Weathering and Erosion Chapter 19 Section 4

Objectives Identify the causes of rock shaping due to weathering and erosion Explain how chemical weathering can form underground caves in limestone Describe how acid rain affects the landscape

Key Terms Erosion Deposition Acid rain

Physical Weathering Also called Mechanical Weathering Breaks rocks into smaller pieces and eventually becomes soil Ice can break rocks In a process called frost wedging, water fills in cracks in the rock and splits it apart when it expands during freezing Plants can break rocks The roots or other parts of plants can grow into the cracks between rock and split it apart as it grows larger

Chemical Weathering Chemical weathering takes longer and is based on several chemical reactions Rusting reactions Iron oxides or rust cause a red color to the land Think Mars! Carbon Dioxide CO2 dissolved in rainwater can “eat away” limestone underground and cause caves to form Acid Rain Air pollution can dissolve in rain water and fall to Earth causing rock to “melt” and lakes and rivers to be polluted

Erosion The removal and transportation of weathered and non-weathered materials by: Running water Wind Waves Ice Underground water Gravity

Water Erosion Fast moving water can dissolve and carry away sediments, (small pieces of broken rock material) When the water slows down, the larger sediments will fall out of the stream of water and become part of the riverbed, (deposited there until the water flow increases) Huge amounts of sediment encircle our continent, (we see them as beaches)

Sea Erosion Sediments can be washed away by ocean waves Rocks may be put in place to stop this erosion process Even rocks can be eroded by fast moving water or powerful waves The type of rock determines how fast erosion occurs, (sandstone faster than igneous rock)

Glacier Erosion Ice can move tremendous amounts of rock and soil. The ice can scrape the landscape and remove everything down to the bedrock Melt water from glaciers may carry sediments away from the glacier When the glacier melts away, there may be a different landscape after than what was there before

Wind Erosion Wind can reshape the landscape Wind can carry sediments like water can… The faster the wind, the heavier the particles The particles strike objects in their way and can cause erosion at the surface Sand and other particles, (dust), may be transported and deposited many miles from their source, (like sand dunes on a larger scale)

Summary Physical weathering breaks down rock by: Water erosion, ice wedging, wind abrasion, and glacial abrasion, (there are other forces also0 In chemical weathering, rock is altered by chemical reactions between water and minerals, causing a breakdown of the rock Carbonic Acid acts as a weathering agent and is responsible for the formation of limestone caves

Summary Acid rain can weather rock and harm living organisms. It is the by-product of fossil fuel emissions, (smog), reacting with water in the atmosphere