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Properties of Water. Properties of Water. Only natural substance that exists as solid, liquid, and gas in temperatures normally found on Earth Freezing point = 0 o C (32 o F) Boiling point = 100 o C (212 o F). Properties of Water. Expands when it freezes More dense as a liquid than a solid
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Properties of Water • Only natural substance that exists as solid, liquid, and gas in temperatures normally found on Earth • Freezing point = 0oC (32oF) • Boiling point = 100oC (212oF)
Properties of Water • Expands when it freezes • More dense as a liquid than a solid • Density of water = 1 g/cm3 • Density of ice = 0.91 g/cm3
Properties of Water • High specific heat • A lot of energy is needed to change its temperature. • Moderates air temperature
Properties of Water • High surface tension • Cohesion • Adhesion
Properties of Water • Universal Solvent • Dissolves many (not all) substances
The Water Cycle • Earth’s water supply is continuously recycled. • The overall process is powered by the Sun’s energy.
Water Storage • Ocean • Most water on Earth • Glaciers • Most fresh water • Lakes • Ice/snow • Atmosphere
How Water Enters the Atmosphere • Evaporation • Transpiration • Sublimation
Forms of Precipitation • Rain • Sleet • Snow • Hail • Freezing Rain
The Water Cycle • Once water reaches Earth’s surface as precipitation, it can: • Evaporate • Infiltrate • Run off
Runoff • Runoff is water flowing downslope along Earth’s surface. • Runoff may • reach a stream, river, or lake • evaporate • accumulate and eventually seep into the ground (infiltrate)
Factors that affect Runoff • Vegetation • Rate of Precipitation • Soil Compaction • Slope
Watersheds and Divides • Watershed • all of the land area whose water drains into a stream system • stream system • large river and all its tributaries
NC Watersheds NC has 12,200 km of rivers and streams
Moving Water Carves a Path • Must have an adequate supply of water • Stream begins at headwaters
Youthful Rivers • Steep gradient (slope) • Narrow channel (downcutting) • Channel is V-shaped • Fast moving • Moves all sediment sizes • No floodplain • Rapids and waterfalls • More erosion than deposition
Mature Rivers • Channel is U-shaped • Medium velocity • Moves many sediment sizes - not boulders • Small floodplain • Meanders begin to form • Erosion and deposition occur • Carries more sediment
Old Rivers • Very shallow gradient • Channel is wider than deep • Slow moving • Moves small-sized sediments • Wide floodplain • Meanders are abundant • Large discharge
Meandering Streams • In a curve, the greatest speed is along the outside of the curve. • Erosion occurs along the outside of the curve. • Deposition occurs along the inside of the curve.
Work of Streams • A stream’s load includes all the materials that the water in a stream carries. • solution (dissolved) • suspension (carried) • bed load (pushed)
Work of Streams • Erosion • The ability of a stream to erode materials depends on its velocity. • Abrasion • Grinding • Dissolving
Lakes and Freshwater Wetlands • A lake is a depression that collects and holds water. • Reservoirs are lakes made for storing water for a community’s use.
Origins of Lakes • Natural lakes form in different ways. • Oxbow lakes: streams cut off meanders and leave isolated channels of water. • Lakes can form when stream flow becomes blocked by sediment from landslides.
Origins of Lakes • Natural lakes form in different ways. • Cirque lakes: depressions left by valley glaciers fill with water. • Kettle lakes: blocks of ice left by melting glaciers melted. • Some lakes are formed when the ceilings of limestone caverns collapse leaving depressions that fill with water.
Lakes Undergo Change • Lakes are temporary water-holding areas. • Eventually lakes fill in with sediment and become part of a new landscape.
Freshwater Wetlands • A wetland is a land area that is covered with water for a large part of the year. • Wetlands include environments commonly known as bogs, marshes, and swamps.
Freshwater Wetlands • Bogs receive their water from precipitation and tend to be rich in peat moss.
Freshwater Wetlands • Marshes frequently form along the mouths of streams and in areas with extensive deltas. • Marshes have tall grasses.
Freshwater Wetlands • Swamps are low-lying areas often located near streams. • Swamps have shrubs and trees.
Freshwater Wetlands • A filtering system • Pollutants • Sediments • Pathogenic bacteria • Habitats • Migratory birds • Water birds • Endangered species
Freshwater Wetlands • From the late 1700s to the mid 1980s, the continental United States lost 50 percent of its wetlands.