Chapter 7: Weathering, Erosion and Soil

the process by which rocks on or near earth’s surface breakdown or change

the removal and transport of weathered material from one location to another

mechanical weathering
the type of weathering by which rocks and minerals break down into smaller pieces

physical weathering
mechanical weathering is also called

temperature and pressure
these are the two major factors of mechanical weathering

Frozen water takes up __% more space than liquid water

frost wedging
the repeated thawing and freezing of water in the cracks of rocks

the process by which outer rock layers are stripped away

chemical weathering
the process by which rocks and minerals undergo changes in their composition as the result of chemical reactions

agents of chemical weathering include: water, oxygen, carbon dioxide and ______

the rate of chemical weathering reactions doubles with each __°C increase in temperature

the reaction of water with other substances

the chemical reaction of oxygen with other substances

the percent of earth’s atmosphere which is oxygen gas

carbon dioxide
this atmospheric gas contributes to the chemical weathering process by combining with water and forming carbonic acid

climate, rock type and composition, surface area and topography and other variables
the variables which effect the rate of weathering

chemical weathering
this type of weathering occurs in climates with warm temperatures, abundant rainfall and lush vegetation

mechanical weathering
this type of weathering occurs in cool, dry climates

this rock type is the most susceptible to weathering processes

temperature, precipitation
the interaction between __________ and ____________ has the greatest effect on a region’s rate of weathering

when materials are dropped in a location in a process known as this, the final stage in the erosional process

this force is associated with many erosional agents, because this force tends to pull all materials downslope

rill erosion
the erosion by running water in small channels, on the side of a slope

gully erosion
when a channel becomes deep and wide it can evolve into this type of erosion, gullies can be more than 3m deep

ocean waves, wind
coastal areas undergo erosion by ____________ and ______

when a river enters a large body of water, such as the ocean, the water slows down and deposits large amounts of sediments, forming these

gravity, running water, glaciers and wind
agents of erosion

a major erosional agent in areas with limited precipitation and high temperatures

erode by scraping, gouging and picking up large rock and debris piles

the loose covering of broken rock particles and decaying organic matter, called humus, overlying the bedrock of earth’s surface

parent bedrock
the solid bedrock from which weathered pieces of rock first break off

residual soil
soil located above its parent material

transported soil
soil that has been moved from its parent bedrock to another location

soil profile
the vertical sequence of soil layers

soil horizon
a distinct layer, or zone, within a soil profile

A, B and C
the three major soil horizons

high concentrations of organic matter and humus are found in this soil horizon (soils rich in humus are usually dark coloured)

organic, dark material remaining after decomposition of living organisms

this soil horizon contains subsoils that are enriched with clay minerals

this soil horizon is directly above the bedrock and contains weathered parent material

this soil horizon commonly has a zone of accumulation consisting of soluble minerals that have been washed out from the topsoil, the horizon may be red or brown in colour due to the presence of iron oxides

in the B soil horizon this hard material is commonly found, which may be so dense that it doesn’t allow much water through it

dependant on the region, this effects the thickness of the developing soil

slopes facing this direction receive more direct sunlight and have somewhat thicker soils that slopes facing in other directions

which has more fertile soils valleys or slopes

desert, polar, temperate and tropical
the four major types of soil (alphabetical)

polar soils
these soils form at high altitudes and high elevations such as Greenland, Canada and Antartica, the soil has good drainage but no distinct horizons because they are very shallow

permanently frozen ground

temperate soils
these soils vary greatly and are able to support such diverse environments as forests, grasslands and prairies

desert soils
these soils receive low levels of precipitation, as a result they often have accumulated salts and can support only a limited amount of vegetation

tropical soils
these soils experience high temperatures and heavy rainfall, leading to intensely weathered and often infertile soil

particles of soil are classified according to this

the smallest particle of soil

the largest particle of soil

soil fertility
the measure of how well a soil can support the growth of plants

composition, climate
a soil’s ___________ and the _______ in which it developed are the main factors that determine a soil’s colour

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