Chapter 15 Notes
Originated from: Comets and Volcanism
-Impacts of Comets released water
Influences weather and climate
Sonar-map ocean floor
Topex/Poseidon-monitors Ocean’s surface temperature, currents and wave condition
Side-Scan Sonar-new-ocean seafloor scanned in angles
Distrubution-97% oceans-81% in southern hemisphere
-sea level: levels of oceans surface rise and fall due to melting ice.
-1 mm to 2mm per year in response
-71 % of surface covered by oceans-average depth is 3800 m
-Major Oceans- Pacific- ½ of Earth’s Seawaater, Sea Ice-Arctic & Antarctic
Seas-smaller than oceans-landlocked
I. Composition of Ocean Water
B. Gases & Nutrients
N2, O2 & CO2 (dissolves most easily)
Nitrates, phosphates and silicates
Temperature affects amount of gases dissolved.- table 15-1 pg. 392
C. Salinity of Ocean- amount of dissolved solids present (form of ions)
NaCl, (sodium chloride) 78% of dissolved solids
Salinity = 35 ppt 3.5 % dissolved salts
Polar Regions-low-due melting
Equatorial regions-precipitation is abundant-salinities are lower
Depth: surface higher salinity; deeper lower
Amount of fresh water entering ocean are-low salinities-where rivers empty into oceans
D. Physical Properties of Seawater
1- Light-Color- absorbs or reflects sunlight
Penetrates upper 100 m of seawater
Know figure 15-14 page 396
Blue wavelengths reflected- last to be absorbed
2- Ocean Layering-
Temperature: Average Temp 15° C, Freezing Point -2°C to 30ºC- Greater effect on density of water.
Surface water- mixing, relatively constant increasing latitude polar surface waters are much cooler.
Thermocline- zone of rapid temperature change. Occurs not far below the surface. Transitional Layer
Surface water cannot mix with easily with colder deeper water (bottom of ocean).
E. Density of Ocean Water
1.0 g/cm3 pure water
Salinity (salts) and temperature of water- add mass to water
Ocean water between 1.026 and 1.028 g/cm3
II. Ocean Waves-
A. Properties
Wavelength-determines depth at which wave disturbs the water
Wave Base-depth which wave is disturbed-equal to ½ wavelength
Wave height-wind speed, wind duration and fetch
Breakers- friction on bottom of wave – top keeps going
III. Tides- changes in level of the ocean surface-periodic rise and fall of sea level (pull of moon)
IV. Currents- moves on or near surface of the ocean and are driven by winds
Density-caused by salinity and temperature, move slowly in deep ocean systems-Antarctic Bottom Water.
Surface Currents-driven by wind systems
Gyres-closed current systems-landmasses deflect currents-know figure 15-23
Equatorial currents- warm, Atlantic, Pacific and Indian, westward direction
Gulf Stream- moves from Gulf of Mexico- becomes North Atlantic Drift (south of Greenland)
North Atlantic- deep cold current flows, opposite of surface currents
Chapter 16
I. Shoreline Features:
- shaped by waves, tides and currents
- Wave refraction-differences in wave speed causes bending of wave crests: irregular coasts- bend towards headlands-severe erosion
- Rocky Headlands- steep wave-cut cliffs, wave-cut platform-formation of sea stacks and sea arches-undergo severe
erosion
- Beaches-composed of loose sediments deposited and moved about by waves
- Composition-depends on source of material: ex. Hawaiian-Black Sand-volcanic rocks Southern Florida-white and pink
- Estuaries-Figure 16-4 page 415
-lower end of river enter ocean
>-mixture of freshwater and salt
>- Longshore Currents-Figure 16-5 page 416
-flows parallel to shore
-moves large amounts of sediments
-transport in direction of current<
-Rip Currents-flow through gaps in longshore
-Depositional Features-
-seashores constant state of change
-spits and barrier-sediments moved and deposited by longshore currents.
-Spit-narrow bank of sand projects out from coastline
-Barrier Islands-Gulf Coast and Eastern Coast South of New England- unstable and temporary.
-Protective Structures-Groins, jetties and breakwaters interfere with natural shorelines process can cause negative effects.
Ocean Floor-
Two major areas: Continental Margins and Deep Ocean Basin
A. Continental Margins: shallower portions of the ocean floor made up of continental crust
1- Continental Shelf- zone of shallow water, edge of continent. Affected by changes in sea level, erosion or deposition.
2- Continental Slope- Boundary between the continental crust and the oceanic crust
a. submarine canyons
b. continental rise
B. Deep Ocean Basin- include broad, flat plains, submerged volcanic mountains, gigantic volcanic mountain ranges and deep trenches
1- Trenches- long and narrow, deepest features on earth’s surface
Associated with earthquakes, volcanic mountain ranges
And volcanic island arcs
2- Abyssal Plain- cover ½ deep-ocean basin
Flattest regions on earth, thick layers of sediments
Atlantic Ocean
3- Mid-Ocean Ridges-
4- Seamounts- isolated volcanic mountains
Can form islands such as Hawaii-Guyots