The Sea FloorThe Sea Floor

http://http://www.youtube.com/www.youtube.com/watch?watch?v=SA8tEUGVI_I&fev=SA8tEUGVI_I&feature=relatedature=related(Exploring the (Exploring the deep)deep)

The Water PlanetThe Water Planet

I. The Water PlanetI. The Water PlanetA.A. Geography – oceans make up 71% Geography – oceans make up 71%

of earth’s surface (most in the of earth’s surface (most in the southern hemisphere); 4 major southern hemisphere); 4 major basins (Fig. 2.1 &Table 2.1)basins (Fig. 2.1 &Table 2.1)1. Pacific – deepest & largest1. Pacific – deepest & largest

2. Atlantic 2. Atlantic 3. Indian3. Indian 4. Arctic – smallest & shallowest4. Arctic – smallest & shallowest

Pacific Ocean – Deepest & Pacific Ocean – Deepest & LargestLargest

Atlantic OceanAtlantic Ocean

Indian OceanIndian Ocean

Arctic Ocean – Smallest & Arctic Ocean – Smallest & ShallowestShallowest

I. The Water PlanetI. The Water PlanetB.B. Structure – See Fig. 2.3 – Earth Structure – See Fig. 2.3 – Earth

formed as a result of gravitational formed as a result of gravitational forces attracting particles of dust; forces attracting particles of dust; denser material “sank”denser material “sank”

1. inner core – solid, made up of 1. inner core – solid, made up of mixtures or iron alloysmixtures or iron alloys

2. outer core – liquid – gives earth 2. outer core – liquid – gives earth it’s magnetic fieldit’s magnetic field

3. mantle – solid, but rocks flow like 3. mantle – solid, but rocks flow like water (convection currents) water (convection currents) http://earthguide.ucsd.edu/eoc/teachers/http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_convection2.htmlt_tectonics/p_convection2.html

4. crust – thin; composition differs 4. crust – thin; composition differs between oceans & continentsbetween oceans & continents

5. hydrosphere – free water (most 5. hydrosphere – free water (most contained in oceans)contained in oceans)

6. atmosphere – gaseous covering of 6. atmosphere – gaseous covering of earthearth

Interior of EarthInterior of Earth

Oceanic CrustOceanic Crust Continental CrustContinental Crust 5 km thick5 km thickComposed of basaltComposed of basaltDenser than Denser than continental crustcontinental crustFloats on mantel Floats on mantel Geologically youngGeologically youngRich in iron & Rich in iron & magnesiummagnesium

20 – 50 km thick20 – 50 km thickComposed of Composed of granitegraniteLess DenseLess DenseGeologically olderGeologically olderRich in sodium, Rich in sodium, potassium, calcium & potassium, calcium & aluminumaluminum

II. Origin & Structure of the II. Origin & Structure of the ocean basinsocean basins

A.A. Oceans formed as a result of plate Oceans formed as a result of plate tectonics (Fig. 2.4, 2.5, 2.6)tectonics (Fig. 2.4, 2.5, 2.6)

B. Mid Ocean Ridge – discovered, using sonar, B. Mid Ocean Ridge – discovered, using sonar, during WWII; it is a chain of volcanic during WWII; it is a chain of volcanic submarine mountains that run through submarine mountains that run through ocean basinsocean basins

C. Trenches – deepest parts of the ocean C. Trenches – deepest parts of the ocean floor; associated with active volcanoes & floor; associated with active volcanoes & earthquakesearthquakes

http://www.youtube.com/watch?v=NYbTNFN3NBo&feature=related

D.D. Mid Ocean Ridge/Sea floor spreading Mid Ocean Ridge/Sea floor spreading & Plate tectonics (Fig. 2.7 & 2.8)& Plate tectonics (Fig. 2.7 & 2.8)

1. Sediments get thicker and older 1. Sediments get thicker and older the farther away from the creststhe farther away from the crests

2. magnetic anomalies shows the 2. magnetic anomalies shows the ocean floor developed in stages ocean floor developed in stages http://earthguide.ucsd.edu/eoc/teachehttp://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_paleomag.html rs/t_tectonics/p_paleomag.html

