Unit 4 & 5 Geology of the Ocean, Water, Waves, and Tides MRS. STAHL MARINE BIOLOGY
Some Facts Solar system was formed more than 5 billion years ago, with Earth forming 400 million years later. Surface was so hot that water could not remain there because there was no free oxygen gas in the atmosphere Ocean began forming 4.2 billion years ago Life first evolved in the ocean Ocean covers 70.8%
How did the ocean form? Hypothesis is: Earth was composed of cold matter and over time energy from space and radioactive decay causes the temperatures to rise. Process continued for several hundred million years until the core of the Earth was hot enough to melt iron and nickel. Elements melted -> moved to the core-> raising temps to 2,000 C Molten material moved to the surface and spread out, continued to melt and solidify, creating our landscape separating the lighter elements from the denser ones.
They think that if there was any water present it was stored up in the Earth s minerals. Then continuous heating and cooling took place and water vapor was carried to the surface, it cooled, condensed, and formed the ocean!
Video http://www.history.com/shows/how-the-earth-wasmade/videos/oceans
Origin of Life Atmosphere was originally made up of gases like carbon monoxide, carbon dioxide, methane, nitrogen, and ammonia. Oxygen is chemically active so any other free oxygen gas present would have combined with some other element forming oxides. Therefore, oxygen did not start to accumulate in the atmosphere until the evolution of modern photosynthesis. Oxides- Chemical compound containing at least one oxygen atom as well as another element.
Biologists also theorize that the molecules (carbon monoxide, carbon dioxide, nitrogen, methane, and ammonia) formed and accumulated in the ocean and over time the ocean turned into a huge, highly concentrated bowl of nutrient soup.
The molecules then became organized and the first cells evolved. There wasn t any oxygen so the first cells had to be anaerobic. The first cells were also heterotrophs or relied on others for food.
The oldest marine fossil is marine bacteria (cyanobacteria), was found in NW Australia, and is estimated to be between 3.4 and 3.5 billion years old.
The Ocean Today
The Ocean Today 139 million square miles, 362 X 10^18 gallons 362,000,000,000,000,000,000 gallons of water Largest habitat on the planet Referred to as the world ocean
There are four major basins, but five oceans 1.Pacific 2.Atlantic 3.Indian 4.Arctic
The area around Antarctica is referred to as the Southern or Antarctic
Body of Water Define Examples Sea Gulf Body of saltwater that is smaller than an ocean and landlocked. Smaller body of water that is mostly cut off from the larger ocean or sea by land formations. Mediterranean Sea Red Sea Caribbean Sea Gulf of California Gulf of Mexico Persian Gulf
Continental Drift The movement of the seafloor caused by the continuous movement o the continents that rest on it.
The seafloor is constantly being replaced with new seafloor, therefore, organisms have to adapt constantly.
Lithosphere - Rock Sphere - Tectonic plate - Very strong Asthenosphere - Weak - Easily deformed layer of the Earth - Acts as a lubricant for the plates to slide
Oceanic Crust Continental Crust - Basalt - Thin crust under the oceans - Thinner and denser - Granite - Floats on top of mantle - Makes up the continents - More active
Moving Continents Timeline of Moving Continents Early 1600 s Sir Frances Bacon Continents may have once been connected to each other. Proposed Gondwanaland- fusion of Southern Continents (S. America, Africa, India, Antarctica, and Australia). 1915 Alfred Wegener Molten rock / Magma in the mantle moved by convection currents (heating and cooling of magma). 19 th Century Edward Suess One supercontinent= Pangaea. Forces of the Earth s rotation separated the continents. 1960 s H.H. Hess
Pangaea
The man of Pangaea is Alfred Wegener
Evidence of Continental Drift 1. Continental plates fit together like a puzzle. 2. Distribution of Earthquakes -> occur in narrow zones that correspond to areas along ridges and trenches. Most active areas of crustal movement.
3. Temperature of Sea Bottom-> highest temps at ridges. Temps decrease with distance from ridges. Why do you think that is????? Heating magma oozing out.
4. Age of rock samples from seafloor. Youngest rock was found near ridges and older rocks were found further away. 5. Fossils collected on opposite coasts were similar.
