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Lecture 5

Earth Sciences
Course Code
Christine Burton

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Lecture 5 t hydrosphere
May 27, 2010
Water reservoirs
- Water on earth is found in several reservoirs: oceans, cryosphere (ice caps and glaciers),
groundwater, lakes, soils, atmosphere, rivers, and living organisms
- The average length of time that water stays in a particular reservoir is called the residence time
The hydrologic cycle
- Water constantly moves from reservoir to reservoir
- Water in ocean evaporates into the atmosphere
o It then condenses into clouds and then rain down back into the ocean or blown onto
- Water that evaporates from trees go through evapotranspiration
- Some water runs off the land and makes it back into the stream, lake, ocean
- Some water gets absorbed into the soil and becomes groundwater
- Most freshwater is tied up in ice
- Most of the tiny part of freshwater that is usable is in lakes
- }À}µóì9}(ZZ[µ(
- Trenches are found at a convergent zone where one plate is subducting under the other
- Structure:
o 2 layers:
Surface layer
x Warmer because of solar radiation
x Less dense because its warm
Deep layer
o The layers are separated by thermocline: depth interval where temperature gradient
changes the greatest
The stable layering of the ocean makes mixing between upper and deep ocean a
slow process
Ocean: Waves
- Created by wind (that is created because of solar energy)
- They develop because of the shear between the molecules of air in the wind and the molecules
of water at the surface of the sea
- Energy is transferred from the air to the water
- Tsunami also cause waves
Ocean: Tsunamis
- Usually generated by the sudden displacement of the sea floor caused by an earthquake
- Wavelengths of 100-200km; periods of 10-20min; speeds of up to 800km/h
Ocean: Tides
- Periodic tides are caused by the gravitational effects of the moon and the sun
- If earth, moon, and sun are all lined up, the gravitational effects are the highest
- If they are perpendicular, the gravitational effects are lowest
- Opposite sides of the world experience opposite tidal effects
Ocean: surface currents
- Driven by atmospheric winds
- Red circular patterns are called gyres
- Bring warm water from the equator to the poles t distributing heat
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