Diff Geo Unit 5

Chapter 9 pages 211-213 and Chapter 15 pages 392-407

CHAPTER 9PAGES 211-213

Surface Water Movement

• Earth’s water supply is recycled in a continuous process called the water cycle

• Water falls as precipitation• Water heats up and moves back into the

atmosphere as evaporation or transpiration• Water soaks into the ground or runs off into

larger bodies of water

The Water Cycle

Water molecule paths vary

• A water molecule may spend time within a living organism

• It may be trapped in a snowfield, glacier, lake or ocean

• The overall process of the water cycle is one of repeated evaporation and condensation powered by the sun’s energy

Runoff

• Water falls to the surface in the form of rain, snow, sleet, or hail

• Once water reaches the surface it may be absorbed into the ground or flow down the surface

• This downward flow is runoff

5 Conditions

• 1. Porosity• If water is to seep into the ground, there needs

to be pores where it can fit• This is found in loose soil• If there is no where for the water to enter, then

it will remain on the surface or run downhill if possible

• It will either find a body of water or it will eventually evaporate

2. Vegetation

• The more vegetation in the soil, the more opportunity for water to be absorbed

• The more vegetation, the less erosion caused by rain

• The looser the soil, the better for absorption

3. Rate of Precipitation

• If the rate of precipitation exceed the rate of infiltration into the ground, then run off will occur

• So the lighter and longer the precip is better than a quick downpour

• Less erosion• More absorption

4. Soil Composition

• Decayed organic matter in soil is called humus• Minerals in the soil come in different sizes• They are classified as either sand, silt, or clay• The larger the particles, the more places to

water to enter and the faster it moves

5. Slope

• The steeper the slope of land, the faster the water flows downhill

• There is also a greater potential for erosion with a steep slope

CHAPTER 15PAGES 392-40797% of water on earth is salt water3% is freshwater

Chemical Properties of Seawater

• Salinity is the measure of the amount of salt dissolved in the water

• Measured in parts per thousand (ppt)• The average content is 35 ppt or 3.5 %• Dissolved gases are oxygen, nitrogen, and

carbon dioxide• Dissolved nutrients are nitrates, phosphates,

and silicates

Variations in Salinity

• In hotter, subtropical zones, the rate of evaporation is greater than average

• Therefore the salt content here is a little greater than average

• In equatorial regions where it rains a lot more than average, the salinity here is a little lower

• Melting glaciers lower the Salinity & raises sea level

Sources of Sea Salt

• Marine organisms absorb magnesium in their calcium carbonate shells based on the salinity of the water

• The amount found in ancient fossils matches the amount found today

• The ions in the water came from volcanic gases of chlorine and sulfur dioxide

• Weather and erosion of crustal rocks also

Removal of Sea Salts

• Although salt ions are continuously added to the ocean, the salinity does not increase

• Salts are precipitated from the water• Salt spray is picked up by wind and deposited

on land• Marine organisms use salt to build their shells,

bones, and teeth

Physical Properties of Seawater

• Seawater behaves differently than freshwater• The density of seawater is about 1.02g/cm3

• This is due to colder temperatures and salt content

• Therefore, the freezing point is less than freshwater and the density is greater

• This means it needs to be much colder for the water to freeze when salt is added

Absorption of Light

• The deeper, the less light absorbed• Light penetrates only the upper 100m• This is the only area where there is enough

light for photosynthesis to occur

Ocean Layering

• The average surface temp is 15C• Temps decrease significantly with depth• Under the surface layer is the thermocline,

where temp drops quickly• The bottom layer is cold and dark• This is caused by density differences in the

water based on temp

Typical Ocean Temp Profile

• Ocean surface temps are warmer in equatorial regions and very cold in polar regions

• In polar seas, the thermocline and surface layer are absent in polar seas (high latitudes)

Water Masses

• The ocean water is constantly moving from polar regions to equatorial and vice versa

• This circulates the different temps and densities of water around the globe

• 3 masses in the Atlantic Ocean:• 1. Antarctic bottom water- coldest and

densest• 2. north Atlantic deep water- warmer and less

dense and overrides #1• 3. Antarctic intermediate water- is the least

dense and most warm, and overrides both #1 and #2

Ocean Movements

• A typical ocean wave has a crest at the highest point and a trough at the lowest

• Wavelength is from crest to crest• The wave base is the half the wavelength• Wavelength determines speed of the wave

• Wave height depends on 3 factors:• 1. wind speed• 2. wind duration• 3. fetch- where the wind blows from

• Breaking waves (breakers) occur in shallow water near the shore

• Here the waves lose energy due to friction with the bottom

Tides

• Tides are the periodic rise and fall of sea level• High tide, low tide• Tidal range varies based on topography and

latitude• The greater the latitude, the greater the range

Causes of Tides

• Tides are caused by gravitational attraction among the Earth, the Moon, and the Sun

• Even though the moon is much smaller than the sun, lunar tides are more than twice as large

• Solar tides either enhance or somewhat diminish lunar tides

• New and Full Moon• Spring tides: high and low tides are greater

than normal• At this time the sun, the moon, and the earth

are all aligned

• 1st & 3rd Quarter Moon• Neap tides: high tides and low tides are less

than normal• At this time the sun, moon, and earth form a

right angle

Ocean Currents

• Density currents are caused by differences in temperature and salinity of ocean water

• Density currents move slowly in deep ocean waters

• Surface currents are wind driven• They affect the upper few hundred meters of

the ocean• Tropical winds blow east to west, so the

currents do too (NH)• The prevailing westerlies cause the currents to

move west to east (NH)• The polar winds push the currents east to

west (NH)

Gyres

• Closed circular currents caused by deflection from the continents

• There are 5 gyres:• 1. North Pacific• 2. North Atlantic• 3. South Pacific• 4. South Atlantic• 5. Indian Ocean

• Due to the Coriolis Effect, the gyres in the NH circulate in a clockwise direction and vice versa in the SH

• A well known warm current is the Kuroshio or Japan Current

• Warm currents circulate towards the polar regions cooler circulate towards equatorial regions

Upwelling

• The ocean doesn’t just move horizontally• Upwelling is the vertical movement of water

from the bottom upward• These waters are rich in nutrients and help

support marine life• Happens mostly on western coasts of

continents