Weathering and Erosion formation of landforms weathering and

Weathering and Erosion formation of landforms

weathering and erosion • The process of weathering and erosion are the main forces behind landscape types. • However, they are not the only reason for a plain, plateau, or a mountain region to form. ▫ Other factors such as glaciations and tectonic activity lead to landscape building.

weathering • Weathering is the chemical and physical processes that change the characteristics of rocks on the Earth’s surface. • It is also known as the preparation for erosion. In order for weathering to occur, the environment of a rock sample must change and the rock needs to be exposed to some form of water and/or the air. • Human processes such as pollution, which can be a large factor in acid rain, along with the acts of other living organisms, can cause chemical weathering to occur at faster rates.

weathering process • The weathering process occurs when rocks are exposed to the hydrosphere (water) and atmosphere (air). • These weathering agents can change the physical and chemical characteristics of rocks. • As rocks are broken down (weathered) they can be classified as different types of sediments, which are: boulders, cobbles, pebbles, sand, silt, clay, and colloids.

physical weathering • Types of Physical weathering ▫ ▫ ▫ Frost heaving and Frost wedging Plant roots Friction and impact Burrowing of animals Temperature changes

physical weathering Frost heaving • Frost heave is the result of pressure created from a combination of freezing temperatures and soil defrosting. The fluctuating freezing and thawing conditions heave, or lift, the soil, which is often characterized by deep cracking of the soil. Plants may be uprooted from the ground as well. Frost wedging • • Frost wedging is caused by the repeated freeze-thaw cycle of water in extreme climates. Most rocks have small cracks in them, called joints. When it rains, rainwater seeps into these joints. As the day cools and temperatures at night drop below freezing, the water inside the joints freezes. As water freezes into ice, it expands. The expanding ice places pressure on the joints in the rock. Finally, when the pressure is too much, the joint expands. In some cases, the rock will split, though this usually happens after repeated freeze and thaws. As new water is added during the warmer days, more ice is created at night, wedging the joints apart further.

physical weathering Plant roots Friction and impact • The roots of large plants can penetrate the rocky soil and break it apart. • Constant exposure to friction and impact can change the formation of the rocks and cause them to break off.

physical weathering Animals Temperature changes • Animals that burrow into rocks can cause weathering. • The changing temperatures can alter landscapes by causing the soil to freeze or burn.

weathering cycle

erosion • Erosion is the removal of solids (sediment, soil, rock and other particles) in the natural environment. It usually occurs due to transport by: ▫ wind, water, or ice ▫ down-slope creep of soil and other material under the force of gravity ▫ living organisms, such as burrowing animals • Erosion is a noticeable intrinsic natural process but in many places it is increased by human land use. • Poor land use practices include: ▫ deforestation ▫ overgrazing ▫ unmanaged construction activity ▫ road-building.

erosion • Land that is used for the production of agricultural crops generally experiences a significant greater rate of erosion that of land under natural vegetation. • However, improved land use practices can limit erosion, using techniques such as terrace-building, conservation tillage practices, and tree planting. • A certain amount of erosion is natural and, in fact, healthy for the ecosystem. For example, gravels continuously move downstream in watercourses. • Excessive erosion, however, does cause problems, such as receiving water sedimentation, ecosystem damage and outright loss of soil.

erosion landforms These are some examples of landforms that have formed as a result of the erosion process: Arete: • a steep-sided, sharp-edged bedrock ridge formed by two glaciers eroding away on opposite sides of the ridge. Cirque: • a semicircular or amphitheater-shaped bedrock feature created as glaciers scour back into the mountain. This is where the snow and ice forming the glacier first accumulates; it is the "headwaters" of a glacier.

erosion landforms Col • a low spot or pass along a cirque. Groove • an elongate depression carved out of bedrock as numerous rock particles embedded in the base of a glacier scour away at the underlying bedrock as the ice flows across the landscape.

erosion landforms Horn • a pyramid-shaped mountain peak created by several glaciers eroding away at different sides of the same mountain. Paternoster Lakes • a chain of lakes in a glacial valley.

erosion landforms Striations • lines etched in bedrock underlying glaciers as individual particles embedded in the glacier scratch the underlying bedrock. These lines indicate the orientation of glacial flow. U-shaped Valley • a glacially eroded valley; also called a glacial trough.

conclusion • In conclusion, the effects of weathering and erosion occur naturally but are sometimes sped up by human processes. • Weathering and erosion are the cause of many of the land forms that you see around you every day. • Understanding these phenomenon can help us better understand the world around us and how it was made, and how it will continue to be shaped by these processes.