•Earth’s Waters

• This is one of the water canals of the present-day system in Phoenix, Arizona. These canals were reconstructed from a system that was built by American Indians, then abandoned. Phoenix is named after a mythical bird that was consumed by fire and then arose from its ashes.

• Water on the Earth

• The distribution of all the water found on the earth's surface.

• On the average, more water is evaporated from the ocean than is returned by precipitation. More water is precipitated over the land than evaporates. The difference is returned to the ocean by rivers and streams.

• Freshwater– The source of freshwater is mostly from precipitation– Most precipitation returns to the atmosphere through

evaporation– The remaining either

• Becomes runoff

• Soaks into the ground to become groundwater

– If the runoff collects into sheets in a small body of moving water it is a stream

– Amount of rainfall that becomes runoff or groundwater depends on:• Type of soil• Soil moisture content• Vegetation• Slope of land• Intensity of rainfall

• Surface Water– The land that is drained by a stream is called a watershed.– Smaller watersheds run into larger rivers to form their

watersheds.

• The approximate watersheds of the Columbia River, the Colorado River, and the Mississippi River.

– Adjacent watersheds are separated by a divide.• Rainfall on one side if the divide runs into one

watershed and rainfall on the other side of the divide runs into the adjacent watershed.

• The Continental Divide (Great Divide)separates watersheds that drain into opposite sides of the continent

– A small body of standing water is called a pond– A larger body of standing water is called a lake.– A standing body of water is called a reservoir if it is

used for:• Water storage• Flood control• The generation of electricity

• Groundwater– Water from a saturated zone created from the percolation

of rainwater is called groundwater.• Water percolates down to the groundwater through

pores in the soil and rock above it.• The pore size determines how well the water can

percolate and is a measure of the porosity of the sediment or rock layer.

• The ability of the ground to transmit water to the groundwater is a measure of the permeability of the ground.

• Some of the precipitation soaks into the ground to become groundwater. Groundwater slowly moves underground, and some of it emerges in streambeds keeping the streams running during dry spells.

• (A)Sand and gravel have large, irregular particles with large pore spaces, so they have a high porosity. Water can move from one pore space to the next, so they also have a high permeability. (B) Clay has small, flat particles, so it has a low porosity and is practically impermeable because water cannot move from one pore to the next.

– Groundwater will continue to percolate through a permeable soil until it reaches a zone of saturation known as the water table.

– An aquifer is a highly permeable soil that is capable of producing water

– Groundwater that is under pressure because it is under an impermeable layer is called an artesian aquifer.

• Groundwater from below the water table seeps into lakes, streams, and swamps and returns to the surface naturally at a spring. Groundwater eventually returns to the ocean, but the trip may take hundreds of years.

• An artesian aquifer has groundwater that is under pressure from the water at higher elevations. The pressure will cause the water to rise above the water table in a well drilled into the aquifer, becoming a flowing well if the pressure is sufficiently high.

• Freshwater as a Resource– Most water use is for agriculture, for the production of

electricity, or for industrial purposes.– This use depends on:

• Relative proportions of industry, agriculture, and the population

• Climate

• Nature of industry or agriculture

– Most water is obtained for use from surface water.• This water must be highly processed as it contains a great

number of contaminants due to its exposure to the environment

• The filtering beds of a city water treatment facility. Surface water contains more sediments, bacteria, and other suspended materials because it is active on the surface and is exposed to the atmosphere. This means that surface water must be filtered and treated when used as a domestic resource. Such processing is not required when groundwater is used as the resource.

• This is groundwater pumped from the ground for irrigation. In some areas, groundwater is being removed from the ground like this faster than it is being replaced by precipitation, resulting in a water table that is falling deeper and deeper. It is thus possible that the groundwater resource will soon become depleted in some areas.

• Seawater

• A modern-day tuna fishing boat. Note the time-tested "crows nest" lookout on the mast and the more modern helicopter fastened on top. Both are used to look for schools of tuna, but the helicopter also does other jobs.

• Oceans and Seas– 70 % of the Earth’s water is located in oceans.

• This water is high in salt concentration and is not fit for use in human consumption.

– Three regions of the Earth’s Oceans are:• Atlantic Ocean• Indian Ocean• Pacific Ocean

• Distribution of the ocean and major seas on the earth's surface. There is really only one ocean; for example, where is the boundary between the Pacific, Atlantic, and Indian oceans in the Southern Hemisphere?

– An ocean is a continuous body of water on the Earth’s surface

– A sea is a smaller part of the ocean designated by specific location characteristics that delineate it from other parts of large bodies of water.

