3.2 Processes That Shape the Earth
ESS1 - The earth and earth materials as we know them today have developed over long
periods of time, through continual change processes.
Explain how earth events (abruptly and over time) can bring about changes in Earth’s surface:
landforms, ocean floor, rock features, or climate.
Students demonstrate an understanding of processes and change over time within earth
systems by
3a evaluating slow processes (e.g. weathering, erosion, mountain building, to determine how the
earth has changed and will continue to change over time.
3b evaluating fast processes (e.g. erosion, volcanoes and earthquakes) to determine how the
earth has changed and will continue to change over time.
3c investigating the effect of flowing water on landforms (e.g. stream table, local environment).
Vocabulary - Text: Prentice Hall’s Earth’s Changing Surface (page number)
unless Inside Earth text, then (IE page number) .
SLOW Processes that cause the Earth to change over time:
1. weathering Chemical and physical processes that break down rock at Earth’s
surface (39).
Note: As weathering breaks apart rock into smaller and smaller pieces,
the surface area exposed to weathering increases (42)
Type of weathering where rock is physically broken into smaller pieces

mechanical (40).
Causes:
weathering
 freezing & thawing
Ice wedging – water freezes in crack in rock; it expands and
makes crack bigger. Process also causes cracks in sidewalks
and potholes in streets (40).
 release of pressure
Erosion removes material from surface of a mass of rock and
pressure on rock is reduced. Release of pressure causes
outside of rock to flake off like layers of an onion (40).
 plant growth
Roots enter cracks in rocks, grow and force the cracks farther
apart or even pry them apart (41).
 actions of animals
Burrowing animals like gophers and some insects – loosen
and break apart rocks in the soil (40).
 abrasion – grinding away of rock by rock particles carried by
water, ice wind or gravity.
Sand and other rock particles carried by wind, water, or ice
wear away exposed rock surfaces like sandpaper on wood
(41).
 chemical
weathering
Type of weathering where rock breaks down from exposure to water
and atmospheric gases (CO2, O2, and H2O vapor).
Causes:
 action of water
Most important cause of chemical weathering. Dissolves
rock (43).
 oxygen
oxidation - iron combines with oxygen in the presence of
water.
This causes rust. Rock that contains iron also rusts then
crumbles apart. It is red/brown (43).
 carbon dioxide
Dissolves in rainwater forming carbonic acid that seeps into
the soil. Easily weathers rocks like limestone and marble
(43).
 living organisms
Lichens (plant-like organism) and roots of plants produce
weak acids that slowly dissolve the rock around the roots
(43).
 acid rain
Burning coal, oil and gas over past 150yrs has put sulfur,
carbon and nitrogen compounds into the air. They react
chemically with water vapor in clouds forming acids. These
acids mix with raindrops and fall as acid rain. Acid rain
causes very rapid chemical weathering.
RATE of The most important factors that determine how fast weathering occurs
weathering are:
 type of rock
Minerals that make up the rock determine how fast it
weathers.
If minerals dissolve slowly in water, rock weathers
slowly.
If minerals dissolve quickly in water, rock weathers
quickly.
permeable – material is full of tiny connected air spaces that
allow water to seep through it.
Some rock weathers more quickly because it is permeable.
It weathers chemically at a faster rate because water easily
seeps into it, dissolves it and removes the material (44).
 climate – refers to the average weather conditions in an area.
Chemical and mechanical weathering occur faster in wet
climates.
Rainfall provides water needed for chemical changes and
physical changes (freezing and thawing) (44).
High temperatures - Chemical reactions occur more
quickly.
2. erosion
Process by which natural forces or agents (wind, water, ice, or gravity)
move weathered rock and soil from one place to another (39).
 sediment – material moved by erosion (pieces of rock, soil,
plant, animal)
 deposition – occurs where agents of erosion deposit sediment
and changes the shape of the land(67).
→Erosion Cycle 1. Erosion wears down land. 2. Deposition
fills up hollows. 3. New mountains form which are eroded. This
erosion cycle is continuous because the forces of erosion and
deposition do not stop.
Process of erosion caused by (66):
 gravity – force that moves rock and other materials downhill
causing mass movement(67).
Types of mass movement (SLOW or FAST Process):
landslides – occurs when rock and soil slide quickly down
a steep slope; most destructive (68)
mudflows – a rapid downhill movement of a mixture of
water, rock, and soil (68).
slump – a mass of rock and soil suddenly slips down a
slope in one large mass (often when water soaks bottom
of clay soil) (68).

