Forces that shape our earthPresentation Transcript
Forces That Shape Our Earth: Weathering And Erosion
Weathering & Erosion: Erosion and weathering are major forces that shape Earth’s surface. For example, the Grand Canyon was formed through erosion by the Colorado River running through it!
What is weathering?Weathering: The breaking down of rocks into smaller pieces.1. Mechanical /Physical2. Chemical Hulk Rock Smash!
So what is erosion?Erosion: The movement of weathered rock by wind, water, glaciers & gravity
Types of Weathering:Mechanical/Physical: Rock is physically broken into smaller pieces (larger pieces become smaller pieces of the same rock)Chemical: Rock is chemically changed (like rusting or dissolving away)
5 Agents of Mechanical Weathering:1. Release of Pressure2. Freezing & Thawing3. Animal Actions4. Plant Growth5. Abrasion
Release of Pressure As the surface of a rock is eroded, the rock begins to release pressure Causes top layers of the rock to crack and flake off
Release of pressure: rock cracks like an egg shell
Freezing & ThawingWhen water in the cracks of rocks freezes it expands causing the crack to enlarge or get bigger. The ice melts & refreezes over & over, breaking the rock apart.
Result of Freezing & Thawing
Animal ActionsAnimals dig (burrow) through the ground to make their homes. This loosens the soil & breaks apart rocks.
Plant Root GrowthPlants roots can grow into cracks in the rock, slowly breaking them apart.
Abrasion Sand and other rock particles in wind, water or ice can wear away exposed rock surfaces. Like sandblasting or sandpaper on wood
Chemical WeatheringThe process that breaks down the surface of rock by chemical changes.
5 Agents of Chemical Weathering1. Water2. Oxygen3. Carbon Dioxide4. Living Organisms5. Acid Rain
WaterWater dissolves rockWater is the most important cause of chemical weathering
Oxygen Oxygen + Water + Iron = Rust through the Chemical reaction called Oxidation Rock will become crumbly, soft, and appear reddish-brown in color
Rusted rock on hillside
Carbon DioxideCO2 + rainwater = Carbonic AcidCarbonic Acid weathers softer rock like limestone & marble as it seeps into spaces in rock.Ex: sinkholes, caves
Living OrganismsThe roots of plants make a weak acid that slowly dissolves rocks around the plant.
Lichens grow on rock
Acid RainAcid rain causes rocks to weather very rapidly.