• The Nature of Seawater– Seawater continuously cycles through the hydrologic

cycle.– Dissolved solids are also constantly being added to the

ocean basin.• Plate techtonics can then recycle these sediments back

into the Earth’s interior.• Dissolved materials are also returned by other natural

processes.

– The salinity of the ocean is approximately 3.5 % by mass– Sea water does not freeze as lakes do because as the

water approaches the freezing point the salts become more concentrated, lowering the freezing temperature.

– Since the oceans waters move continuously, the materials are mixed very well.

• Salinity is defined as the mass of salts dissolved in 1.0 kg of seawater. Thus, if a sample of seawater has a salinity of 35 0/00, a 1,000 g sample would evaporate 965 g of water and leave 35 g of sea salts behind.

• Air will dissolve in water, and cooler water will dissolve more air than warmer water. The bubbles you see here are bubbles of carbon dioxide that came out of solution as the soda became warmer.

• Movement of Seawater– Introduction

• Seawater is in constant motion due to waves and currents

– Waves• This is a disturbance that travels across the surface of

the water.• Each wave has a high point or a crest, followed by a

low point, or trough

• The surface of the ocean is rarely, if ever, still. Any disturbance can produce a wave, but most waves on the open ocean are formed by a local wind.

• Waves are measured by:– Wave height – vertical distance from the top of one

wave crest to the bottom of the next wave trough.– Wavelength – horizontal distance between crests– Wave period – time required for 2 crests to arrive at a

given point.• When the wave front breaks due to its height it is called a

breaker.• The zone where the breaker occurs is called the surf.• Undertow

– Where the water that accumulates on the shore returns to the ocean by moving underneath of the breakers.

• The simplest form of ocean waves, showing some basic characteristics. Most waves do not look like this representation because most are complicated mixtures of superimposed waves with a wide range of sizes and speeds.

• Water particles are moved in a circular motion by a wave passing in the open ocean. On the surface, a water particle traces out a circle with a diameter that is equal to the wave height. The diameters of the circles traced out by water particles decrease with depth to a depth that is equal to one-half the wavelength of the ocean wave.

• As a pattern of swell approaches a gently sloping beach, friction between the circular motion of the water particles and the bottom slows the wave, and the wave front becomes steeper and steeper. When the depth is about one and one-third times the wave height, the wave breaks forward, moving water toward the beach.

• The white foam is in the surf zone, which is where the waves grow taller and taller, then break forward into a froth of turbulence.

• Longshore current– When the accumulated water is pushed along the

shore by the waves.• Rip current

– A strong stream of water that returns water to the ocean by bursts against the waves.

• Tsunamis– Huge destructive waves produced by movement of

the Earth’s crust of by underwater landslides

• Breakers result in a buildup of water along the beach that moves as a longshore current. Where it finds a shore bottom that allows it to return to the sea, it surges out in a strong flow called a rip current.

– Ocean Currents• Introduction

– Streams of water that move in a set path.• Density currents

– factors influencing the density of seawater» Temperature» salinity» suspended materials

– When there is a difference in density of seawater due to these three factors there is a movement of water, just as air moves due to density differences

– Cold water sinks and warm water rises» Cold water will sink at the poles and move

under warm water to the equator where it will be warmed and return to the surface

• A cold-density current carries about 250 times more water than the Mississippi River from the Arctic and between Greenland and Iceland to the deep Atlantic Ocean. At about 30ON latitude, it meets water that has moved by cold-density currents all the way from the Antarctic.

• Surface currents– The winds at the surface of the ocean drive the

surface currents.» A gyre is a system of moving water at the mid

latitudes» These gyres rotate to the left in the Northern

Hemisphere and to the right in the Southern Hemisphere due to the Coriolis Effect.

• The earth's system of ocean currents.

• The Ocean Floor

• Continental Shelf– A zone of shallow water at the edges of the continents– Created by erosion of exposed soil due to water being

locked up in glaciers.

• Continental Slope– A steep area just off the continental shelf that steeply

slopes away from the shelf– Occurs between the continental shelf and the deep ocean

basins.

• Submarine Canyons– Gullies cut in the continental slope

• Ocean Basins– The very bottom of the ocean floor.– The deepest part of the ocean

• Abyssal Plain.– The relatively flat portion of the ocean basin

• Ridges.– Mountain chains that rise up from the abyssal plain

several thousand meters.

• Trenches– A long narrow trough along the edges of the ocean basin.

• Seamounts– Steep volcanic peaks in the ocean basin.– Rise more that 1 km above the ocean floor– The Hawaiian Islands are Seamounts that extend above

the surface of the ocean.

• Some features of the ocean floor. Note that the inclination of the features is not as steep as this vertical exaggeration would suggest.

• The location of some of the larger ridges and trenches of the earth's ocean floor.