Weathering, Erosion and Natural Catastrophes

Weathering Weathering is the process that breaks down rock and other substances at Earth’s surface.

Erosion Erosion is the movement of rock particles by wind, water, ice, or gravity.

Working 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 Weathering There are 2 types of weathering: Mechanical and Chemical

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

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

Agents of 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.

Mechanical weathering

Ice Wedging

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

Agents 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 rain

Rates 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 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.

Erosion The material moved by erosion is sediment. When the agents of erosion lay down sediment, deposition occurs. Deposition changes the shape of the land.

Erosion

More erosion

Cycle 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 Erosion

Water The major agent of erosion Shapes Earth’s land surface

Runoff Erosion Gully Rill

Wave Erosion

River and Stream Erosion

Glacial Erosion Caused by gravity pulling glacier down

Wind 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 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.

Landslides

Mudslide

Slump

Creep

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

Volcano

Earthquake

Tornado

Hurricane

Catastrophic events can affect Earth in several 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, 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.