Weathering, Erosion, & Soil Test Flashcards
Weathering
The physical breakdown and chemical alteration of rock at or near Earth’s surface
Chemical Weathering
Breaks down rock components and the internal structures of minerals
The most important agent involved in chemical weathering is water (responsible for transport of ions and molecules involved in chemical processes)
Mechanical Weathering
Breaking of rocks into smaller pieces. There are 4 different kinds
Frost Wedging
Alternate freezing and thawing of water in fractures and cracks promotes the disintegration of rocks
Unloading
Exfoliation of igneous and metamorphic rocks at the Earth’s surface due to a reduction in confining pressure
Thermal Expansion:
Alternate expansion and contraction due to heating and cooling
When things are cold they expand and when things are warm they contract
Biological activity
Disintegration resulting from plants and animals
Erosion
The physical removal of material by mobile agents such as water, wind, ice, or gravity
Oxidation
Any chemical reaction in which a compound or radical loses electrons Important in decomposing ferromagnesian minerals
any chemical reaction that involves the moving of electrons
Hydrolysis
The reaction of any substance with water
Hydrogen ion attacks and replaces other positive ions
a chemical reaction or process in which a chemical compound reacts with water.
Soil
a combination of mineral and organic matter, water, and air
Regolith
(rock and mineral fragments produced by weathering) that supports the growth of plants
Parent Material
Source of the weathered mineral matter from which soil develops.
Residual soil – parent material is the underlying bedrock (was always there)
Transported soil – forms in place on parent material that has been carried from elsewhere and deposited (put somewhere) by gravity, water, wind, or ice. Like a stream bed.
Leaching
The depletion of soluble materials from the upper soil by downward–percolating water.
To pass a liquid through to carry off the soluble components.
Briefly explain how mechanical weathering aids chemical weathering.
Mechanical weathering aids chemical weathering by increasing the surface area.
Mechanical weathering increases the overall surface area when it breaks down the rock into smaller fragments.
When this happens there is more surface for chemical weathering to attack the rock, allowing chemical weathering to speed up
How does climate and a rocks characteristics affect the rate of weathering
Climate affects the rate of weathering because temperature and moisture are the most crucial factors.
Chemical weathering is most effective in areas of warm, moist climates.
A cold, dry climate will produce the lowest rate of weathering.
A warm, wet climate will produce the highest rate of weathering.
Rock characteristics also affect the rate of weathering because Rocks containing calcite (marble and limestone) readily dissolve in weakly acidic solutions. Also, silicate minerals weather in the same order as their order of crystallization. This happens because plants and bacteria grow and multiply faster in warmer temperatures.
What is meant by differential weathering
Masses of rock do not weather uniformly due to regional and local factors resulting in many unusual and spectacular rock formations and landforms.
Weathering happens at different rates to rocks in the same area. Differential weathering can shape the land by leaving peaks of highly resistant rocks and holes or depressions where less resistant rocks have been broken down.
What are the 4 basic components of soil? Remember, proportions can vary.
Soil is a combination of mineral and organic matter, water, and air.
About ½ total volume is a mixture of disintegrated & decomposed rock (mineral matter)
Humus: the decayed remains of animal & plant life (organic matter) **Plant nutrients enhance the soil’s ability to retain water. Other ½ consists of Pores spaces among the solid particles where air & water circulate. **This circulation is vital.
What is the importance of pore spaces in soil?
Soil is far from “pure” water. It is a complex solution containing soluble minerals. In the pore spaces, there will be moisture for chemical reactions that sustain life. The pores filled with moisture and air provide plants with nutrients in a form that they can use. Pore spaces that are not filled with water will have air. Air provides oxygen and CO2 that allows microorganisms and plants to live in the soil.
What is the difference between residual and transported soil?
Residual soil – parent material is the underlying bedrock
a soil material which is the result of weathering and decomposition of rocks that has not been transported from its original place.
Transported soil – forms in place on parent material that has been carried from elsewhere and deposited by gravity, water, wind, or ice. Like a stream bed.
What are 4 factors controlling soil formation? Briefly explain.
Time: Younger soils have some characteristics from their parent material, but as they age, the addition of organic matter, exposure to moisture, and other environmental factors may change its features.
Climate: The most important factor that can shape the formation of soils. Two important climatic components, temperature, and precipitation
Plants and Animals: soil’s physical and chemical properties depend on the living things (plants and animals) that live on the surface and inside the soil.
Topography: (the arrangement of the natural and artificial physical features of an area.) Variations can lead to the development of a variety of localized soil types. There will be poor soils on the steep long slopes and richer deposits at the foot of the slopes.
V/hat are the 5 horizons in a soil a profile? What horizons make up topsoil
Horizons are – zones or different layers of soil
- O horizon – organic matter
- A horizon – organic and mineral matter high biological activity.
- E horizon – little organic matter
- B horizon – zone of accumulation. In extreme cases, clay accumulation can form a very compact & impermeable layer called Hardpan.
- C horizon – partially altered parent material
Together the O and A horizons make up the topsoil
What are the 3 parts to the erosion process
- Detachment raindrop impact; kinetic energy (splash) wind loosening soil; impact
- Transportation of detached particles downhill, floating, rolling, splashing, or dragging
- Deposition (where it all deposits or lands)
What are the types of water erosion? Know the difference between them.
- Sheet-splashed soil moves uniformly
- Rill- as sheet flow becomes channels, rills are small enough to be removed by normal tillage
- Gully: runoff water becomes concentrated enough to cut deep gullies
How are sedimentation and chemical pollution harming our environment?
Sedimentation and chemical pollution. Each year in the US millions of tons of eroded soil is deposited in lakes, reservoirs, & streams. This is significant because the more sediment deposited, there is a reduction in capacity
Occasionally soil particles are contaminated with pesticides from farming.
When these chemicals are introduced to a lake or reservoir, the quality of the water becomes threatened.
Fertilizers added to soil can also make their way to rivers and streams and can create Dead Zones: excessive nutrients accelerate plant growth and leads to a depletion of Oxygen in a body of water. EX: Gulf of Mexico
The Dead Zone in the Gulf of Mexico is an area of low oxygen that can kill fish and marine life near the bottom of the sea.
