weathering (6) Flashcards
Weathering
The disintegration and decomposition of rock at or near the surface of Earth
Mechanical Weathering
The physical disintegration of rock, resulting in smaller fragments
Chemical Weathering
The processes by which the internal structure of a mineral is altered by the removal and/or addition of elements
Erosion
The incorporation and transportation of material by a mobile agent, such as water, wind or ice
Frost wedging
The mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices
Joint
A fracture in rock along which there has been no movement
Sheeting
A mechanical weathering process that is characterized by the splitting off of slab like sheets of rock
Exfoliation Dome
A large, dome-shaped structure, usually composed of granite, that is formed by sheeting
Dissolution
The process of dissolving into a homogenous solution, as when an acidic solution dissolves limestone; a common form of chemical weathering
Oxidation
The removal of one or more electrons from an atom or ion. So named because elements commonly combine with oxygen
Hydrolysis
A chemical weathering process in which minerals are altered by chemically reacting with water and acids
Sheroidal Weathering
Any weathering process that tends to produce a spherical shape from any initially blocky shape
How is carbonic acid formed in nature?
When it rains
What occurs when carbonic acid reacts with calcite-rich rocks such as limestone?
Dissolution
What products result when carbonic acid reacts with potassium feldspar?
Clay-Kaolinite
List several minerals that are especially susceptible to oxidation and list two common products of oxidation.
Ferromagnesian silica, biotite, pyroxene, etc.
Rust, hematite and limonite
Differential Weathering
The variation in the rate and degree of weathering caused by such factors as mineral makeup, degree of jointing, and climate
Explain why granite and marble headstones weather differently.
Composition
Marble is made of calcite which is really susceptible to dissolution
How does climate influence weathering?
Fastest weathering occurs in areas that are warm and wet
Regolith
The layer of rock and mineral fragments that nearly everywhere covers Earth’s land surface
Soil
A combination of mineral and organic matter, water, and air; the portion of the regolith that supports plant growth
Humus
Organic matter in soil that is produced by the decomposition of plants and animals
Soil Texture
The relative proportions of clay, silt, and sand in a soil. A soil’s texture strongly influences its ability to retain and transmit water and air
Explain why soil is considered an interface in the Earth system.
Geosphere, Atmosphere, Hydrosphere, and the Biosphere come together
Why is texture an important soil property for agriculture?
Ideal soils need to be in between in properties of holding water
Parent Material
The material on which a soil develops
List the 5 basic controls of soil formation.
Parent Material Time Climate Biology Topography
Which factor is the most influential in soil formation?
Climate
How might the direction a slope is facing influence soil formation?
In the North, South facing slopes get a lot more sun than north facing slopes
Horizons
Layers in a soil profile
Soil Profile
A vertical section through a soil, showing its succession of horizons and the underlying parent material
Eluviation
The washing out of fine soil components from the A horizon by downward-percolating water
Leaching
The depletion of soluble materials from the upper soil by downward-percolating water
Zone of Accumulation
The accumulation of fine clay particles to enhance the B horizon’s ability to hold water
Hardpan
When clay accumulation forms a very compact impermeable layer
Why are soils classified?
So that we can know what each soil is good for
Soil Taxonomy
A soil classification system that consists of six hierarchical categories, based on observable soil characteristics. This system recognizes 12 soil orders.
Why are soils in tropical rain forests not well suited for intensive farming?
Very little humus
Place these phenomena in proper sequence: sheet erosion, gullies, raindrop impact, rills, stream.
Raindrop impact, sheet erosion, rills, gullies, stream
Explain how human activities have affected the rate of soil erosion.
Deforestation
