Presentation on theme: "Water Erosion and Deposition Surface Water 8.1. I.Runoff A.Runoff – water that doesn’t soak into the ground or evaporate. B.Factors Affecting Runoff a.Amount."— Presentation transcript:
I.Runoff A.Runoff – water that doesn’t soak into the ground or evaporate. B.Factors Affecting Runoff a.Amount of Rain i.Light rain has time to soak in. b.Length of Time c.Slope of Land i.On steep slopes, gravity causes water to runoff before it can soak in or evaporate. d.Amount of Vegetation i.Water will runoff areas with little or no vegetation.
C.The Effects of Gravity a.Water falling down a slope picks up speed, and causes erosion much quicker than slow- moving water. D.Water Erosion a.Water will wear a path as it travels down a slope time after time. E.Rill and Gully Erosion a.Rill Erosion – small stream erodes plants and soils and leaves a small scar. b.Gully Erosion – a rill channel that becomes broader and deeper to form a gully
F.Sheet Erosion a.Sheet Erosion – rainwater flows into lower elevations, carrying sediments with it. G.Stream Erosion a.Water can continue to flow in low elevations, carrying sediments, causing erosion. II.River System Development A.River System a.Water runoff joins small streams, and larger streams form. b.When larger streams join together they form rivers.
B.Drainage Basins a.Drainage Basins – Land area from which a stream gets its water. b.All water in a river system eventually flows to the same location c.The largest drainage basin in the US is the Mississippi River drainage basin. III.Stages of Stream Development A.Rivers are classified as young, mature, or old. B.Classification is based on movement, not on actual age.
C.Young Streams a.Flow down steep slopes b.May have waterfalls, and whitewater rapids c.Has high energy and erodes the stream bottom more than its sides. D.Mature Streams a.Flows less swiftly b.Most of the rocks that cause waterfalls and rapids have been eroded away. c.Erodes more on the sides d.Forms curves because the speeds of the water changes. e.Shallow water moves slowly due to friction f.Meander – curves formed by faster moving water.
g.Floodplain – broad, flat valley floor carved by a meandering stream E.Old Streams a.Flows slowly through a broad, flat floodplain F.Too Much Water a.Rivers can overflow over their banks b.Dams and levees are built to stop flooding
IV.Deposition by Surface Water A.When water looses energy it will drop sediments. B.Delta – triangular or fan-shaped deposit formed as sediments are deposited as water empties into an ocean, gulf, or lake. C.Alluvial fan – deposit created when water empties from a mountain valley onto a flat open plain. Pg 225 1-4
I.Groundwater System Development A.Soil is made of many small rock fragments, with weathered rock underneath. B.Space between the fragments and pieces of weathered rock are called pores. C.Groundwater – water that soaks into the ground and collects in pores.
D.Permeability a.Groundwater system is similar to a river system. b.Water travels via connected pores. c.Permeable – water is able to pass through pores i.Sandstone is permeable d.Impermeable – water cannot pass through i.Clay is impermeable
E.Groundwater Movement a.Groundwater will continue going down until it reaches an impermeable layer. b.It will then fill up all of the open pores in the permeable layer above. c.Aquifer – layer of permeable rock that lets water move freely. d.Water table – upper surface of the zone of saturation. II.Water Table A.Average person uses 80-100 gallons of water per day.
B.Wells a.Goes deep into the zone of saturation b.Pumps bring it to the surface c.If the water table drops, because of a dry season, then a well can go dry d.Rainfall or an increase in groundwater is needed to raise the water table e.Too much water being pumped can lead to land sink f.Artisan well is a well that does not require a pump. i.Sloping aquifer forces water to rise from pressure ii.Less common than other wells
C.Springs a.Spring – where the water table meets the Earth’s surface and flows out. b.Used as a source of fresh water c.Can be hot when rocks in contact with the water are heated by the molten material under the surface. D.Geysers a.Geyser – hot spring that erupts periodically, shooting water and steam into the air. b.Groundwater is heated causing it to expand c.Remaining water boils quickly turning into steam. d.Steam erupts forcing the remaining water out with it.
III.Groundwater Erosion and Deposition A.Water mixes with CO 2 to create a weak acid. B.Acid can dissolve rock, specifically limestone. C.Cave – cracks in limestone are enlarged until an underground opening is formed. D.Cave Formation a.Stalactites form when water evaporates from the ceiling of a cave leaving behind a deposit of calcite.
E.Sinkholes a.Forms when underground rock is dissolved near the surface. Pg. 223 1-3
Water Erosion and Deposition 8.3 Ocean Shoreline
I.The Shore A.Shoreline is where the land meets the ocean. B.Shoreline Forces a.Surface waves and tides move sediments back and forth, constantly eroding and depositing sediments. b.Longshore current – water current that runs parallel to the shore, along the beach i.Carries metric tons of sediment and acts like rivers of sand in the ocean. ii.Uses extra energy to erode more shoreline sediments.
II.Rocky Shorelines A.Waves wear around rock to form hollows and eventually caves. B.When too much erosion occurs, overhanging rock may fall into the ocean. C.Rock fragments are ground up by the endless motion of waves and transported as sediment by the longshore current.
D.Soft rocks are eroded before harder rocks leaving islands of harder rocks. III.Sandy Beaches A.Beaches – deposits of sediments that run parallel to the shore B.They stretch inland as far as tides and waves can deposit sediment C.Made of many different materials a.Pebbles, sand, and seashells b.Quartz c.Hawaii’s black sands – basalt d.Green sands – olivine e.Jamaica's white sands – coral and shell fragments
IV.Sand Erosion and Deposition A.Eroded by longshore currents, wind, and storms. B.Easily damaged by storms and human activities C.Barrier Islands a.Barrier Islands – sand deposits that parallel but are separated by the mainland b.Start underwater, and are added to by hurricanes and storms. c.Once exposed, wind blows loose sand into dunes. Pg. 237 1-3