6. Coal deposits and other geological formations matched up on opposite sides of the Atlantic. 7. Sediment gets thicker and thicker as you move away from the ridges.
8. Seafloor Spreading-> basalt magma from the mantle rises to create new ocean floor at midocean ridges. On each side of the ridge, sea floor moves from the ridge towards the deep sea trenches, where it is subducted or sucked back into and recycled back into the mantle
9. Magnetic evidence-> * 170 reversals in the past 76 million years (north / south polarity switched back and forth). Reverses directions. * Caused by fluctuations in the movement of material in iron-nickel outer core. * When rocks are in the molten stage they are free to move around and act like tiny little compasses pointing either north or south. * When the rocks cool they keep whatever their orientation is. There are literally stripes on the rocks that show the magnetic bands and they match up on either side of the mid ocean ridge= magnetic anomalies.
Continental Drift was not accepted at first because: Scientists thought that he did not have enough evidence to prove his theory.
Laurasia consisted of: Europe, Asia, and North America Gondwanaland- S. America, Africa, India, Antarctica, and Australia
The Forces that Drive Continental Movement HH Hess Convection currents- the way magma moves. Magma rises from the Earth s core to the upper mantle, because it s less dense than the surrounding material. When it reaches the mantle it cools, becomes denser, and sinks back into the core. The recycling causes changes in temperature called convection. Volcanoes form when the magma breaks through the Earth s crust. Lines of volcanoes form underwater mountain ranges = midocean ridges When it cools, it forms new crust = oceanic basaltic crust https://www.youtube.com/watch?v=mmmx83diwl0
Rift Valley Where the Earth s crust is splitting apart Narrow, steep sides, flat floor Looks like a ditch Created by tectonic activity High volcanic activity.
Tanzania s Great Rift Valley
Fracture Zones- Linear regions of unusually irregular sea bottom. Almost like cracks in the crust
SUBDUCTION ZONES Regions where the old material sinks down into the mantle, and when it hits the magma of the mantle, it liquefies and recycles itself through convection currents, back into the core.
Seafloor Spreading Oceanic plates are diverging from one another, the magma rises along a rift zone and spreads out at the surface building new seafloor. The age of the rocks increases as one moves away from the rift zone. The midoceanic ridge is the primary site for seafloor spreading. Earthquakes and volcanoes are where seafloor spreading is occurring.
Theory of Plate Tectonics The lithosphere is viewed as a series of rigid plates that are separated by earthquake belts that are located around trenches, ridges, and faults.
Seven Major Plates are: 1._Pacific 2. North American 3. Eurasian 4. South American 5. African 6. Antarctic 7. Australian
Where plate boundaries move apart and new lithosphere is formed divergent plate boundaries occur. Where the old lithosphere is destroyed because the plates move toward each is called convergent plate boundaries. Where the plates move past each other = Faults.
Transform Fault Special kind of fault that is found in sections of the midocean ridge. Each side is formed by a different plate and the plates scrape against each other
Divergent Boundary- plates move away from each other Produce earthquakes and volcanoes When they pull apart= earthquakes Magma increases = volcano Magnetic anomalies= proves that the ocean plates are moving. Mid-ocean ridges are created Mid-Atlantic Ridge (moves N. America and Europe further apart) Convection Currents Seafloor Spreading
Convergent Boundary- plates move together Produce mountain chains= earthquakes Subduction zone-> oceanic crust subducts back into the mantle Ring of Fire Continental crust is buoyant and less dense so one plate doesn t easily override another. Himalayas-> Indo-Australian Plate pushes into the Eurasian Plate (India vs. China)
Transform Fault- plates slide past each other Earthquakes San Andreas Fault in CA (where the N. American and Pacific plates) Mid-ocean ridge https://www.youtube.com/watch?v=jmc-vjqgsnm
Rift Zones Where the lithosphere splits, separates, and moves apart, as new crust is formed.
