Weathering, Erosion and Weathering, Erosion and Natural CatastrophesNatural Catastrophes

WeatheringWeathering• Weathering is the process that

breaks down rock and other substances at Earth’s surface.

ErosionErosion• Erosion is the movement of rock

particles by wind, water, ice, or gravity.

Working togetherWorking together

Weathering and erosion work together continuously to wear down and carry away the rocks at Earth’s surface. Weathering breaks rock down and erosion carries it away.

2 Types of Weathering2 Types of Weathering

• There are 2 types of weathering:

• Mechanical and Chemical

Working togetherWorking together

• As mechanical weathering breaks rock into pieces, more surface area becomes exposed to chemical weathering. So, they also work together.

Mechanical WeatheringMechanical Weathering

• The type of weathering in which rock is physically broken into smaller pieces is called mechanical weathering.

• Freezing and thawing

• Release of pressure

• Action of animals

• Growth of plants

• Abrasion - rock particles carried by wind, water, ice and gravity.

• Water expands when it freezes, and acts as a wedge.

• This process is called ice wedging.

Agents of mechanical weathering

Mechanical weatheringMechanical weathering

Ice WedgingIce Wedging

Chemical WeatheringChemical Weathering

• Chemical weathering is the process that breaks down rock through chemical changes.

Agents of chemical weatheringAgents of chemical weathering

The agents of chemical weathering include:

• water

• Oxygen (oxidation is a reaction w/ O2)

• carbon dioxide ( carbonic acid)

• living organisms( plant roots produce weak acids)

• acid rain

Weathering from acid rainWeathering from acid rain

Rates of weatheringRates of weathering

• The most important factors that determine the rate at which weathering occurs are the type of rock and climate.

• Ex: Some rock weathers easily because it is permeable, which means that it is full of air spaces that water gets through.

Chemical weatheringChemical weathering• Water is the most important agent of chemical

weathering. • Water weathers rock by dissolving it. • The oxygen in air is an important cause of

chemical weathering. • Plant roots produce weak acids that slowly

dissolve any rock around the roots. • Lichens also produce a weak acid that weathers

rock.• Acid rain causes very rapid chemical

weathering.

ErosionErosion• The material moved by erosion is

sediment.

• When the agents of erosion lay down sediment, deposition occurs. – Deposition changes the shape of the land.

ErosionErosion

More erosionMore erosion

Cycle of erosionCycle of erosion

• 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. Sometimes, they work slowly. At other times, they work more quickly.

Agents of ErosionAgents of Erosion

WaterWater

• The major agent of erosion

• Shapes Earth’s land surface

Runoff ErosionRunoff Erosion

Rill

Gully

Wave ErosionWave Erosion

River and Stream ErosionRiver and Stream Erosion

Glacial ErosionGlacial Erosion

Caused by gravity pulling glacier down

Wind ErosionWind Erosion•Wind itself is the weakest cause of erosion.

•Greatest impact is on an area that has few plants to hold dry soil in place

• Gravity is the force that moves rock and other materials downhill.

• Gravity causes mass movement, any one of several processes that move sediment downhill.

• Mass movement can be rapid or slow.

Mass MovementsMass Movements

The different types of mass movement include:

• Landslides – rock and soil slide quickly down a steep slope.

• Mudslides -the rapid movement of a mixture of water, rock, and soil.

• Slump – a mass of rock and soil suddenly slips down a slope in one large mass.

• Creep – very slow downhill movement of rock and soil.

LandslidesLandslides

MudslideMudslide

SlumpSlump

CreepCreep

Natural catastrophesNatural catastrophes

• A natural catastrophe/hazard is an event that results from Earth processes and that can cause damage and endanger human life.

And the natural catastrophes are…And the natural catastrophes are…

• droughts• wildfires• floods• the different types of mass movement• tsunamis • hurricanes • tornadoes• earthquakes • volcanoes• other storms

VolcanoVolcano

EarthquakeEarthquake

TornadoTornado

HurricaneHurricane

Catastrophic events can affect Earth in Catastrophic events can affect Earth in

several waysseveral ways. .

• Catastrophic events that result from surface processes may speed up erosion and deposition.

• Catastrophic events resulting from processes inside Earth change the crust itself (volcanoes).

People, People, PeoplePeople, People, People

• Where people locate their activities can increase the damaging effects of natural hazards.

• How people use land also alters Earth systems in ways that may cause catastrophic events.