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The Sea Floor. Q: Of the Norhern 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
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Q: Of the Norhern 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! Brain Warmers:
Big bang leftovers! • Density played a major role. • How’s that work?? • Density = mass/volume • Lighter stuff stays on the top! How did it all get this way?
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?? Ocean Floor Facts
Sir Francis Bacon (1620) considered contents puzzle pieces. • Geological features (coal deposits) matched on opposite coasts. 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. Ocean Floor Structure
Continents may have been one piece which later broke appart, moved, and formed present day conditions. • How?? • Plate tectonics ocean floor movement. • Consists of faults (cracks) which form the mid ocean ridges (mountains). 180 mya Pangea Bound… 150 mya 95 mya 45 mya 15 mya
Figure 2.05 Current Mid-ocean ridges & trenches
Figure 2.06 These locations are a significant source of geological activity!
Figure 2.08 • Sea floor spreading occurs at • mid-ocean ridges. • Magnetic anomalies occur here too! • “Okay, Dr. K. You’re using • big words again!!”
Sea-floor spreading • where the ocean floor • moves away from • the mid-ocean ridge • records the magnetic • fields of the earth.
Figure 2.10 Locations and direction of seafloor spreading.
Figure 2.11 Crust and mantle come together to form the lithosphere. Subduction and resulting subduction zones where ocean floor plates flow beneath the mantle of the crust are places of tectonic activity.
Figure 2.12 Trenches and island arcs can be formed when two sections of ocean plates come together.
Figure 2.13 Mt. Veniaminof, Alaska Some areas can be quite acitve!!
Figure 2.14 When plates move sideways then a new formation called a shear-boundary. San Andreas Fault, CA
Figure 2.15 Swirlling vs. Pulling Convection suggests that continents move on a “soup” of rock, Whearas slab pulling indicates that as rock cools, it sink beneath the surface and “pulls” lithosphere into the depths (This is the currently accepted explanation.)
Figure 2.17 Ocean sediments often preserve organism which help scientist age the ocean floor. Lithogenous sedimentcontains minerals, while biogenous sediment contains fossil remains.
