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OCNG 251: EXAM 1
Oceans:
1. Pacific
2. Atlantic
3. Indian
4. Arctic
5. Antarctic or Southern Ocean |
1. Largest, deepest
2. Second largest
3. Mainly southern hemisphere
4. smallest, shallowest, ice covered
5. Connects Pacific, Atlantic, and Indian |
Seas vs. Oceans |
- Smaller and shallower than oceans
- Salt water
- Usually enclosed by land
|
Who determined earth's circumference? |
Eratosthenes in 200 BC |
First world map? |
Ptolemy 150 AD *error in assumption, 29,000 instead of 40,000* |
Marco Polo |
Traveled to Cathy (China) in 1275 |
Ptolemy's new map |
republished map in 1410 wanted riches from "new world" to the east |
Rediscovery of the Americas |
- Chris Columbus reached San Salvador Oct. 1492
- Thought he reached Asia owing to error in estimate of earth's size |
Latitude
Longitude |
- North & South
- East & West
- 15 degrees per hour
- Each degree = 60 mins |
How did they tell time in 1700's? |
Sun Dial
Hour Glass
Pengelium |
Who invented chronometer? (watch) |
John Harrison |
Captain James Cook |
- First accurate maps by using chronometer
- To determine time relative to Greenwich to calc. longitude |
Who devised a chart of Gulf Stream in 1769 |
Ben Franklin & Timothy Folger |
Charles Darwin |
- Voyage of HMS Beagle
- Observed and described the life history of coral reefs
- "The Origin of Species"
- Natural selection |
Challenger Expedition |
first entirely devoted to science spurred by Charles Darwin's work |
Polar Oceanography |
- Fram drifted in the ice for over 3 years (1893-96)
- Drifted across the arctic proved no continent existed in arctic sea |
Oceanography & World Wars |
- Submersible Exploration
- Trieste (french)
- DSRV (found titanic)
- NR-1 (Nuclear powered sub)
- GPS
- Military application
- Transmission of sound
- Ocean-floor bathymetry |
Jacques Cousteau |
Developed scuba gear (not original founder) |
Nature of scientific inquiry |
- Natural phenomena governed by physical process
- Physical process similar today as in the past
- Scientists discover these processes and
- Make predictions |
Scientific method |
Observation
Hypotheses
Testing and modification of hypotheses
Theory |
Universe
Galaxy |
- Huge space which contains all of the matter and energy in existence
- one of billions of systems, each a giant collection of gas, dust and billions of stars |
Formation of Solar System and Earth |
Nebular Hypothesis: Contraction of gas and dust cloud by gravity, contacting from heavy elements that are drawn to the center of clouds through Fusion 4.5 billion years ago |
Internal warming of each planet |
Radioactive decay |
Earth's Internal structure |
- Lithosphere (Rigid)
- Asthenosphere (Plastic)
- Mesosphere (Rigid)
- Outter Core (Liquid)
- Inner Core (Rigid due to pressure) |
Lithosphere |
- covers earths surface
- floats on top of Astenosphere |
Oceanic Crust
Continental Crust
|
Basalt (thicker)
Continental Crust (thiner)
|
Archimedes Principle |
floating body displaces a volume of water equal to its own weight |
Where did the oceans and atmosphere come from? |
Outgassing (4 billion years ago) *No Oxygen* |
Ocean salinity |
Rain dissolves from rocks
Ocean salinity constant over past 4 billion years |
Earliest life forms in Ocean |
3.5 billion years ago |
Types of life organisms: |
Heterotrophs (animals): External food supply
Autotrophs (plants): Manufacture their own food supply (photosynthesis) |
Photosynthesis |
Light + Water + CO2 >> Sugar +O2
- Steep rise in Oxygen 2 billion years ago
- Most anaerobic bacteria died out |
Respiration |
Sugar + O2 >> Water + CO2 + Heat |
Radiometric age dating |
Spontaneous change/decay
half life
* Not everything can be dated b/c not everything has uranium*
|
Evidence for continental drift? |
- Puzzle-like fit of continents
- App mnts match up with Caledonian mtns in Europe
- Sediment deposit and Fossils other continents |
