Outline 12 Earth\'s Water PDF

Preview

Summary

STEPHANIE WELCH...

Description

ESSC 101 Lecture Outline 12 – Earth’s Water and Oceans 

Distribution of Earth’s Water: Earth has stable, liquid water on the planet with makes life possible. 70% of earth’s surface is covered in water. 2% of water is trapped in form of ice at poles



The Hydrologic Cycle (Fig. 10.1): the movement and interchange of water between the sea, air, and land Starts and ends with water in the oceans. Heat from the sun that allows for the cycle.

o evaporation – taking a liquid and turning it into a gas. Solar radiation provides energy, air becomes saturated with water. Water vapor is absolute humidity (0-4%). It is more lightweight and less dense. As you move away

o

o

o

o

from sea level, temperature decreases. Water vapor reaches an altitude where temps are too cold to keep the water in a gaseous state. condensation – water vapor cools, condenses and forms clouds. A cloud is pieces of particles suspended into the atmosphere with a drop of water condensed onto the particles. Clouds at earth’s surface is fog; humid air moves over a cold, ground surface. Clouds continue to get dense and heavy that they can fall through the atmosphere unto the surface as precipitation. precipitation – rain or snow on the continents. Once it hits earth it either pulls up on the surface and runoff along the surface or it soaks up the water becoming groundwater. It continues to move runoff – water flowing over land surface, always returning to a base level (usually sea-level), forming rivers. At the mouth of rivers forms sediment buildup infiltration – water soaking into the ground, usually moving toward sealevel (groundwater). 75% of earth’s surface is covered with sediment/sedimentary rocks. Water filters through soil until it gets to a porous boundary letting the water flow through. The water ultimately moves back to sea level.



Dihydrogen Monoxide – Water o Universal solvent because of the structure of the molecule is polar (positive and negative end) o Solvent is something you dissolve things into o Dissolves things with an ionic bond  Water detaches the ions and replaces the need for the ions to be bonded together  Reasons why oceans are salty



Salinity o Total amount of dissolved solute in water (saltiness); g/L or parts per thousand o Freshwater (rivers, lakes, shallow groundwater) < 1g/L

o Brackish water (estuaries) 1-30g/L o Saltwater (oceans) 30-50g/L o Brine (deep groundwater) > 50g/L

Chlorine doesn’t form bonds easily. To get it out of seawater, there has to be an increase in the concrentration of chlorine and sodium to precipitate out salts. Sodium gets in through the dissolution of silicate minerals. These minerals can be pumped into the ocean but some are easier to precipitate out.

Temperatures are higher near the equator; more dissolution less precipitation of minerals higher salinity in warmer water. Higher salinity in deep, central parts of the ocean. Oceans have become more salty over time and will continue to do so. o Source(s) of Salinity in Oceans  Water cycle: dissolution of minerals into groundwater and surface water







Hydrothermal process in mid ocean ridges: dissolution of minerals into hot water at mid ocean ridges. Tectonic plates move apart creating new rock. Water is pulled into the crust and pumped back into ocean. Amount of hot water pumped back into seas allowed for life to start billions of years ago

Oceans of the World o Pacific Ocean: largest, most ancient, and deepest ocean. Mariana Trench is the deepest point at 35,000 feet; plates are subducting back into the mantle o Atlantic Ocean: about half the size of the Pacific Ocean but is growing larger. Longest mid-ocean ridge on earth; mid-Atlantic ridge. Started to form as Pangea broke apart. o Indian Ocean: slightly smaller than the Atlantic but about as deep. India slams into Asia and continues to move upward; convergent. Indian ocean slides under islands which caused 2004 tsunami. o Arctic Ocean: polar. ¼ of the depth of the rest of the oceans. Covered by permanent layer of ice. Lots of sea ice and continental glaciers makes the arctic ocean become a part of pacific and Atlantic oceans. During ice ages, sea level is relatively low o Southern Ocean: polar. Also called the Antarctic ocean. Defined by the meeting of ocean currents near Antarctica. Cold water currents keep temps lower at north pole vs south pole. Ocean Currents:

o Coldwater current allows for water of differ temps to move across earth’s surface. Very important for stability of life and maintenance of earth’s ocean temps. o Surface currents distribute water around the globe and are primarily driven by the Coriolis Force which occurs due to the Earth’s rotation and deflects moving water and air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Moves from equator which is warm to poles which are colder. o Warm and cold water currents form as a result of the gyres that mimic the Coriolis deflection  Water moving across the surface of earth as earth is rotating from under it  Gyres mimic the Coriolis deflection in each hemisphere  Hurricanes are so abundant in the North Atlantic and Gulf of Mexico because the Gulf Stream and Northern Equatorial Currents are very warm o Variations in temperature and salinity cause water to circulate at depth because density increases as temperature decreases, and increasing salinity also causes seawater density to increase  Warm water rises to the surface, cold water sinks down...