3. Sea Floor spreading – process by 3. Sea Floor spreading – process by which sea floor moves away from the which sea floor moves away from the mid ocean ridges to create new sea mid ocean ridges to create new sea floorfloor

E.E. Plate TectonicsPlate Tectonics 1. Lithospheric plates float on 1. Lithospheric plates float on

mantle & drift at a very slow rate mantle & drift at a very slow rate (Fig. 2.11)(Fig. 2.11)

2. When plates collide trenches are 2. When plates collide trenches are usually formed (Fig. 2.12 & 2.13)usually formed (Fig. 2.12 & 2.13)

3. Subduction – the process where 3. Subduction – the process where a plate descends into the mantle & a plate descends into the mantle & melts; produces earthquakes & melts; produces earthquakes & volcanic eruptionsvolcanic eruptions

• http://earthguide.ucsd.edu/eoc/http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/teachers/t_tectonics/p_subduction.htmlp_subduction.html

• http://earthguide.ucsd.edu/eoc/http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_hawaii.html teachers/t_tectonics/p_hawaii.html ((Hawaiian-Emperor seamount Hawaiian-Emperor seamount chain)chain)

http://www.youtube.com/watch?http://www.youtube.com/watch?v=ngV66m00UvU&NR=1v=ngV66m00UvU&NR=1

Shear boundary – two Shear boundary – two plates slide past each plates slide past each otherother

F.F. Geolocigal History of the EarthGeolocigal History of the Earth 1. Atlantic is growing, Pacific is shrinking 1. Atlantic is growing, Pacific is shrinking 2 Analysis of sediments can give clues to 2 Analysis of sediments can give clues to

oceans history (Fig. 2.4)oceans history (Fig. 2.4) 3. Sea levels decrease during glaciation 3. Sea levels decrease during glaciation

and increase during warming and increase during warming 4. Sea surface temperatures decrease4. Sea surface temperatures decrease

during glaciation and increase duringduring glaciation and increase during interglacial periodsinterglacial periods

III. Geological Provinces of III. Geological Provinces of OceanOceanA.A. Continental Margins – boundaries Continental Margins – boundaries

between continental crust & oceanic between continental crust & oceanic crustcrust

1. Continental shelf – shallow gentle 1. Continental shelf – shallow gentle slope; biologically richest part of the slope; biologically richest part of the ocean; ends at shelf break (slope ocean; ends at shelf break (slope abruptly gets steeper – Fig. 2.19)abruptly gets steeper – Fig. 2.19)

2. Continental slope – “edge” of continent2. Continental slope – “edge” of continent 3. Continental rise – area where 3. Continental rise – area where

sediments build up on sea floor at base sediments build up on sea floor at base of continental slopeof continental slope

Active Margins Vs. Passive Active Margins Vs. Passive marginsmarginsActive Margins are geologically more Active Margins are geologically more

active than passive marginsactive than passive marginsActive Margins have little or no shelf as Active Margins have little or no shelf as

compared to the wide gentle slope of compared to the wide gentle slope of passive marginspassive margins

See Fig. 2-22See Fig. 2-22

East coast of theEast coast of theU.S. – passiveU.S. – passivemarginmargin

Little or no shelfLittle or no shelf

Active MarginActive Margin

Steep slopeSteep slope

No RiseNo Rise

Active Active MarginMargin

• Seamounts are submarine volcanoes Seamounts are submarine volcanoes that have great biodiversity that have great biodiversity http://www.youtube.com/watch?http://www.youtube.com/watch?v=5rb5HzR26OMv=5rb5HzR26OM

Hydrothermal vents are areas near the mid Hydrothermal vents are areas near the mid ocean ridge where water seeps into gaps, is ocean ridge where water seeps into gaps, is heated, and then makes its way back up heated, and then makes its way back up through the crustthrough the crusthttp://video.nationalgeographic.com/video/ehttp://video.nationalgeographic.com/video/environment/habitats-environment/habitats-nvironment/habitats-environment/habitats-oceans-env/hydrothermal-vents/oceans-env/hydrothermal-vents/