Ch.6 Weathering and Erosion Flashcards
Weathering
the process of rocks, minerals, and other materials breaking down or dissolving on Earth’s surface.
Types of weathering
-Mechanical
- Chemical
-Spheroidal
Mechanical weathering
Caused by…
-freeze-thaw
-unloading/exfoliation
-growth of crystals
-thermal expansion/contraction
-wetting/drying
-root wedging
-burrowing animals
freeze-thaw
occurs when rocks are porous or permeable. Water enters weaknesses in the rock; water freezes and expands, causing the weakness to widen. When the ice melts, it only makes its way deeper into the cracks. The cycle continues.
Unloading
removing the weight of overlying rock, which releases pressure on the rock below
Exfoliation
The process by which the outer layers of a rock break away from the rest of the rock, often in parallel layer
Root wedging
a natural process that occurs when plant roots grow into cracks in rocks and widen them over time
Chemical weathering
the erosion or disintegration of rocks, building materials, etc caused by rain water reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts.
Types of chemical weathering
- hydrolysis
- oxidation
- carbonation
- hydration
- ion exchange
Hydrolysis
The breakdown of chemical bonds of a mineral due to the introduction of water
Oxidation
Oxygen reacting with metal elements in a rock, creating oxides
Carbonation reactions
Mixing of water with CO2 to create carbonic acid, which dissolves/breaks down minerals within the rock
Hydration reactions
Addition of water molecules to a substance without breaking them apart. Nothing new is essentially created nor broken
Ion-Exchange reactions
these generally involve the substitution of loosely bonded ions absorbed onto mineral surfaces
Spheroidal Weathering
A type of chemical weathering that causes the formation of concentric layers of decayed rock around a corestone
