscape weathered by carbonation
The burren co Clare
Marble Arch caves, Fermanagh
What does hydrolysis do to the rock
Reacts with chemical breaking in into a softer and weaker material.
Example of hydrolysis in Ireland
Leinster batholith soil
Why is hydrolysis important
Makes healthy soil
Explain freeze thaw action
Occurs when temperatures move above and below freezing Adequate rainfall Pre existing fractures 9% size increase from water to ice Expand cracks Cycle Scree
Explain exfoliation
Large diurnal temperature range Deserts (day 40° and night 0°) No clouds and lack of vegetation Rock expands when heated Contracts when cooled Outer layers heat up quicker Flakes- large slabs of scree Newly exposed outer layers - cycle continues
Darker absorb more light and different minerals cause to expand at different rates eg quartz quicker than feldspar
Explain carbonation
Rainwater absorbs carbon dioxide from atmosphere and soil
Makes a weak carbonic acid
Acid dissolves rock, changing minerals
Calcium carbonate changes to calcium bicarbonate
Sinks through rock
Mostly limestone - clints, grikes, easy access
Explain hydrolysis
Water reacts with chemicals in the rock making it softer and break down
Fine grained rock quicker to break down
Affected by temperature - every 10° increase, rate doubles
Eg Brazil rainforest 20m deep soil
Acidic water changes feldspar to kaolin. Clay like material
Feldspar was the glue that held everything together but now rock begins to crumble
Leinster batholiths
