What’s a landform? Physical shapes of the land such as hillsides, cliffs and marshes are some examples. Landform A feature of the Earth’s surface Examples: *Lake *Stream *Valley *Canyon *Hill *Ridge *Mountain Wetland A wetland is a general term for an area characterized by a high proportion of water and watery land. * Swamp * Marsh * Bog Swamp Marsh Swamp A swamp is an area that has a high proportion of water but is dominated by trees surrounding the area. Marsh A marsh is a wetland characterized by a high proportion of water and watery land. This is an area that is dominated by grasses as opposed to trees. Hillside Cliff side photos Erosion Erosion Erosion What’s the difference between weathering & erosion? Weathering – causes rocks, boulders, etc. to split, crack or break apart, however, these rocks & particles stay in one place. Erosion – process or water or ice) of having them move (by wind Weathering! Erosion! What’s the difference between weathering & erosion? Weathering can take place in various manners: Physical or Mechanical – rocks breaking due to wind, rain, ice (natural forces) or human activity Burrowing animals or plant roots wedging rock apart Chemical – rocks change due to different chemical reactions – such as mild acid from rain deteriorates rocks, paint, or building surfaces or water & iron oxidize to become rust/oxidation. Types of Physical Weathering Frost Action Plant Action Exfoliation Abrasion Change in Temperature Plant Action • Tiny root hairs seek out small cracks and pits in rock. • Once the root hairs find a place they grow and expand. • The expansion causes great pressure and cracks the rock. Changes in Temperature As a rock is heated by the sun, its temperature can increase dramatically, and at night it cools down. As this process occurs over and over again, the bonds of the rock molecules can break, leading to cracks in the rock. These cracks then allow a path for other agents of weathering...(guesses?) Oxygen! Oxidation • Oxygen in the atmosphere chemically reacts with minerals. • ex.: rusting of a nail...this can happen with rocks too! Normal rain is at a pH of 6.2. Acid Rain! Sometimes, pollution causes the pH of rain to drop to 4. Rain with this pH level often contains Sulfur Dioxide, which forms a strong acid. When this water rains down on the earth, the acid wears away at the earth's surface...eating away at rocks and mountains and/or statues like the one below! Weathering What is Erosion? Erosion is the process by which something is detached from the surface of the earth and moved to another location. ex: When a fast moving stream picks up soil particles and moves them into a larger river basin and then from there, into the ocean, erosion has occurred! Those soil particles have moved, and thus, have helped to change the surface of the earth! Types of Erosion Water Erosion Ice Erosion Wind Erosion Gravity Erosion Deposition Deposition is when those particles or rocks have been moved and are then left in another place! Part 3: Deposition What do you see happening? Earth Processes Weathering, Erosion & Deposition have been occurring for billions of years. (These are known as Earth processes.) They can be constructive or destructive. Destructive forces break down Earth materials (such as water eroding a hill) Constructive forces build up Earth material (create landforms such as deltas from the deposition of sediments) Natural factors affect the rate of these processes - such as wind, water (rain), ice (glaciers) Positive/Negative of Erosion Positive effects of erosion – slow & steady water erosion creates lakes, rivers, hills, canyons, fertile plains. Negative effects of erosion – slow & steady water erosion can cause collapse of roads & buildings. Human activities can accelerate the Earth processes. Construction & farming are 2 activities that cause the most erosion. These activities break apart rocks. Soil & plant roots hold land in place. Sediments can also carry pollution and toxic materials (pesticides) to new areas. Positive /Negative - Deposition Positive effects of deposition – adds nutrients to soil creating fertile floodplains, building landforms such as deltas, forms rocks after long periods of time; like sandstone. Negative effects of deposition – building up & filling in rivers, lakes, wetlands, covering habitat areas needed by fish & animals, clogs pipes which provide water to cities & towns, also causes waterways to become shallow Turn and Talk! How does the earth change? Brainstorm: What is one positive impact of erosion? What is one negative impact of erosion? Topographical Maps Topographical maps show the contour or elevation of the Earth’s surface. A contour line is an imaginary line on the Earth’s surface connecting points of the same elevation. A contour interval shows the differences in elevation between adjacent contour lines. When there is a lot of space between contour lines, the land is relatively flat. When the contour lines begin to move closer together, the terrain or area is steep as indicative of mountains or hills.