Why reasons for different environment years ago? |
1. Climate distribution was completely different
2. Continents were at different locations (latitude) |
Plate tectonics explains: |
Global distribution of:
Volcanoes
Earthquakes
Faults
Mountain belts
Feature of seafloor
|
Paleomagnetism |
Orientation and intensity of magnetism changes over time |
Magnetic DIP is dependent on |
Latitude, when plates move they retain same dip from where the rock was formed |
Magnetic Polarity |
- Completely reverses over time
- Important for proving plate tectonics using ocean floor data
- Using rocks by volcano's polarity to show reversed polarity
- "stripes" oriented parallel to seafloor "mountains" |
Trench |
- Subduction zone
- Old ocean floor destroyed |
Mid-Ocean Ridge |
- Spreading center
- New ocean floor created |
Why do plates move? |
- Thermal Convection |
Spreading over time causes... |
stripes of magnetic reversals on sea floor |
If seafloor spreading is occurring... |
age of seafloor should increase away from the spreading center |
Samples from ____ allowed scientists to collect rocks from the ocean floor |
Ocean Drilling program (ODP) |
Why do age bands vary in thickness in different oceans? |
Different rates of seafloor spreading (Pacific Antarctic Ridge fastest at 10cm/yr) |
Seafloor is much ____ than the age of the Earth |
Younger |
Evidence supports the refined theory of plate tectonics? |
- Seafloor spreading
- Symmetric magnetic stripes parallel to mid-ocean ridges
- Depth of ocean Increase away from the ridge
- Thickness of lithosphere Increase away from the ridge
- Age of seafloor is young compared to age of continents |
Divergent boundaries |
- Plates being pulled apart
- Create Ocean Basins
- Plates pull apart - rift valley |
Differences in spreading rates affect shape of ocean bottom Ridges = _____
Rounded = ______ |
Slower
Faster |
Asthenosphere ____ and _____ as it moves away from ridge |
cools, shrinks |
Seafloor ______ as it moves away from ridge |
sinks deeper |
Lithosphere grows _____ over time as it moves away from ridge |
thicker |
Convergent boundaries (Destruction of the Lithosphere) |
- Ocean-Continent
- Subduction
- Ocean-Ocean
- Subduction
- Continent-Continent
- Uplift of sediments |
Ocean-Continent collision |
- Continental Arc Trench Systems
- Melted lithosphere rises and forms a continental arc of volcanoes at the surface
- Andesite - Composition between continent and ocean material |
Ocean- OCean collision |
Island Arc Trench Systems |
Continent-Continent collision |
ex. Himalaya Mountains |
Ocean basins get ____ or are _____ in Convergent boundaries |
smaller, destroyed |
Transform Boundaries |
- Plates move past each other
- No material is created or destroyed |
Transform Boundaries must have |
- Transform faults
- Perpendicular to ridge axis |
Offsets between segments at spreading centers occur along... |
Transform Faults |
Fracture Zones |
Extend beyond the ridge axis |
Volcanic Islands in middle of plates caused by... |
- Hot Spots
- Magma chambers are close to the crust
- Plates move above it
- Hot Spot doesn't move as fast as plate |
Seamounts and table mounts |
- Volcanoes are formed near spreading center
- Fractures (cracks) allow lava to get to the surface
- Volcano dies in 30 mil. years |
Coral reef changes: |
Fringing reef
Barrier reef
Atoll |
Fringing reef |
coral needs shallow water; favorable temperature and salinity |
Barrier reef |
- Landmass starts to subside
- Cooling of lithosphere as it moves from spreading center
- Separated by a lagoon |
Atoll |
- No island-Volcano has subsided below sea level
- Reef contines to grow upward |
North America at equator ____ years ago, Pangea ___ years ago, Atlantic Ocean starts forming ____ years ago, India collies with Asia ____ years ago |
500 mil, 200 mil, 150 mil, 45 mil |
Bathymetry |
topography of the ocean |
How to collect number of depth measurements?
