Chapter 9: The Hydrosphere

• Liquid at ordinary Earth temperatures

• High heat capacity• Expands when cools• Capillarity• Universal solvent• Water is not distributed evenly

around Earth• Hydrologic cycle

– Ceaseless interchange of moisture in both geographical location & physical state

The Hydrologic Cycle

The Hydrologic Cycle

• 99% stored in oceans, lakes, rivers, glacial ice, or rocks beneath the surface

• Remaining fraction involved in a continuous sequence of movement and change

• Movement is the hydrologic cycle

Figure 9-1

The Hydrologic Cycle

Figure 9-2

• 3 primary movement types – Surface to air

• Evaporation– Air to surface

• Precipitation– Movement

beneath the surface

• Runoff

• Residence times– Minutes to

millennia

The Hydrologic Cycle

Figure 9-3

• Precipitation & evaporation/transpiration balance over time– Evaporation exceeds

precipitation over ocean– Precipitation exceeds

evaporation over land

The Oceans

• Majority of surface is ocean• 4 principal

parts– Pacific– Atlantic– Indian– Arctic– 5th ocean

• Southern Ocean

• Smaller bodies– Seas, gulfs, bays, etc.

Figure 9-5

The Oceans

• Ocean water characteristics– Chemical composition

• Salinity– Sodium & chlorine

– Temperature• Decreases with increasing latitude

– Density• High temperature = low density• High salinity = high density

– Increasing acidity• CO2 absorbed by ocean water =

carbonic acid• Affects microscopic creatures’ shells

Figure 9-6

Movement of Ocean Waters

• 3 primary groups: tides, currents, and waves• Tides

– Bulges in sea surface– Significant in shallow water areas for horizontal placement of water

• Causes of tides– Gravitational attraction of Moon (lunar tides) & Sun (solar tides)– More gravitational force on

side of Earth facing Moon– More centripetal force on

opposite side to keep Earth in orbit

– 2 bulges form on opposite sides of planet

Figure 9-7a

Movement of Ocean Waters

• Causes of tides (cont.)– Two tidal cycles in 25 hours– Flood tide & high tide– Ebb tide & low tide

• Monthly tidal cycles– Tidal range—difference between

high & low tides– Spring tides– Neap tides

• Tidal bore• Global

range of tides

Figure 9-7b and c

Figure 9-9

Movement of Ocean Waters

• Currents– Surface currents

develop from surface wind patterns

– Deep ocean circulations

• Result from differences in temperature & salinity in deep ocean water

• Thermohaline circulation

– Global conveyer-belt circulation

Figure 9-10

Movement of Ocean Waters

• Waves– Disturbances to the sea

surface• Changes shape of the ocean

surface– Disturbances in Earth’s

crust also trigger motion• Tsunami

– Little forward progress is observed

– Wave breaking can result in shifting of water

Permanent Ice – The Cryosphere

• Cryosphere– 2nd largest water storage on

Earth– 2 groups

• Ice on land – Alpine glaciers– Continental ice sheets

• Ice in water– Ice pack– Ice shelf– Ice floe– Iceberg

– About 10% of Earth’s surface is ice Figure 9-12

Permanent Ice – Glaciers• Natural accumulation of land ice that flows

downslope or out from center of accumulation

Figures 19-5a & 19-17

Permanent Ice – Pack Ice

• Largest ice pack found in Arctic ocean

Figure 9-13

16

Permanent Ice – Ice Shelf

• Several large ice shelves attached to Antarctica– Larsen-B Ice Shelf

– Broke off 2002– Larsen-C & Wilkins Ice Shelves

are currently disintegrating

17

Permanent Ice – Ice Floe & Iceberg

Permanent Ice –

Permafrost• Permafrost

– Permanently frozen ground

Figures 9-15 & 9-16

Surface Waters

• 0.02% of water supply• Lakes—bodies of water

surrounded by land– Need:

• Natural basin• Sufficient water supply

– Most are short-lived• Human alteration of lakes

– Irrigation– Water diversion projects– Reservoirs

• Hydroelectric power• Municipal water• Agriculture

Figures 9-17 & 9-19

• Lakes are more common in areas that have been glaciated

Surface Waters

Figure 19-28

Surface Waters

• Swamps and Marshes– Flattish places periodically

submerged, but shallow enough to permit plant growth

– Swamps = trees

– Marshes =grasses

Figure 9-23

Surface Waters

• Streams– Allow for drainage of land

surface water towards oceans

– Drainage basins

Figure 9-24

Underground Water

• Water beneath land surface worldwide– Underground water vs. Groundwater

• Precipitation or water basins provide water sources

• Quantity held depends on:– Porosity– Permeability

Underground Water

• Aquifers– Where groundwater is stored– Confined vs. unconfined

• Aquicludes– Impermeable

rock layer that prevents water movement

Figure 9-25

Underground Water

• Zone of aeration– Topmost layer– Mix of air & water in pore

spaces– Water amount fluctuates

rapidly • Zone of saturation

– ALL pore spaces filled with water

– Groundwater– Top of zone = water table– Well water drawn faster than

replenished creates a cone of depression

Figure 9-26

Underground Water

• Zone of confined water– Water is trapped between 2 aquicludes– Pressure causes water to rise to piezometric surface– Artesian well vs. sub-artesian

• Waterless zone– Pressure too

great to sustain water

Figure 9-27

Underground Water

• Groundwater mining– Slow accumulation vs.

rapid human use– Ogallala Aquifer

• Water table drops with increased use

• Numerous wells tapped• Unsustainable situation

Figure 9-30

Summary

• Most of the water on the planet exists in the oceans• The hydrologic cycle describes the transition of water from land to sea to air• Ocean water has numerous defining characteristics• Ocean water movement is affected by gravitational pull from celestial objects (tides)• Ocean water moves through currents based on salinity and temperature• Winds and ocean surface disturbances result in waves on the ocean surface• The cryosphere holds a large percentage of the Earth’s water content• The ice in the cryosphere contains no salt• Permafrost is permanently frozen landscape• Surface water represents a very small fraction of the total Earth water content• Surface water processes constitute an important part of the hydrologic cycle• Lakes are bodies of water surrounded by land• Swamps and marshes exist in areas that are shallow and can support plant life• Rivers and streams help distribute water back to the oceans and replenish lakes• Underground water exists due to water basin seeping or precipitation• Human interactions in above ground and below ground water areas have drastically

altered the hydrosphere