WeatheringWeathering

The Earth’s Changing SurfaceThe Earth’s Changing Surface

WeatheringWeathering

• the process that breaks down rock and other substances at Earth’s surface

ErosionErosion

• The removal of rock particles by wind, water, ice, or gravity.

How fast can it fizz?How fast can it fizz?

• Place a “rock” into the first beaker• Crush a second “rock” and place it into the

second beaker• Add the water to the beaker with the full

rock. Time how long it takes for the “rock” to dissolve.

• Add the water to the beaker with the crushed “rock.” Time how long it takes to dissolve.

How fast can it fizz?How fast can it fizz?

• Which dissolved faster, the whole “rock” or the crushed “rock?”

• What variable affected how long it took each of them to dissolve?

Two Types of WeatheringTwo Types of Weathering

Mechanical

Chemical

Mechanical WeatheringMechanical Weathering

• Rock is physically broken into smaller pieces.– These rocks have the same composition as

the rocks they came from.

Causes of Mechanical WeatheringCauses of Mechanical Weathering

• Ice wedging – freezing and thawing– Causes potholes on streets

Causes of Mechanical WeatheringCauses of Mechanical Weathering

• Release of pressure - erosion removes material from surface, pressure is reduced. Pressure release causes rock to crack.

Causes of Mechanical WeatheringCauses of Mechanical Weathering

• Plant growth – roots of trees and other plants enter cracks in rocks.

Cause of Mechanical WeatheringCause of Mechanical Weathering

• Actions of animals – animals that burrow in the ground loosen and break apart rocks in the soil.

Cause of Mechanical Weathering Cause of Mechanical Weathering

• Abrasion – the grinding away of rock by rock particles carried by water, ice, wind, or gravity.

Chemical WeatheringChemical Weathering

• The process that breaks down rock through chemical changes.– Produces new minerals.

Cause of Chemical WeatheringCause of Chemical Weathering

• Water – dissolves rock– Water is the most important cause of chemical

weathering

Cause of Chemical WeatheringCause of Chemical Weathering

• Oxygen – rust!! – Iron combines with oxygen in the presence of

water in a process called oxidation

Cause of Chemical WeatheringCause of Chemical Weathering

• Carbon Dioxide – dissolves in rain water– Easily weathers rocks such as marble and

limestone

Cause of Chemical WeatheringCause of Chemical Weathering

• Living Organisms – plants produce weak acids

Cause of Chemical WeatheringCause of Chemical Weathering

• Acid Rain – how is it formed?– Coal, oil, and gas is burned for energy– These fuels pollute the air with sulfur, carbon,

and nitrogen– These compounds react with rainwater,

forming acid rain.

Walk!!Walk!!

• Re-visit the stops on our previous walk

Rate of WeatheringRate of Weathering

• Type of Rock– The minerals that make up rock determine

how fast it weathers. • Marble vs. granite

• Climate– Faster in wet climates– Chemical reactions occur faster at higher

temperatures