Download Weathering and erosion

What breaks down rocks?
• Erosion is the process of wearing down and carrying away
rocks.
• Weathering is the process that breaks down rock and other
substances.
• Erosion works continuously to weather and carry away
rocks at Earth’s surface.
• Deposition occurs where the agents of erosion deposit, or
lay down, sediment.
• Weathering, erosion, and deposition act together in a cycle
that wears down and builds up Earth’s surface.
Types weathering
• In mechanical weathering, rock is physically
broken down into smaller pieces.
• In chemical weathering, rocks break down
through chemical changes.
Agents of mechanical weathering
• Animal actions: animals that burrow in the ground
loosen and break apart rocks in the soil.
• Freezing and thawing: Frost wedging occurs when
water freezes in cracks in rocks and expands the crack to
make it bigger.
• Plant growth: plant roots enter cracks in rocks, forcing
the rocks to crack apart when the roots grow.
Agents of mechanical weathering
• Release of pressure: As erosion removes material from
the surface of a rock, pressure is reduced, causing the
outside of the rock to crack and flake off.
• Abrasion: Sand and other rock particles that are carried
by wind, water, or ice can wear away exposed rock
surfaces like sandpaper on wood.
What type of mechanical weathering is
shown in this picture?
•release of
pressure
What type of mechanical weathering is
shown in this picture?
•freezing and
thawing
What type of mechanical weathering is
shown in this picture?
•plant growth
What type of mechanical weathering is
shown in this picture?
•animal actions
What type of mechanical weathering is
shown in this picture?
•abrasion
Agents of chemical weathering
• Water: weathers rocks by carrying substances that
dissolve or break down rock.
• Oxygen: through oxidation, iron combines with oxygen
in the presence of water to form rust, making rock soft
and crumbly.
• Carbon dioxide: when this dissolves in water, carbonic
acid forms, which easily weathers rocks like marble and
limestone.
Agents of chemical weathering
• Living organisms: as a plant’s roots grow, they produce
weak acids that slowly dissolve rock around the roots.
• Acid rain: causes very rapid chemical weathering of
rock.
What does erosion occur from?
• Water (flowing bodies such as rivers)
• Glaciers (from their movement)
• Waves (in bodies of water, with their energy coming
from the wind)
• Wind (removes surface materials)
• Mass movements (such as mudflows and landslides)
What is soil?
• The process of weathering breaks down rocks to form
sediment.
• Soil forms as a result of weathering, as rock is broken
down by weathering and mixes with other materials on
the surface.
• Soil is the loose, weathered material on Earth’s surface
in which plants can grow.
Soil composition
• Soil is a mixture of sediment, minerals, decayed
organic material, water, and air.
• One of the main ingredients of soil comes from bedrock,
which is the solid layer of rock beneath the soil. Bedrock
weathers into small particles that make up soil.
• The decayed organic material in soil is called humus,
which is a dark-colored substance that forms as plant
and animal remains decay.