Unit 1 Marine Geology, Chemistry, Physics PDF

UNIT 1: MARINE GEOLOGY, CHEMISTRY, PHYSICS Structure of the Earth Oceans cover about 71% of the earth's surface Northern Hemisphere is 61% ocean Southern Hemisphere is 80% ocean Ocean basins: ("World Ocean") Pacific Ocean - largest and deepest Atlantic Ocean - roughly equal Indian...

UNIT 1: MARINE GEOLOGY, CHEMISTRY, PHYSICS Structure of the Earth Oceans cover about 71% of the earth's surface Northern Hemisphere is 61% ocean Southern Hemisphere is 80% ocean Ocean basins: ("World Ocean") Pacific Ocean - largest and deepest Atlantic Ocean - roughly equal Indian Ocean - roughly equal Arctic Ocean - smallest and shallowest Density decreases from the center out Oceanic Crust Continental Crust 3.0 g/cm3 2.7 g/cm3 *think of the crust (both oceanic young old and continental) as chunks of ice dark light floating on water (mantle) basalt (Fe, Mg) granite (Na, K, quartz) All life on the earth is at the "mercy of the mantle"...it moves and we move!! Plate Tectonics Sir Francis Bacon: suggested that the continents were one big supercontinent (fit together like puzzle pieces) Alfred Wegener: proposed the hypothesis of continental drift in 1912 Pangea: single supercontinent that existed 180 million years ago Wegener's Questions: Were South America and Africa ever connected? What force was powerful enough to pull them apart? Evidence for Continental Drift: continental margin configuration - 75% match rocks and fossils match across the Atlantic rock magnetism ocean bedrock age (nothing older than 175 million years; oldest land rock 3.9 billion years) platetectonicsfuture Plate Boundaries - motion on one plate generates motion on another divergent two plates move in opposite directions creates new oceanic crust results in mid ocean ridges also known as seafloor spreading example: Mid Atlantic Ridge convergent subduction two plates (oceanic and oceanic) collide and create a trench and island arc example: Mariana's Trench,Japan two plates (oceanic and continental) collide and create a trench and volcanic mountain range example: Andes compression two plates (continental and continental) collide and create mountain range example: Himalayas lateral (transform) two plates moved past each other in opposite directions create faults example: San Andreas Fault tsunami tsunami tsunami Marine Sediments Characteristics of Marine Sediments particle size: indicates origin, mode of transport shape: different shapes carried different distances color: indicates composition white: calcium carbonate black: high organic material, low oxygen, basalt red: iron oxide gray: high silica content Types of Marine Sediments pelagic: derived from processes that occur in the ocean biogenous: composed of skeletons or shells of microscopic organisms inorganic: 70% clay, usually comes from land and carried out to sea by currents volcanic: either ash carried by the wind that sinks or lava flows on the seafloor lithogenous: derived from the physical or chemical breakdown of rocks from land grainofsand whatissonar topographical features Properties of Water can exist in three states liquid (water), gas (vapor), solid (ice) high boiling point 100 degrees Celsius viscosity "thickness" of the water decreased temperature increases the viscosity density mass/volume ice is less dense than water and floats decreased temperature increased density freezing point 0 degrees Celsius ice can be a reflective shield for the earth saltwater does not freeze high heat capacity/high specific heat ability of water to hold heat energy resist rapid changes in temperature this is why coastal areas are more pleasant in both the winter and summer high surface tension forms "skin" on surface of the water enables some organisms to "walk" on water enables phytoplankton to remain at the surface solvent property water can dissolve more substances than any other liquid Seawater Composition salinity: measures the total amount of "salts" dissolved in seawater salts are composed of: sources: chloride sediments sodium runoff sulfate erosion of land magnesium calcium potassium Rule of Constant Proportions: concentration of dissolved salts varies (due to precipitation and evaporation) but the overall percentage does not Percentage: 3.5%, or 35 ppt (every 1 kg has 35 grams) (35/1000 = 0.035 X 100 = 3.5%) blue: below 33, red above 37.4 Red Sea has a high salinity due to high rates of evaporation, low rainfall, low river outflow, and confined circulation Ocean Depth Profiles salinity surface water is usually well mixed by waves, winds and tides below the surface is the halocline (layer where salinity changes rapidly) at some point it stabilizes (rule of constant proportions) temperature below the surface is the thermocline (layer where temperature changes rapidly) density temperature and salinity determine the density water becomes denser (heavier) as it gets saltier, colder or both below the surface is the pycnocline (layer in which density changes rapidly) Analyze Graphs Dissolved Gases oxygen atmosphere is 21% O2 seawater is 0-9% O2 used by aerobic organisms source: photosynthesis areas of high levels of O2 rocky, sandy beaches, high surface winds, waves water turbulence increases levels of O2 below the surface is the oxygen minimum layer layer at which oxygen is close to 0 (anoxic) carbon dioxide essential for photosynthesis sources: cellular respiration, diffusion from the atmosphere, and calcium carbonate of corals nitrogen essential for building amino acids and proteins source: diffusion from the atmosphere organisms are unable to use free N2; it must be converted into nitrates, nitrites, ammonia nitrogen fixation is the process by which free nitrogen is converted into a usable form for organisms by cyanobacteria Transparency seawater is relatively transparent depends upon how much material is suspended or dissolved in the water turbidity measures the cloudiness when turbidity increases, the amount of light decreases; photosynthesis is impacted different color light penetrates to different depths so as depth increases, more colors of the visible spectrum are filtered out Color Absorption red 10 m yellow 20 m green 70 m blue 250m* * this is why the ocean is blue Pressure as depth increases, pressure increases gases become compressed with depth organisms have physical adaptations like gas floats and swim bladders to deal with changes in pressure as they migrate in the water column Water Movement Types of Water Movements waves - initiated by wind at surface tides - affected by moon, sun, earth vertical - upwelling, downwelling currents - large scale Waves ocean waves waves wave size function of wind speed, time wind is in contact with water, wind fetch (area of contact), topography water molecule motion water molecules do not travel with a wave, only the energy wave structure cortesbank beach waves plunging waves moderately steep slope spilling waves gently sloping beaches surging waves vertical cliff wall Tides Function of sun's gravitational pull moon's gravitational pull rotation of the earth gravitational forces: pull water rotation: pushes water Daily Tide Cycle Types of Tides (in 24 hour period): diurnal 1 high, 1 low semi-diurnal 2 high, 2 low, equal height mixed semi-diurnal (California) 2 high, 2 low, unequal heights tides Scott's Bay Monthly Tidal Cycle spring tide - sun, moon, earth, straight line neap tide - sun, moon, earth, right angle 28 day cycle: day 01 - full moon, spring tide day 08 - first quarter moon, neap tide day 15 - new moon, spring tide day 22 - last quarter moon, neap tide Vertical Water Movements sinking cold water also known as overturn upwelling restores nutrients back to the surface waters downwelling moves heat and oxygen to the deep cycle nutrients, increase oxygen, remove waste distribute organisms, distribute gametes upwelling Coriolis Effect - deflection of water Ekman Transport - spiraling of water corioliseffect Currents affected by earth's rotation, topography, winds, density and tides currents