Chapter 7 Outline

Chapter 7 Outline - Chapter 7: Water and Atmospheric...

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Chapter 7: Water and Atmospheric Moisture Introduction Pure water color-/odor-/tasteless; b/c solvent, rarely occurs in nature; H 2 O weighs 1 g/cm 3 /1 kg/L; is ~70% of our bodies by weight; major ingredient in plants, animals, food Water on Earth Earth’s hydrosphere has ~1.36 bil km 3 water; much earth’s H 2 O fr icy comets, H-/O 2 -laden debris fr forming of planet; outgassing - cont’g process by which water, water vapor emerge to surface fr lyrs w/in/below crust, 25+ km below earth; early atmos, huge qtys outgassed water vapor condensed: Rained to Earth; for it to stay on Earth’s surface, land temps had to drop < boiling pt 100°C- occurred 3.8 bil yrs ago; lowest places on Earth filled w/water- ponds oceans; huge flows H 2 O washed over landscape, carrying dissolved, solid materials to early seas/oceans; outgassing visible in volc eruptions, geysers , seepage to surface Worldwide Equilibrium H 2 O most common cmpnd on Earth; qty ~constant tho H 2 O cont’sly lost fr sys- when dissociates into H + O 2 & H escapes to space/when brks down, forms new cmpds w/other elements; pristine water not prev’sly at surface emerges fr Earth’s crust, replaces lost water in sys= water qty in steady-state equilb Still, worldwide changes in sea lvl only- eustasy - occur; some changes due to varied amt of water stored in glaciers/ice sheets- glacio-eustatic factors; cooler times= more water in glaciers/ice sheets/ lower sea lvl; warmer= less water stored as ice/sea lvl rises; sea lvl rising worldwide w/higher temps Isostasy - actual phys changes in landmasses tht cause apprnt changes in sea lvl relative to coastal envts Distribution of Earth’s Water Today Ocean, land surfaces distributed unevenly; appears to have oceanic hemisphere (N Hem) & land hem (S Hem); oceans (Pacific, Atlantic, Indian, Arctic) hold 97.22% of all water- 1.321 bil km 3 ; Southern Ocean - extreme S parts of 1 st 3 above; only 2.78% Earth’s water freshwater (non-saline/non-oceanic) Ice sheets, glaciers hold most- 77.14%- Earth freshwater; + subsurface groundwater, frozen surface water = 99.36% freshwater; rest in lakes, rivers, streams; lgst vol lakewater in Russia’s Lake Baykal; 70% of lakewater in N America, Africa, Asia; not connected to ocean- saline lakes, salty inland seas: Usu exist in regs of interior river drainage (no outlet to ocean) tht lets salts become concentrated; eg Utah’s Great Salt Lake; water molc traveling thru atmos/surface-water paths moves thru whole hydrologic cyc (ocean-atmos-precipitation-runoff) in < 2 wks; water molc in deep-ocean circ/glacier/ groundwater takes 1000s yrs to migrate thru sys Unique Properties of Water Earth’s distance fr Sun puts it in good temperate zone- allows all 3 states of water to occur naturally on Earth; water has uncommon properties- 2H + 1O 2 => H 2 O molc w/covalent bond tht stays stable in Earth’s envt; b/c H side positive charge/O side neg=> polarity - water molcs attract each other in:
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Chapter 7 Outline - Chapter 7: Water and Atmospheric...

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