Download
1 / 61
610 likes | 615 Vues
WEATHERING. Two types of Weathering. Mechanical - when rocks are broken apart by a physical process. This does not change the make up of the material. Chemical - when chemical reactions dissolve the minerals in rocks, or changes them into different minerals. Mechanical Weathering.
E N D
Two types of Weathering • Mechanical- when rocks are broken apart by a physical process. This does not change the make up of the material. • Chemical- when chemical reactions dissolve the minerals in rocks, or changes them into different minerals.
Once mechanical weathering breaks down the rocks, more and more surface area is exposed, and then more areas get weathered. This speeds up the process of the weathering. weathering
Once the “acid rain” falls… • It dissolves the minerals in the rock • This changes the rock and breaks it down • Eventually it turns into a clay like substance in the end called kaolinite • This is a common in some soils (like Georgia) • The clay is an end product of weathering
What else can the acid do? • Acid damages man-made structures as well; limestone, marble, and sandstone are susceptible to damage from acid deposition, as are metals, paints, textiles and ceramics. Repairing the damage caused by acid rain to buildings and monuments costs millions of dollars per year.
Many Caves are a result of chemical weathering • The carbonic acid wears away at calcite, the main mineral in limestone • This causes the rock to change form and shape, and over thousands of years it causes caves to form in spectacular ways • The erosion or weathering causes the minerals to breakdown into liquid form, and then slowly solidifies causing stalagmites and stalactites.
Plants can also produce acid from their roots and when they decay. • This will dissolve minerals in rock and weaken the rock • Eventually the rock will break into smaller pieces, and the process speeds up.
Another major factor in chemical weathering is oxygen • Oxygen aides in the process of weathering by means of oxidation • When metallic materials are exposed to oxygen and water for long periods of time, a rusting takes place, just like a chain on a bike.
Climate matters too! • Hot and cold DRY areas have less chemical weathering, and are more prone to mechanical weathering. • Warm WET climate promotes chemical weathering because of increased exposure to the rain.
Finally, • The type of rock affects the rate that weathering takes place. • Some rocks weather faster than others, and the type of climate affects different types of rocks differently. • When rocks weather and break down, this is the beginning of the formation of soil.
Erosion and Deposition
What is Erosion?? • Erosion is the movement of rocks, sediment, and/or soil. • The main agents of erosion are wind, water, ice, and gravity.
What is Deposition? • Deposition is simply where sediments stop moving, or are deposited. • Deposition is responsible for the build up of land formations.
WIND EROSION • Wind erosion can happen from heavy winds or mild winds. • Mild winds do not have much effect on the landscape, but heavy winds can form Loess’ and Sand Dunes
Water Erosion • Anything from a light rain, to rivers and the oceans can cause erosion by water. • Water’s erosive power has shaped much of the earth’s landscape. • Major areas of beauty such as the Grand Canyon have been shaped by water erosion.
Erosion by Ice or Glacier • Glaciers are large sections of ice that can be the size of entire continents. • Glaciers used to cover much of earth’s surface during ice ages; now about 10 percent of earth’s land is covered by glaciers (Antarctica and Greenland). • Many glaciers move very slowly, and as they do, they carry sediment with them.
Evidence of past Glaciers • Many glaciers are valley glaciers, and are sometimes referred to as “Ice Rivers.” • As these glaciers move and cut their way through the valleys, they leave a “U” shape behind. U shaped valleys are evidence of past glaciers.
