Test #1 Weathering and Soil: Date for Weathering and Soil Test = Jan 31st
1. Know the definitions of chemical & mechanical weathering.
Chemical weathering is a type of weathering in which rock is broken down through chemical changes.
Mechanical weathering is a type of weathering in which rock is physically broken into smaller pieces.
2. Be able to identify descriptions & examples of each type of weathering.
Mechanical Weathering
 Release of Pressure--Causes top layers of the rock to crack and flake off
 Freezing & Thawing--Water freezes causing the crack to get bigger
 Animal Actions--Animals dig, this loosens the soil & breaks apart rocks.
 Plant Root Growth--Roots grow in cracks in the rock breaking them apart
 Abrasion--Sand in wind, water, or ice can wear away rock
Chemical Weathering
 Water--most important cause of chemical weathering; dissolves rock
 Oxygen-- Rust is formed by the chemical reaction called Oxidation (H2O+O+Fe=Rust)
 Carbon Dioxide-- Dissolves soft rock underground, making caves and sinkholes, as CO2 mixes
with rainwater to produce Carbonic Acid
 Living Organisms--Roots of plants make a weak acid & dissolves rocks around the plant
 Acid Rain-- Weathers rock rapidly, especially in areas with lots of pollution
3. Know the details of the 2 factors that determine the rate of weathering.
Type of rock & Climate
4. Know descriptions of the soil profile layers and the order of the steps for soil formation.
“A” Horizon AKA “Topsoil (2nd step of soil formation)
 Humus-makes it the most fertile layer
 Plant roots grow here
 Dark colored
 Crumbly texture
 Clay & minerals
 Decomposers (worms, insects, bacteria)
“B” Horizon AKA “Subsoil” (3rd step of soil formation)
 Very little clay & humus
 Light colored
 Minerals wash down from “A” Horizon
“C” Horizon
 Partially weathered rock
Bedrock AKA “Parent Material”
 1st step in soil formation is the breaking down of bedrock to form the “C” Horizon
5. Be able to explain the importance of soil.
All living things depend on the soil. For example, we eat the animals, animals eat the grass &
plants, and plants grow in healthy soil.
6. Be able to describe the 4 soil conservation methods.
A. Contour Plowing – farmers plow along the curves of the land to prevent water from washing
away soil; rows of garden look curvy instead of straight
B. Conservation Plowing (No-Till Plowing) – farmers leave the dead plants to keep the soil covered
and in place; don’t cut down or plow old crops
C. Crop Rotation – farmers plant different crops each year that use different nutrients from the
soil
Example: (corn/cotton oats/barley/ryebeans/alfalfa)
D. Terracing – farmers plant crop on different levels on a hillside to maximize the area of usable
land and keep healthy soil in place; looks like steps on the hill
Test #2 Erosion: Date for Erosion Test = Feb 2nd
1. Know the definition & 4 agents (causes) of erosion. Know details about each.
Water—most powerful agent; creates waterfalls, meanders, oxbow lakes
Gravity—forces masses of sediment down hill; mudflows, landslides, creep, slump
Glaciers—valley glaciers create u-shaped valleys; erode by abrasion and plucking
Wind—the weakest agent of erosion, but can be powerful in shaping the land in areas where there
are few plants to hold the soil in place, e.g. the deserts. Wind erosion can cause form loess deposits
and sand dunes.
2. Define uniformitarianism.
The geological principle stating that the same processes like weathering and erosion that operate
today also operated in the past to shape and change the surface of Earth is uniformitarianism.
3. Identify the definition & 4 types of mass movement by examples.
Mass movement happens when gravity moves sediment downhill. Examples: mudflows, landslides, slump,
creep
4. Identify the types of weathering that trigger different types of erosion (HINT: they work together)
5. Know the 5 factors that affect the amount of runoff in an area.
1. The amount of rain an area receives.
2. Vegetation - grasses, shrubs & trees reduce runoff
3. Type of soil - some absorb more water than others
4. Shape of the land – steep slopes has more run-off, which causes more runoff
5. How people use the land - paved areas increase run-off, crop removal increases run-off
6. Compare & contrast valley & continental glaciers, including how glaciers form.
A glacier is any large mass of ice that moves slowly over land and form in areas where more snow
falls than melts.
Continental Glaciers--Covers Land or Continents; Spreads out over millions of square kilometers, cover
about 10% of Earth’s land, cover most of Greenland & Antarctica, in the past these have covered
larger parts of Earth – times are called Ice Ages
Valley Glaciers--Forms high in mountains when snow & ice builds up in a mountain valley; Stay
narrow& long held in by the sides of the mountain, smaller than Cont. Glaciers, form U-shaped
valleys
7. Identify the causes of soil loss.
Uncovered, loose soil can be eroded or loss by wind and water erosion.
8. Be able to categorize the effects of runoff overtime (include all of the formations from runoff to
tributaries)
Rills form gullies  gullies form streams  streams form rivers (tributaries get their water from
rivers)
9. Know the features formed by deposition of sediment by rivers.
Alluvial fans, deltas, and soil added to flood plains
10. Identify the features formed by erosion of rivers.
Water falls, flood plains, meanders, oxbow lakes
11. Explain how wind erodes rock and when sand is deposited.
Beaches, spits, sandbars, and barrier beaches,
12. Be able to compare & contrast cave formations.
Water containing carbonic acid & calcium drip from a cave’s roof forming stalactites (like icicles
hanging from the top) and stalagmites (drips the build up from the bottom of the cave floor)