Rift Communities / Deep Sea Vents Thriving communities of marine organisms Depend on chemosynthetic activity of bacteria for their nutrients. Represent food webs that exist in the absence of sunlight. https://ocean.si.edu/oceanvideos/hydrothermal-vent-creatures
The Ocean Bottom
Bathygraphic Features Physical features of the ocean bottom
The ocean bottom is divided into two different regions the continental margin and the ocean basin.
Continental Margins Region that lies beneath the neritic zone. Consists of continental shelf and continental slope Composed of granite that is covered by sediment and have similar features to the edge of the nearby continent. See Figure 3-12 on page 56 to discuss the formation of the continental shelf.
Continental Shelf Generally flat areas 40 miles wide and 430 feet deep Slopes gently toward the bottom of the ocean basin Produced by waves that constantly erode land mass and by natural dams, reefs, rocks, and volcanic barriers.
Continental Slope Transitional level Shelf break is where the shelf ends and the slope begins Shelf break is where there is a rapid change in depth to the seafloor Less sediment Submarine Canyons-> aligned with river systems on land and they create a ripple effect on the sea floor. At the end it fans out = Deep Sea Fan. They are formed by turbidity currents = underwater avalanches of sediment (large accumulations of sediment collapse).
Continental Rise Small slope at the base of the continental slope. Created by landslides that carry sediment to the bottom of the slope.
The Ocean Basin: Seafloor Four Main basins: Pacific, Atlantic, Indian, and Arctic Composed of Basalt Rock covered with a thick blanket of sediment.
Abyssal Plains and Hills Bottom of the ocean basin Flat Formed by sediment from turbidity currents Spread out on the ocean floor are abyssal hills (3300 ft. high). Formed by volcanic activity
Seamounts Steep sided formation that rises sharply from the bottom. Formed by underwater volcanoes Some show us coral reef activity and erosion proving that they may have been above water at one point in time.
Ridges and Rises Series of large, underwater volcanic mountains that run through every ocean. Separates the ocean basins
Trenches Most common in the Pacific Ocean Marianas Trench-> the deepest spot on the Earth is the Challenger Deep and is 6.85 miles deep.
The Ocean Floor Continental shelf is very productive because it relatively shallow and provides lots of sunlight and nutrients. Abundant marine life on the shelf No sunlight in the abyss. Limited to chemosynthetic bacteria in vent communities Ocean floor organisms rely heavily on organisms falling from above.
Composition of the Seafloor The entire seafloor is made up of basalt rock with a blanket of sediment on top. Sediment is made up of: Living organisms Land Atmosphere Sea that accumulates over time
Why is the sediment so important to organisms that live on the continental slope, shelf, or abyssal plains? Provides a habitat for many organisms and a source of nutrients for others.
Five types of sediment: Biogenous Hydrogenous Terrigenous Cosmogenous Lithogenous
Hydrogenous Forms when dissolved materials come out of a solution such as a precipitate. Precipitation is caused by changes in temperature, pressure, and chemically active fluids. Types include manganese nodules (ore material in the ocean that comes from terrigenous and volcanic, and also hydrothermal material), phosphates, evaporative salts, metal sulfides, and carbonates (rocks with high amounts of calcium).
Lithogenous Composed of fragments of Pre-existing rock material Formed by Physical and Chemical Weathering- > break-up of exposed rock, movement of sediment, and large particles of rock that are deposited near the edges of the continents and it accumulates Most is made up of quartz Where is it found? -> Neritic zone (near shore), beaches, continental shelves, pelagic zones (deep sea floor).
Biogenous Skeletons and shells of dead marine organisms. Biogenous ooze= made up of 30% of microscopic shells. When it hardens it turns into rock and can make chalk or diatomaceous earth. Calcareous ooze= calcium carbonate= coccolithophorians and foraminiferans Silicareous ooze= silica= radiolarians and diatoms Found in the pelagic zone
Foraminiferans
Coccolithophorians
Radiolarians
Diatoms
Terrigenous Found in the deep sea and is formed by accumulation of turbidites Turbidites are sea-bottom deposits formed by massive slope failures where rivers have deposited large deltas. These slopes fail in response to earthquake shaking or excessive sedimentation
Turbidites
Cosmogenous Composed of material from outer space Space dust and meteor debris Forms an insignificant amount of ocean sediment