23.1 Fresh Water 71% of Earth is covered with water, 3% is fresh A. Water Cycle = continuous cycling of water on Earth 1. Evaporation Sunlight heats liquid water and converts it to gas Transpiration = water released by plants 2. Condensation Water vapor cools and condenses back to liquid 3. Precipitation Water droplets or ice falls to the ground

B. Fresh Water 1. The Atmosphere Exists as water vapor or clouds Stays only a short time before precipitation 2. Streams and Rivers Rain falls Some becomes runoff = water that flows over Earth’s surface May flow into a stream or tributary, then to a river

Watershed = area of land that contributes water to a river system 3. Ponds and Lakes Usually drain into streams

4. Water beneath the surface Near surface, spaces in rock and soil are filled with air Saturated zone = where pore spaces are filled with groundwater Water table = top of the saturated zone Groundwater = form of most fresh water, water found underground within cracks and between particles of rock and soil

Permeable = rock that water can pass through (limestone, sandstone) Aquifer = permeable rock that is saturated with water Impermeable = rock that doesn’t allow water to pass (shale, granite)

5. Glaciers and Icebergs Glaciers form in areas where more snow falls than melts Weight presses snow together to form ice Weight causes flow downhill Icebergs form when glaciers break off into the ocean

23.2 Weathering and Mass Movement A. Erosion = process that wears down and carries away rock and soil Acts through weathering, gravity, streams, groundwater, glaciers, wind, waves, living things

Central park is mostly clay and does not provide good support for sky scrapers… lucky for the residents!

B. Weathering = process by which rocks are B. Weathering = process by which rocks are chemically altered or physically broken down 1. Mechanical Weathering = physically breaking rock Frost wedging = expansion when ice freezes Abrasion = scraping Plant root growth

2. Chemical Weathering = breaking down due to chemical reactions All minerals dissolve in water Rain is also slightly acidic Acid will react with minerals like calcite, limestone, marble (concrete, travertine…) Mineral is eroded, may form caves Neutralization happens which can reduce the effects of acid rain Bubbles 2HCl + CaCO3 -> CO2 + CaCl2 + H2O

Sink hole formation from chemical weathering of Calcium carbonate substrate

Formation of rust is another example of chemical weathering C. Rates of Weathering 1. Temperature Chemical weathering occurs more rapidly at high temperatures Mechanical weathering occurs more rapidly if temperatures change a lot 2. Availability of water More water, more weathering Type of rock exposed at the surface Stop here 2011-12 for CT TASK

D. Mass Movement Mass movement = downward movement of rock and soil 1. Landslides = rapid movement of large amounts of rock and soil 2. Mudflows = rapid movement of rock and soil mixed with water 3. Creep = soil gradually moves down a slope 4. Slumping = weak layers of soil or rock move down as a unit

E. Effects of Erosion 1. On-site Remove nutrients, fertilizers from soil Loss of structure and stability, loss of topsoil Change in texture and water-holding capacity 2. Off-site Prevent seed germination, bury plants Destroy roads, buildings, bridges Sedimentation could block streams and require dredging Make streams cloudy, blocking light, prevent photosynthesis Wash contaminants/pollutants into waterways, water purification problems

F. Preventing Erosion 1. Using a physical barrier to divert energy of wind or water 2. Planting vegetation, terracing, contour plowing, no-till farming, mulching Waterbreak Reforestation Mulching Windbreak Wire Fencing Terracing