Chapter 7: Weathering, Erosion and Soil

weathering
the process by which rocks on or near earth’s surface breakdown or change
erosion
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
9
Frozen water takes up __% more space than liquid water
frost wedging
the repeated thawing and freezing of water in the cracks of rocks
exfoliation
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
acids
agents of chemical weathering include: water, oxygen, carbon dioxide and ______
10
the rate of chemical weathering reactions doubles with each __°C increase in temperature
hydrolysis
the reaction of water with other substances
oxidation
the chemical reaction of oxygen with other substances
21
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
sedimentary
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
deposition
when materials are dropped in a location in a process known as this, the final stage in the erosional process
gravity
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 ______
deltas
deltas
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
wind
a major erosional agent in areas with limited precipitation and high temperatures
glaciers
erode by scraping, gouging and picking up large rock and debris piles
soil
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
A
high concentrations of organic matter and humus are found in this soil horizon (soils rich in humus are usually dark coloured)
humus
organic, dark material remaining after decomposition of living organisms
B
this soil horizon contains subsoils that are enriched with clay minerals
C
this soil horizon is directly above the bedrock and contains weathered parent material
B
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
hardpan
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
topography
dependant on the region, this effects the thickness of the developing soil
south
slopes facing this direction receive more direct sunlight and have somewhat thicker soils that slopes facing in other directions
slopes
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
permafrost
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
size
particles of soil are classified according to this
clay
the smallest particle of soil
sand
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