creep – very slow downhill movement of rock and soil
(often from freezing and thawing of water in cracked
layers of rock beneath the soil (69).
running water
Moving water is major agent of erosion that has shaped
Earth’s land surface (73). Raindrops can loosen soil and carry
the particles.
runoff – water that runs over the Earth’s surface.
Forms: rills → gullies (channel with water only after it
rains) → streams → rivers → lake or ocean (75)
rivers – through erosion, rivers can create a variety of
features:
valleys – elongated low area between hills formed by a
stream
waterfalls – occurs or forms where a river meets rock
that erodes slowly (like granite) and then flows over
softer rock downstream.
floodplains – flat, wide area of land along river.
Lower down on its course where land slopes gently,
river spreads out forming a river valley. Floodplains
are here.
meanders – loop-like bend in the river (S end
Mississippi)
oxbow lakes – meander that has been cut off from the
river(76).
During flood, high water finds a straighter pass
downstream. As water falls, sediments dam up the
ends of a meander.
 glaciers – any large mass of ice that moves slowly over land
(a few cm to a few meters per year)(92).
Form only where more snow falls than melts (93).
When snow & ice get 30-40m deep, gravity pulls glacier
downhill
continental glaciers – glacier that covers much of a continent
Flow in all directions as they move (like pancake batter in
frying pan)
In distant past – covered one third of Earth’s land
Have advanced, retreated (last time - 10,000 yrs ago), or
melted back, several times.
valley glaciers – long, narrow glacier that forms when snow
and ice buildup high in a mountain valley.
Sides of mountain keep them from spreading out in all
directions.
Usually move down valleys already cut by rivers.
Much smaller than continental glaciers
Processes of glacial erosion:
plucking – glacier picks up rocks as it flows over land; rock
fragments & boulders freeze to glacier bottom and
are carried.
abrasion – many rocks remain on bottom and get dragged
along. Gouges and scratches bedrock.
Glacial deposition (building up)
When a glacier melts, everything it picked up is deposited
(94).
Landforms:
till – mixture of sediments (sand, silt, clay,
boulders)deposited directly on surface
moraine – till deposited at edges of a glacier form a ridge
(Long Island, NY)
kettle – depression formed when ice is left in glacial till.
When ice melts, kettle remains forming ponds or
kettle lakes.
 waves - form from wind that blows across the water’s surface
Shape the coast through erosion by breaking down
rock and transporting sand and other sediment (97).
impact - large waves hit rocks with force & break apart
rocks
abrasion – wave in shallow water picks up sediment that
hits land where it wears away at rock

Landforms created by wave erosion:
headland – part of shore sticks out into ocean
Made of hard rock that resists erosion longer
sea arch
sea cave
sea stack
wave cut cliff
Deposits by waves:
beach
longshore drift – waves repeatedly hit beach, beach
sediment moves down beach with current
spit – beach that projects out like a finger
result of longshore process
sandbar – long ridges of sand parallel to the shore
barrier beaches – form when storm waves pile up large
amounts of sand forming a long, narrow island
parallel to the coast
wind –
Causes erosion by (101):
deflation – process where wind removes surface
materials (102)
abrasion – may polish rocks but causes little erosion;
Deposition (building up) form:
sand dunes (103)
loess deposits – very fine sediment made up of silt and
clay so it travels far
Note: Weathering and erosion work together continuously to wear down and carry away
rocks at the Earth’s surface (39).
Note: Weathering, erosion and deposition act together in a cycle that wears down and
builds up the Earth’s surface (67). As a mountain wears down in one place, new
landforms build up in other places. The cycle is never-ending.
3. mountain
building
Process that thrusts rock up to the surface of the Earth (39).
Over millions of years, fault movement can change a flat plain into a
towering mountain range.
Text: Prentice Hall’s Inside Earth (Ch2Sec1)



crust – a layer of rock that forms Earth’s outer skin (p21) (Ill.p22)
 lithosphere – outer layer of crust, rigid
 Crust composition: O, Ca, Si, Al, Fe, Na, K, Mg
plate- section of lithosphere that slowly moves carrying the crust.
fault – a break in Earth’s crust where slabs of crust slip past each
other.
o The rocks on both sides of a fault can move up or sideways.
o Where do they occur?
 Along plate boundaries where forces of plate motion
compress, pull, or shear (cut) the crust so much that the crust
breaks.
Mountains can form by:
1) A fault-block mountain Normal fault lifts a block of rock ← →
(p58)
2) folding – rock is stressed by compression and may bend slowly
without breaking (p59 Fig 8)
Note: Erosion Cycle:
1. Erosion wears down land.
2. Deposition fills up hollows.
3. New mountains or plateaus form, which are eroded.
This is continuous because the forces of erosion and deposition don’t stop.