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True or False: The Earth’s surface has stayed the same for thousands of years True or False: The Earth’s surface has stayed the same for thousands of years The Earth’s surface is always changing! Earth’s Changing Surface Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface Weathering – Breaks down Deposition – deposits / builds Erosion moves - Weathering The breakdown of Earth’s crust into smaller pieces. Must occur before erosion can happen No movement usually occurs. Sediments- naturally occurring material that is broken down by processes of weathering; small/tiny pieces of rock Physical/Mechanical Weathering the process of breaking down Earth’s surface into smaller pieces – similar to a physical change Physical Weathering -- The steep walls here were carved out by moving water Palo Duro Canyon in the High Plains Eco-Region 1.Water 2.Ice 3.Wind 4.Gravity 5.Organisms Causes of Physical Weathering Enchanted Rock in the Llano Uplift Eco-region Exfoliation-warming and cooling of rocks over time causes rocks to peel into sheets Chemical Weathering Chemical weathering occurs when chemical reactions dissolve the minerals in rocks or changes them into different minerals (rusting, acid breakdown, etc) This cave was formed by slightly acidic water dissolving the limestone Causes of Chemical Weathering Natural Bridge Caverns in Texas 1.Oxidation 2.Hydration 3.Carbonation Let’s compare Please draw a Venn diagram and compare chemical and physical weathering. How are they similar/different? Water causes weathering What evidence of weathering do you see in this picture? Wind causes weathering Why wasn’t this mass of land weathered away? What evidence of weathering do you see in this picture? Ice causes weathering Describe how ice causes weathering? Erosion The process by which water, ice, wind or gravity move sediments. What evidence of erosion do you see in this picture? Erosion is Movement of Sediment! • Erosion is the process by which weathered rock and soil (sediment) are moved from one place to another. • Erosion carves the Earth's surface creating canyons, gorges, and even beaches. What do you think has caused this rock to look this way? Erosion is Movement of Sediment! The intensity of erosion is determined by the 4 S’s: • • • • Sum (amount) Speed Slope Surface Wind Erosion • As the wind blows it picks up small particles of sand/sediment and blasts large rocks with the abrasive particles, cutting and shaping the rock. Wind Erosion Water causes Erosion When rain falls to the Earth it can evaporate, sink into the ground, or flow over the land as Runoff. When it flows over land, erosion occurs. Runoff picks up pieces of rock and "runs" downhill cutting tiny grooves (called rills) into the land. Water Causes Erosion • runoff, rivers, and streams Water causes Erosion How much erosion takes place is determined by the: • Sum (amount) • Slope • Speed • Surface Can you act increasing and decreasing the four S’s? Ice Causes Erosion Glaciers wear down the landscape; by picking up and carrying debris that moves across the land along with the ice. Ice Causes Erosion Glaciers can pick up and carry sediment that ranges in size from sand grains to boulders bigger than houses. Moving like a conveyor belt and a bulldozer, a single glacier can move millions of tons of material! Ice Causes Erosion How much erosion takes place is determined by the: • **Sum (Glaciers are massive!) • Slope • Speed • Surface Gravity causes Erosion Gravity is the force that moves rock and other materials downhill. Gravity causes erosion Creep, Slump, Landslides, Mudslides, and Avalanches. Slower Faster These are examples of mass movement landslide clip.mpeg (or called mass wasting) Gravity causes Erosion How much erosion takes place is determined by the: • Sum • **Slope • Speed • **Surface Bare Slopes vs. Vegetation Stabilized Slopes How do weathering, erosion and depostion impact each side of the “hill”? Bare Slopes vs. Vegetation Stabilized Slopes • Mudslide danger • Loss of topsoil • Clogged storm drains • Flooding problems • Expensive clean up • Eroded or buried house foundations Bare Slopes vs. Vegetation Stabilized Slopes • Mudslide danger • Loss of topsoil • Clogged storm drains • Flooding problems • Expensive clean up • Eroded or buried house foundations • Soil in place • Less clean up • Minimum erosion • Protection for house foundations Plants CAN CAUSE weathering Plants CAN PREVENT erosion Erosion Galveston Texas before/after Hurricane Ike Deposition Deposition is the process by which sediments are deposited in new locations. • Together, Erosion and Deposition build new landforms. Delta Soil and dirt carried by these rivers is deposited at the mouth (where rivers meet the ocean), and new land is formed. The new, soil-rich land is known as a Delta Canyons This simple animation provides you with a visualization of how the Colorado River has "downcut" into the rock layers of the Grand Canyon. Canyons are large valleys created by a river or stream. How long it took to carve the Grand Canyon is debated by geologists. Some estimates are between 6 and 8 million years, which is very recent by comparison. Meanders Meandering streams wander side to side as they constantly seek out the lowest elevation. This constant motion creates a series of S-shaped “loops”. Meanders - Extra Info Stream Velocity varies from one side to the other side of the “S”, resulting in erosion in some places and deposition of sediments in others. Floodplains • Floodplains are an area of land that is prone to flooding. • These are low-lying areas along the sides of a river channel that have regular times of heavy waterflow to cause the river to spill over and flood the land. WED Look at the picture of Galveston above, what do you think will happen to this land if another hurricane hits the Galveston coast? Explain each component and how will the island be effected.