A. Altering the Landscape
a. Weathering—processes that alter rock on or near
the earth’s surface.
b. Can change landscapes over time and create soil
for plant life.
c. Sediment—mud, sand, silt created by weathering
B. Mechanical Weathering
a. Mechanical weathering—processes that break
rock into smaller pieces.
b. Does not change rock’s composition, only size .
c. Examples: frost, plant roots, road construction,
C. Chemical Weathering
1. Chemical weathering—interaction of elements
creates new substance.
a. Example: when iron rusts it reacts to oxygen in
air and crumbles.
2. Warm, moist climates produce more chemical
weathering than cool, dry.
Making Comparisons: Why would chemical
weathering be rare in a desert area?
Chemical weathering usually occurs where
water is present. Desert areas have little
A. Weathered Material Moves
1. Erosion—when weathered material moves by
winds, water, ice, gravity.
a. movement grinds rock into smaller pieces,
carries to new location.
b. Example: water carries topsoil from hill to
river, river narrows.
B. Water Erosion
1. Most streams erode vertically and horizontally .
a. A valley cut by a stream gets deeper, wider;
forms v-shaped valley
b. a river deposits sediment at ocean, creates
delta—fan-like landform (Δ Greek letter
Movement: A view of the Colorado River and the
Grand Canyon in Arizona. The canyon’s depth was
created by water erosion, and the width by rain and
C. Wind Erosion
1. Wind transports sediment from one place to another.
2. Loess (LOH.uhs) wind-blown silt and clay
sediment; produces fertile soil.
C. Glacial Erosion
1. Glacier—large, long-lasting mass of ice; forms in
2. Glaciation—changing of landforms by slowly
a. Example: cutting u-shaped valleys in land.
3. Moraine—hill or ridge formed by rocks deposited
Movement: At Chakachamna in Alaska, a glacier
moves down a mountain.
has the glacier
had on the
III. Building Soil
A. Soil Formation
1. Soil—loose mix of weathered rock, organic
matter, air, water.
2. Soil supports plant growth; fertility is dependent
on three factors:
b. amount of humus, which is organic material in
c. amount of air and water.
B. Soil Factors
1. When geographers study soil, they look at five
a. parent material—the chemical composition of
the original rock.
b. relief—the steeper the slope, the greater
erosion; less soil made.
c. organisms—plants, worms, ants, bacteria
loosen soil; supply nutrients.
d. climate—hot, cold, wet, dry climates produce
e. time—about 2.5 cubic cm. of soil produced