The Sea Floor

• Q: Of the Norhern and Southern Hemisphere, Q: Of the Norhern and Southern Hemisphere, which one contains the most water??which one contains the most water??

• A: Right! The Southern Hemisphere contains A: Right! The Southern Hemisphere contains nearly 80% water by volume. nearly 80% water by volume.

• Q: Which ocean is the largest? The deepest?Q: Which ocean is the largest? The deepest?a. Arctic b. Pacific c. Atlantic d. Indiana. Arctic b. Pacific c. Atlantic d. Indian

• A: PacificA: Pacific

• A: Pacific again!A: Pacific again!

Brain Warmers:Brain Warmers:

Figure 2.02Figure 2.02

• Big bangBig bang leftovers! leftovers!

• Density played a major role.Density played a major role.

• How’s that work??How’s that work??

• Density = mass/volumeDensity = mass/volume

• Lighter stuff stays on the top!Lighter stuff stays on the top!

How did it all get this way?How did it all get this way?

Figure 2.03Figure 2.03

• Ocean crust is composed of Ocean crust is composed of basaltbasalt. Basalt is . Basalt is common to the sea floor also.common to the sea floor also.

• Much of the crust which forms land masses is Much of the crust which forms land masses is composed of composed of granitegranite..

• Much of the ocean floor and crust differs in Much of the ocean floor and crust differs in age too! (200 myo compared to 3.8 byo!!)age too! (200 myo compared to 3.8 byo!!)

• Why??Why??

Ocean Floor FactsOcean Floor Facts

• Sir Francis Bacon (1620) considered contents Sir Francis Bacon (1620) considered contents puzzle pieces.puzzle pieces.

• Geological features (coal deposits) matched on Geological features (coal deposits) matched on opposite coasts.opposite coasts.

Ocean Floor StructureOcean Floor Structure

Figure 2.04Figure 2.04

• Sir Francis Bacon (1620) considered contents Sir Francis Bacon (1620) considered contents puzzle pieces.puzzle pieces.

• Geological features (coal deposits) matched on Geological features (coal deposits) matched on opposite coasts.opposite coasts.

• Alfred Wegner (1912) hypothesized Alfred Wegner (1912) hypothesized continental drift.continental drift.

Ocean Floor StructureOcean Floor Structure

• Continents may have been one Continents may have been one piece which later broke appart, piece which later broke appart, moved, and formed present moved, and formed present day conditions.day conditions.

• How??How??

• Plate tectonics Plate tectonics ocean floor ocean floor movement.movement.

• Consists of Consists of faultsfaults (cracks) (cracks) which form the which form the mid ocean mid ocean ridges (mountains)ridges (mountains). .

Pangea Bound…Pangea Bound…180 mya

150 mya

95 mya

45 mya

15 mya

Figure 2.05Figure 2.05

Current Mid-ocean ridges & trenchesCurrent Mid-ocean ridges & trenches

Figure 2.06Figure 2.06

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

Figure 2.07Figure 2.07

Figure 2.08Figure 2.08

• Sea floor spreading occurs at Sea floor spreading occurs at mid-ocean ridges.mid-ocean ridges.

• Magnetic anomaliesMagnetic anomalies occur here too! occur here too!

““Okay, Dr. K. You’re using Okay, Dr. K. You’re using big words again!!”big words again!!”

Magnetic anemone!! But seriously….Magnetic anemone!! But seriously….

•Sea-floor spreadingSea-floor spreading where the ocean floor where the ocean floor moves away from moves away from the mid-ocean ridgethe mid-ocean ridgerecords the magneticrecords the magneticfields of the earth.fields of the earth.

•

Figure 2.10Figure 2.10

Locations and direction of seafloor spreading. Locations and direction of seafloor spreading.

Figure 2.11Figure 2.11

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

Figure 2.12Figure 2.12

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

Figure 2.13Figure 2.13

Some areas can be quite acitve!!

Mt. Veniaminof, Alaska

Figure 2.14Figure 2.14

When plates move When plates move sideways then a newsideways then a newformation called a formation called a shear-boundaryshear-boundary..

San Andreas Fault, CASan Andreas Fault, CA

Figure 2.15Figure 2.15

Swirlling vs. PullingSwirlling vs. PullingConvection suggests that continents move on a “soup” of rock, Convection suggests that continents move on a “soup” of rock, Whearas Whearas slab pullingslab pulling indicates that as rock cools, it sink beneath indicates that as rock cools, it sink beneaththe surface and “pulls” lithosphere into the depths (This is the the surface and “pulls” lithosphere into the depths (This is the currently accepted explanation.) currently accepted explanation.)

Figure 2.17Figure 2.17

Ocean sediments often preserve organism which help Ocean sediments often preserve organism which help scientist age the ocean floor. scientist age the ocean floor.

Lithogenous sedimentLithogenous sediment contains minerals, whilecontains minerals, while biogenous biogenous sediment contains fossil remains.sediment contains fossil remains.

Figure 2.19Figure 2.19

Figure 2.20Figure 2.20

Figure 2.21Figure 2.21

Figure 2.22Figure 2.22

Figure 2.23Figure 2.23

Figure 2.24Figure 2.24

Figure 2.25Figure 2.25

Figure 2.26Figure 2.26

Figure 2.27Figure 2.27

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