|
Sound Reflection (Sonar) & Satellites |
Density differences between 2 layers cause |
energy reflected, energy transmitted to deeper layers |
____ causes sea level to rise or fall above bathymetric features |
Gravity |
____ leads to extra gravitational attraction on water, which leads to ____ sea levels (water bulges ___) |
Bathymetric high, Higher, upward |
Ship bathymetry vs. satellite bathymetry |
able to be more exact, see minor details |
Passive Margin |
- No seduction
- No plate boundary
- Wide shelves
- slope and rise built seaward |
Active Margin |
- Subduction
- Convergent plate boundary
- Tectonic movement
- Trenches offshore
- Narrow Shelf |
Largest areas on Earth's surface |
- Ocean Basins
- 45% of earth's surface
- Deep water depths
- 2nd coastal plain / Continental shelf
- 27% of earth's surface
- Low elevation- shallow water depth |
Smallest areas on Earth surface |
- Trenches
- 4% of earth's surface
- Mountains
- 8% of earth's surface
- Continental slopes
- 14% of earth's surface |
____ proves activity of turbidity currents in ocean |
Turbidity currents |
Turbidity currents |
cut canyons and form deep-sea fans |
Sea level rise and fall creates ____ sediment deposits in continental slope |
thick |
Highstand sea level |
Trapping on the shelf |
Lowstand sea level |
- Sediment to slope
- Active Caynons |
____ Heated subsurface seawater migrates through cracks in ocean crust |
Hydrothermal vents (30C-350C) |
Hydrothermal vents dissolved ___ precipitate to from ___ sulfide deposits |
metal, metal
- Chemosynthetic
- Able to survive without sunlight |
Types of continental margins _____ & ______ |
active, passive |
Marine Provinces |
Areas of the ocean bottom classified by water depth, slope and process of formation |
Continental margins:
- Shelf
- Slope
- Rise
- Ocean basin
- aBYSSAL pLAIN |
- shallow, flat
- steeper slope
- base of slope
- REALLY FLAT |
Parts of Deep Ocean Basin |
- Ocean Basins (4000 m avg)
- Trenches and volcanic arcs
- Hydrothermal vents |
Why do we care about sediments in the ocean? |
Tells us about climate change and earth's past, present, and future |
Methods of retreiving sediments from seafloor: |
- Dredge: metal net to scoop up rocks
- Gravity corer
- Rotary drilling
- Piston corer |
Classifications of marine sediments |
- Lithogenous ( Land & volcano)
- Biogenous (organism)
- Hydrogenous (water)
- Cosmogenous (outter space) |
Lithogenic Sediments |
- Pre-existing rock, on the continents or volcano
- Transport to ocean through water/air
- Most deposited on Margins |
Sources of Lithogenous sediment |
Rivers, wind glaciers, gravity slides |
Composition of Lithogenous sediments |
- Primarily Quartz |
Classifcation by sediment texture |
- Grain size important in moving sediment
- Erosion
- Transport |
____ the particle, sooner it'll settle. Size is more important than ____ |
larger, density |
Well sorted |
- all grain is the same size
- many transport events before deposition
- Ex. Beaches or sand dunes |
Poorly sorted |
- Few transport events
- Many grain sizes can be moved
- Ex. Glacial deposits |
Grain shape; ____ = less weathered,
____ = more weathered |
angular and jagged, rounded |
Where are lithogenous sediments found? |
- Neritic (near shore to edge of continental shelf)
Beaches, Shelf, Glacial
- Pelagic (deep ocean)
Abyssal clay, Volcanic ash, dust, Deep ocean currents
|
World-wide sediment discharge |
- 20 billion metric tons per year
- 80% from Asian rivers |
Thickest sediments are found near the ____ ______ |
Passive Margins |
Biogenous sediment |
- Macroscopic (shells)
- Microscopic
- shells from microscopic algae
- OOZE (if sediment is .30% biogenic material)
- Not all organisms leave a trace |
Major building blocks "bones" for plankton shells |
Calcium Carbonate, Silica |
Carbonate organisms |
- Calcium carbonate
- Coccolithophores photsynthesize
- Smaller than diatoms (silica); form chalk deposits
- Diatoms - photosynthesizers |
Distribution of biogenous sediments |
- Most common as pelagic deposits |
Factors controlling sediment distribution and composition |
- Productivity
- Destruction (dissolution)
- Dilution |
Where are Biogenous sediments found? |
- Neritic: biogenous material overwhelmed by lithogenous sediment
- Pelagic: oozes (contain at least 30% biogenic material |
Calcareous ooze: |
At least 30% carbonate shells
- preserved in water <4500 m |
Conditions that cause calcite to dissolve |
- Low temp
- Higher pressure
- Higher CO2
- Low pH(more acidic) |
Lysocline |
Depth at which carbonate shells start to dissolve |
_____ ____ ____in ocean, little carbonate material settles and survives below 4500m |
Calcite compensation depth |
Where are Carbonate oozes common? |
Ridges (Mid-ocean ridges) |
How do sea floor sediments record surface ocean conditions? |
- microscopic test sink slowly 10-50 years
- Most biogenous bodies are turned into fecal pellets and fall to seafloor in 10-15 days |
Marine sediments record ocean surface conditions |
Temperature
Nutrient supply
Abundance of marine life
Ocean current patterns
Volcanic eruptions
Change sin climate
Movement of tectonic plates
etc. |
Hydrogenous sediment |
- Derived from dissolved material in water
- Maganese nodules - Mn and Fe |
Other hydrogenous sedimnets |
- Phosphates
- Evaporites |
Mixtures of marine sediments |
Typically one sediment type dominates in different areas of the sea floor |
Global distribution of neritic (near shore) and pelagic (open ocean) surface sediments |
- 48% calcareous ooze
- 38% abyssal clay
- 14% siliceous oozee |