Earth’s Oceans – “The Water Planet” - Loudoun County Public Schools

[Pages:55]Earth's Oceans ? "The Water Planet"

Unit 6 Chapters 22 - 24

Why does the Earth look mostly blue when viewed from space?

Oceanography

? Oceanography ? is the study of the ocean using chemistry, biology, physics, geology, and other sciences.

Water Molecule

? Water molecule (H20) = 1 Oxygen, 2 Hydrogens

? Polarity ? uneven distribution of charge between H & O

? Hydrogen is positive charge and Oxygen is negative charge = Dipolar molecule

? H bonding - strong bond between a positively charged H atom of one molecule with a negatively charged atom of another molecule.

? Hydrogen bonds determine the structure of water in solid form.

? Arrange in "frame" with large spaces between molecules (less dense, like ice)

+ H H+ O _

+ H H+ O _

Properties of Water

? Oceans cover >70% of Earth's surface

? Density ?

? Salinity and Temperature affect density of seawater

? Ice (solid form of water) is less dense than the liquid form because of the structure

? Ice floats on water.

? Salt concentration ? the more salt the more dense the water is.

? (Dead Sea ? people float on water because salt water is more dense).

Beer_Sheva/Dead_Sea/photo1019336.htm

Seawater

? Salinity ? measure of dissolved salts in water.

? Measure by evaporating water and weighing amount of salt left over.

? Average salinity = 35 practical salinity units (psu) or 35%.

? Based on amount of fresh water entering sea. (so salinity may be different at times ? also depends on climate)

? Seawater liquid between -2?C to 100.3?C (normally water is a liquid between 0?C - 100?C

? Throw salt on sidewalk/road to melt ice. (seawater more stable than pure water)

Freshwater freezes, leaves salt behind in seawater.



Salinity in Seawater can change

? Depends on amount of freshwater coming into sea ? So area with lots of freshwater coming into sea may be less than the average 35% salinity (because less salt, more freshwater)

? Depends on climate ? So area with hot, dry climates will evaporate water more quickly, so salinity is more than average (less freshwater, leaves more salt) ? Area very cold forming ice, salt is left behind in water and freshwater freezes, so salinity would be higher here.

Composition of Seawater

? More than 70 elements make up seawater

? Chloride ~55%

? Sodium ~30.6%

? Sulfate ~7.7%

? Magnesium ~3.7%

? All others ~3%

? Important elements in seawater:

? Salt (Sodium Chloride= NaCl) and magnesium mined from seawater.

? Calcium for hard shells (shellfish)

? Nitrogen and phosphorous from photosynthesis.

Piles of salt, Bolivia

Luca_Galuzzi_2006_a.jpg

?Salts enter ocean via: - Underwater volcanoes - Erode from mineral-

rich rocks - Decomposed marine

organisms.

Temperature Profile of Ocean

? 3 temperature zones:

? Surface zone/Mixed Layer (warmed by sunlight)

? Middle zone/ Thermocline (penetrated by little light, temperatures change rapidly)

? Deep zone (very cold, without light)



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