The Sea Floor

A: Right! The Southern Hemisphere contains nearly 80% water by volume. Brain Warmers: Q: Of the Northern and Southern Hemisphere, which one contains the most water?? A: Right! The Southern Hemisphere contains nearly 80% water by volume. Q: Which ocean is the largest? The deepest? a. Arctic b. Pacific c. Atlantic d. Indian A: Pacific A: Pacific again!

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How did it all get this way? Big bang leftovers! Density played a major role. How’s that work?? Density = mass/volume Lighter stuff stays on the top!

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Ocean Floor Facts Ocean crust is composed of basalt. Basalt is common to the sea floor also. Much of the crust which forms land masses is composed of granite. Much of the ocean floor and crust differs in age too! (200 myo compared to 3.8 byo!!) Why??

About what percent of the Earth’s surface is covered by ocean? 50% 71% 85% 25%

Which is true? The Pacific ocean is deepest and smallest The Arctic ocean is shallowest and smallest The Atlantic ocean is deepest and largest The Indian ocean is shallowest and largest

Ocean Floor Structure Sir Francis Bacon (1620) considered continents puzzle pieces. Geological features (coal deposits) matched on opposite coasts.

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Ocean Floor Structure Sir Francis Bacon (1620) considered contents puzzle pieces. Geological features (coal deposits) matched on opposite coasts. Alfred Wegner (1912) hypothesized continental drift.

180 mya Pangea Bound… Continents may have been one piece which later broke apart, moved, and formed present day conditions. How?? Plate tectonics ocean floor movement. Consists of faults (cracks) which form the mid ocean ridges (mountains). 150 mya 95 mya 45 mya 15 mya

Current Mid-ocean ridges & trenches Figure 2.05 Current Mid-ocean ridges & trenches

http://www.youtube.com/watch?v=K8blL9Ki2mQ

These locations are a significant source of geological activity! Figure 2.06 These locations are a significant source of geological activity!

http://www.youtube.com/watch?v=v5DG5Eup9ss

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http://www.youtube.com/watch?v=hmMlspNoZMs

Magnetic anomalies occur here too! Figure 2.08 Sea floor spreading occurs at mid-ocean ridges. Magnetic anomalies occur here too! “Okay, Miss Collins. You’re using big words again!!”

Magnetic anemone!! But seriously….

Sea-floor spreading where the ocean floor moves away from the mid-ocean ridge records the magnetic fields of the earth.

Locations and direction of seafloor spreading. Figure 2.10 Locations and direction of seafloor spreading.

Crust and mantle come together to form the lithosphere. Figure 2.11 Crust and mantle come together to form the lithosphere. Subduction, and resulting subduction zones, are where ocean floor plates flow beneath the mantle of the crust and are places of tectonic activity.

Trenches and island arcs can be formed when two sections of ocean Figure 2.12 Trenches and island arcs can be formed when two sections of ocean plates come together.

Some areas can be quite active!! Figure 2.13 Mt. Veniaminof, Alaska Some areas can be quite active!!

sideways then there is a new formation called a shear-boundary. Figure 2.14 When plates move sideways then there is a new formation called a shear-boundary. San Andreas Fault, CA

Figure 2.15 Swirling vs. Pulling Convection suggests that continents move on a “soup” of rock, whereas slab pulling indicates that as rock cools, it sinks beneath the surface and “pulls” lithosphere into the depths (This is the currently accepted explanation.)

Magnetic anomalies are bands of rock that run parallel to the mid-ocean ridge system. What do they provide evidence for? Bacteria lived in the ocean floor millions of years ago Volcanoes form at ocean ridges. The sea floor was formed in layers Granite is denser than basalt

Continental plates are believed to move because of which of these causes? New volcanic rock pushes them away from spreading centers. Cooling lithosphere becomes dense, sinks, and pulls a plate with it. Plates crack along fault lines. The mantle is fluid and carries plates along with it

Ocean sediments often preserve organisms which help Figure 2.17 Ocean sediments often preserve organisms which help scientists age the ocean floor. Lithogenous sediment contains minerals, while biogenous sediment contains fossil remains.

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The biologically richest area of the seafloor is The continental shelf. The continental slope. The plain. Deep-sea vents. The abyssal plain

Red clay is an example of biogenous sediment. True False

A swimmer sees a shark. Some sharks are dangerous A swimmer sees a shark. Some sharks are dangerous. The swimmer swims away from the shark based on this information. Tested a hypothesis Used inductive reasoning Formed a theory Used deductive reasoning

Which of the following is a valid scientific hypothesis? Dogs are superior pets. It is immoral to keep whales in captivity. Dolphins use brainwaves to communicate. One-spot foxface rabbitfish prefer green algae to red algae.

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http://www.youtube.com/watch?v=GyMLlLxbfa4

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