Earth science weathering and erosion notes
Weathering & Erosion
Weathering is the process that produces change in the surface of rocks exposed to the atmosphere and/or hydrosphere.
Physical weathering is breaking rock by force. ex: hitting, scratching, cracking
Frost action (AKA ice wedging)-
Water seeps into small cracks in rocks.
When the water freezes it expands creating great pressure.
The crack widens and allows water to seep deeper into the rock.
(Robert Frost’s Mending Wall makes a reference to a frost heave.)
Plant action
Tiny root hairs seek out small cracks and pits in rock.
Once the root hairs find a place they grow and expand.
The expansion causes great pressure and cracks the rock.
Exfoliation
Rocks formed deep in the Earth are made under high pressure.
When the pressure is released the rocks expand & crack.
May also be caused by alternate heating and cooling of rocks by weather conditions.
Abrasion- rubbing by other rocks.
Chemical weathering is where the rock material is changed into another substance by reacting with a chemical.
Oxidation
Oxygen in the atmosphere chemically reacts with minerals. ex.: rusting of a nail
Water (hydrolysis)
Minerals are dissolved in water. ex.: Halite, calcite
Acid
Carbonic acid:
C02 dissolves in rain water forming a weak acid (seltzer).
Acid Rain: Sulfur Dioxide in the atmosphere dissolves in rain water forming a strong acid (sulfuric acid).
Rates of weathering will be influenced by...
Surface area exposed - weathering occurs on the surface. The more surface exposed, the faster the weathering will occur.
Mineral composition- some minerals are more resistant than others. ex.:Quartz is resistant to chemical and physical weathering.
In the diagram above the different layers of the rock are weathered at different rates depending on the minerals within the rock. The layers sticking up most are the most resistant.
Climatic Conditions:
Cold and/or dry climates favor physical weathering.
Warm and wet
Weathering is the process that produces change in the surface of rocks exposed to the atmosphere and/or hydrosphere.
Physical weathering is breaking rock by force. ex: hitting, scratching, cracking
Frost action (AKA ice wedging)-
Water seeps into small cracks in rocks.
When the water freezes it expands creating great pressure.
The crack widens and allows water to seep deeper into the rock.
(Robert Frost’s Mending Wall makes a reference to a frost heave.)
Plant action
Tiny root hairs seek out small cracks and pits in rock.
Once the root hairs find a place they grow and expand.
The expansion causes great pressure and cracks the rock.
Exfoliation
Rocks formed deep in the Earth are made under high pressure.
When the pressure is released the rocks expand & crack.
May also be caused by alternate heating and cooling of rocks by weather conditions.
Abrasion- rubbing by other rocks.
Chemical weathering is where the rock material is changed into another substance by reacting with a chemical.
Oxidation
Oxygen in the atmosphere chemically reacts with minerals. ex.: rusting of a nail
Water (hydrolysis)
Minerals are dissolved in water. ex.: Halite, calcite
Acid
Carbonic acid:
C02 dissolves in rain water forming a weak acid (seltzer).
Acid Rain: Sulfur Dioxide in the atmosphere dissolves in rain water forming a strong acid (sulfuric acid).
Rates of weathering will be influenced by...
Surface area exposed - weathering occurs on the surface. The more surface exposed, the faster the weathering will occur.
Mineral composition- some minerals are more resistant than others. ex.:Quartz is resistant to chemical and physical weathering.
In the diagram above the different layers of the rock are weathered at different rates depending on the minerals within the rock. The layers sticking up most are the most resistant.
Climatic Conditions:
Cold and/or dry climates favor physical weathering.
Warm and wet