Download Rocks and Weathering

Changing Earth’s Surface
What Processes Break Down Rock?
Table of Contents 3.1
Rocks and Weathering
Ms. De Los Rios
6th Grade
Vocabulary 3.1
1. Erosion is the process by which water, ice, wind, or gravity moves weathered
particles of rock and soil.
2. Sediment- Small, solid pieces of material that come from rocks or the remains of
organisms; earth materials deposited by erosion.
3. Deposition- Process in which sediment is laid down in new locations.
4. Mechanical Weathering- The type of weathering in which rock is physically
broken into smaller pieces.
5. Chemical Weathering- The process that breaks down rock through chemical
changes.
6. Abrasion- The grinding away of rock by other rock particles carried in water, ice,
or wind.
7. Frost Wedging- Process that splits rock when water seeps into cracks, then
freezes and expands.
8. Oxidation- A chemical change in which a substance combine with oxygen as
when iron oxidizes, forming rust.
9. Permeable- Characteristic of a material that contains connected air spaces or
pores, that water can seep through easily.
What Processes Wear Down and Build Up
Earth’s Surface? Pg. 92
Weathering is the process that breaks down rock and
other substances.
Erosion is the process by which natural forces move
weathered rock and soil from one place to another.
What are agents or erosion??
And NO, not agent 007!!! 
Gravity, moving water, glaciers, waves, and wind
The material that gets carried away by erosion is
called sediment.
What makes up sediment??
pieces of rock or soil, or the remains of plants and
animals.
Rocks and Weathering pg. 93
Cycle of Erosion and Deposition
What are the steps in the cycle of erosion and deposition?
What Processes Wear Down and Build Up
Earth’s Surface? Pg. 93
Deposition occurs where the agents of erosion deposit, or lay
down, sediment. Deposition changes the shape of the land.
Weathering, erosion, and deposition act together in
a cycle that wears down and builds up Earth’s surface.
Erosion and deposition are at work
everywhere on Earth.
As a mountains wears down in one place,
new landform builds up in other places!
The cycle of erosion and deposition is
never-ending.
What Causes Weathering? Pg. 94
Physical weathering
a type of weathering in which rock is
physically broken into smaller pieces
Types of Physical
weathering
•Animal actions
•Freezing and thawing
•Plant growth
•Release and pressure
•Abrasion
These are the natural agents
of physical weathering
Two types of weathering:
Mechanical W.
Physical W.
Mechanical Weathering pg. 94
Actions of
animals
Animals burrow
in the groundmoles, gophers,
prairie dogs and
some insects.
Loosen the soil
and break soil
apart
Freezing and
thawing,
Plant growth
Release of
pressure
Abrasion
Water seeps into
cracks in rocks and
freezes and
expands. The ice
forces the rock
apart. Wedges of ice
in rocks widen and
deepen cracks in the
process called frost
wedging.
Plant roots enter
cracks in rocks. As
roots grow, they
force the cracks
apart. Even small
plant root can pry
apart cracked
roots
Erosion removes material
from the surface of a mass
of rock pressure, pressure
on the rock is reduced.
The released of pressure
causes the outside of the
rock to crack and flake off
like the layers of onion.
Abrasion refers
to the wearing
away of rock by
rock particles
carried by
water, ice, wind,
or gravity.
What Causes Weathering? Pg. 96
r. 1 P
Chemical weathering
A process that breaks down rock
through chemical changes.
Types of Chemical weathering
•Water
•Oxygen
•Carbon Dioxide
•Living organisms
•Acid rain
These are the agents of chemical
weathering.
For example, the oxygen gas in air
combines with iron in the presence of
water in a process called oxidation.
•The product of oxidation is rust.
•Rust makes rock soft and crumbly.
Rocks and Weathering pg.96
Weathering and Surface Area
The diagram shows what would happen if a rock cube broke into
smaller cubes.
Figure 2
By how much does the surface
area increase? How would the
rate of weathering change?
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Agents of Chemical Weathering pg. 97
Oxygen-
Carbon Dioxide-
Living
organisms-
Acid rain-
the oxygen gas in air
combines with iron in
the presence of water
in a process called
oxidation. The
product of oxidation is
rust. Rust makes rock
soft and crumbly.
Another gas found in
the air, that causes
chemical weathering
when it dissolves in
water. The result is a
weak acid called
carbonic acid. C. A.
easily weathers some
kinds of rocks, such
as marble and
limestone.
as plants roots grow,
they produce weak
acids that slowly
dissolve rock around
the roots. Lichensplantlike organisms
that grow on rocksalso produce weak
acids.
Rainwater is naturally acidic.
Burning coal, oil and gas for
energy can pollute the air with
sulfur, carbon, and nitrogen
compounds. These
compounds react with water
vapor in clouds, making acids
that are stronger than normal
rainwater. These acids mix
with raindrops and fall as acid
rain. Acid rain causes rapid
chemical weathering of rock.
The Old Man of the Mountain
The Old Man of the
Mountain was a rock
formation in New
Hampshire that looked like
a face. But it collapsed
suddenly on May 3, 2003.
Mechanical and chemical
weathering wore away rock
behind the “chin” of the
face, causing the whole
face to fall.
How Fast Does Weathering Occur? Pg. 98
The most important factors that determine the rate at
which weathering occurs are the type of rock and climate.
•Some rocks weather more easily because they are permeable.
Permeable means that a material is full of tiny, connected air
spaces that allow water to seep through it.
•Climate refers to the average weather conditions in an area.
•Both mechanical w. & physical w. occur faster in wet climates.
•Rainfall= chemical changes & freezing and thawing
•Human activities= producing more acid rain, increase rate of
weathering.
Rocks and Weathering
Forces of _______________Weathering