The Structure of Hydrosphere Muhammad Fahad Ansari 12IEEM14
The Structure of Hydrosphere• Oceans—96.5% of • Fresh water water found here distribution: – Ice: 1.762%• Fresh water—3.5% of – Groundwater: 1.7% water found here – Surface Fresh Water: 0.014% – Atmosphere and soil: 0.002%
Understanding Where Your Water Is Located—Oceans and Ice• What bodies of water hold the largest amount of water? – Oceans—the largest bodies of water on Earth (contain salt water only)• What features house water as ice? – Icebergs: a large piece of freshwater ice floating in open waters – Glaciers: any large mass of ice that moves slowly over land – *permanent snow areas also “house” water as ice
Fresh Water Locations—Surface Water• What is the difference between a watershed and a river basin? – Both terms describe land that drains into a river, stream or lake • River Basin: the term used to describe an area that drains into a large river • Watershed: the term used to describe an area that drains into a smaller river or stream
Fresh Water Locations—River Basins and Watersheds• Larger river basins are made up of many interconnected watersheds – Example: Cape Fear and Neuse River Basins are made of many small watersheds• The water in a watershed runs to the lowest point—a river, stream, lake, or ocean
Fresh Water Locations—Rivers, Streams, and Lakes• What is a river? – A large channel along which water is continually flowing down a slope—made of many streams that come together• What is a stream? – A small channel along which water is continually flowing down a slope—made of small gullies• What is a lake? – A body of water of considerable size contained on a body of land
Fresh Water Locations--Groundwater• What is groundwater? – The water found in cracks and pores in sand, gravel and rocks below the earth’s surface• What is an aquifer? – A porous rock layer underground that is a reservoir for water
Other Surface Waters• What is a wetland? – An area where the water table is at, near or above the land surface long enough during the year to support adapted plant growth• What are the types of wetlands? – Swamps, bogs, and marshes • Swamp: a wetland dominated by trees • Bogs: a wetland dominated by peat moss • Marshes: a wetland dominated by grasses
THE EARTH’S HYDROSPHERE• The Earth’s liquid water constitutes the hydrosphere.• The vast majority of Earth’s water is in the oceans (salt water), with smaller, but geologically important, quantities of fresh water in lakes, rivers, and ground water.• The components of the hydrosphere, as well as the cryosphere (frozen water), the atmosphere, and the biosphere, participate in the global hydrologic cycle.• Earth’s water supply has had, since Earth was created, major influences on Earth’s climate, its landscape and mineralogy, the composition of its atmosphere, and on the origin and evolution of life. – The total mass of Earth’s water is about 300 times the mass of the atmosphere. – Without water, which facilitates the formation of carbonate rock, the atmospheric content of CO2 would be far higher than it is.
THE EARTH’S HYDROSPHERE: Distribution of Water on Earth Volume Percent of TotalOCEANS 1,350 x 1015 m3 97.3CRYOSPHERE 29 x 1015 m3 2.1(Glaciers & Polar Ice)UNDERGROUND 8.4 x 1015 m3 0.6(Aquifers)LAKES & RIVERS 0.2 x 1015 m3 0.01ATMOSPHERE 0.013 x 1015 m3 0.001BIOSPHERE 0.0006 x 1015 m3 4 x 10-5
THE EARTH’S HYDROSPHERE• The hydrosphere, along with the atmosphere and cryosphere, are primarily responsible for weathering and erosion of land surfaces.• Rain water, in combination with atmospheric CO2, is primarily responsible for chemical weathering by carbonic acid, H2CO3.• The amount of CO2 dissolved in the oceans is much larger than that currently in the atmosphere. Since the solubility of CO2 in water decreases with temperature, global warming could produce a positive feedback effect by releasing oceanic CO2.• Man-made and volcanic pollution can increase weathering by providing much stronger acids (“acid rain”; e.g. H2SO4), and by increasing atmospheric CO2.• Rain, plus the river and stream components of the hydrosphere, also provide mechanical erosion of rocks and convert them to soils and sediments.
LIFE IN THE OCEANS• Throughout Earth’s history, the oceans have had major influences on the evolution and propagation of life, and vice versa.• Early in Earth’s history, before the advent of photosynthesis on a large scale, there was no atmospheric ozone layer to protect life forms on the surface from damaging solar ultraviolet radiation.• Therefore, the oceans (and other large bodies of water) provided the only UV-protected (but visible light illuminated) habitats for the original procaryotic life forms, as well as essential nutrients.• Life forms have also had significant influences on the oceans and ocean beds, because of their capabilities to convert carbon dioxide and soluble calcium compounds into limestone (calcium carbonate, CaCO3).
THE EARTH’S CRYOSPHERE• Earth’s supply of frozen water, the cryosphere, is second only to the oceans in water content.• The cryosphere consists mainly of the permanent ice caps of Antarctica and Greenland, with much smaller amounts in Arctic and mountain glaciers.• Major changes in sea level can occur during times of global climate change (ice ages and global warming), due to associated changes in the water content of the cryosphere.• During ice ages, glaciers can cover major parts of Earth’s land area year-round for hundreds or thousands of years.• The advance and retreat of glaciers can also produce major erosion and re-configuration of the landscape.• Ice ages and global warming can have major effects on the biosphere as well.
Permafrost in Land Areas• Land areas in polar regions, such as Antarctica and Greenland, and the north slopes of Alaska and Siberia, have zones below their surfaces in which ground water remains frozen year-round.• Regions in which soil water is permanently frozen constitute what is known as permafrost.
ICE AGES AND GLOBAL WARMING• The most recent “ice age” ended about 12,000 years ago, which was prior to the advent of civilized human history.• It is still unknown as to what causes the advent of ice ages, and the extent that they occur in cycles independent of human activities.• At the current time, we are experiencing a slow global warming, but it is not known to what extent this is part of a natural cycle as distinct from human-induced (by increasing the amount of carbon dioxide and other “greenhouse gases”, due to combustion of fossil fuels and other human activities).• There is concern that the increasing use of fossil fuels might induce a “runaway greenhouse” effect, because heating of the atmosphere could, by heating of the oceans and other water bodies, result in increasing water vapor in the atmosphere (which is also a “greenhouse gas”)!• Global warming would also result in melting of the polar ice caps, which would raise the water level of the oceans and cause flooding of coastal areas of the continents.