The Sea Floor om/watch?v=SA8tEUG VI_I&feature=related om/watch?v=SA8tEUG VI_I&feature=related (Exploring the deep)

The Water Planet The Water Planet

I. The Water Planet A. Geography – oceans make up 71% of earth’s surface (most in the southern hemisphere); 4 major basins (Fig. 2.1 &Table 2.1) 1. Pacific – deepest & largest 2. Atlantic 2. Atlantic 3. Indian 3. Indian 4. Arctic – smallest & shallowest 4. Arctic – smallest & shallowest

Pacific Ocean – Deepest & Largest

Atlantic Ocean

Indian Ocean

Arctic Ocean – Smallest & Shallowest

I. The Water Planet B. Structure – See Fig. 2.3 – Earth formed as a result of gravitational forces attracting particles of dust; denser material “sank” 1. inner core – solid, made up of mixtures or iron alloys 1. inner core – solid, made up of mixtures or iron alloys 2. outer core – liquid – gives earth it’s magnetic field 2. outer core – liquid – gives earth it’s magnetic field

3. mantle – solid, but rocks flow like water (convection currents) _tectonics/p_convection2.html 3. mantle – solid, but rocks flow like water (convection currents) _tectonics/p_convection2.html _tectonics/p_convection2.html _tectonics/p_convection2.html 4. crust – thin; composition differs between oceans & continents 4. crust – thin; composition differs between oceans & continents 5. hydrosphere – free water (most contained in oceans) 5. hydrosphere – free water (most contained in oceans) 6. atmosphere – gaseous covering of earth 6. atmosphere – gaseous covering of earth

Interior of Earth

Oceanic Crust Continental Crust 5 km thick 5 km thick Composed of basalt Composed of basalt Denser than continental crust Denser than continental crust Floats on mantel Floats on mantel Geologically young Geologically young Rich in iron & magnesium Rich in iron & magnesium 20 – 50 km thick 20 – 50 km thick Composed of granite Composed of granite Less Dense Less Dense Geologically older Geologically older Rich in sodium, potassium, calcium & aluminum Rich in sodium, potassium, calcium & aluminum

II. Origin & Structure of the ocean basins A. Oceans formed as a result of plate tectonics (Fig. 2.4, 2.5, 2.6) B. Mid Ocean Ridge – discovered, using sonar, during WWII; it is a chain of volcanic submarine mountains that run through ocean basins C. Trenches – deepest parts of the ocean floor; associated with active volcanoes & earthquakes

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D. Mid Ocean Ridge/Sea floor spreading & Plate tectonics (Fig. 2.7 & 2.8) 1. Sediments get thicker and older the farther away from the crests 1. Sediments get thicker and older the farther away from the crests 2. magnetic anomalies shows the ocean floor developed in stages /t_tectonics/p_paleomag.html 2. magnetic anomalies shows the ocean floor developed in stages /t_tectonics/p_paleomag.html /t_tectonics/p_paleomag.html /t_tectonics/p_paleomag.html 3. Sea Floor spreading – process by which sea floor moves away from the mid ocean ridges to create new sea floor 3. Sea Floor spreading – process by which sea floor moves away from the mid ocean ridges to create new sea floor

E. Plate Tectonics 1. Lithospheric plates float on mantle & drift at a very slow rate (Fig. 2.11) 1. Lithospheric plates float on mantle & drift at a very slow rate (Fig. 2.11) 2. When plates collide trenches are usually formed (Fig & 2.13) 2. When plates collide trenches are usually formed (Fig & 2.13) 3. Subduction – the process where a plate descends into the mantle & melts; produces earthquakes & volcanic eruptions 3. Subduction – the process where a plate descends into the mantle & melts; produces earthquakes & volcanic eruptions

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_tectonics/p_hawaii.html (Hawaiian- Emperor seamount chain) _tectonics/p_hawaii.html (Hawaiian- Emperor seamount chain) _tectonics/p_hawaii.html _tectonics/p_hawaii.html

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Shear boundary – two plates slide past each other

F. Geolocigal 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 oceans history (Fig. 2.4) 2 Analysis of sediments can give clues to oceans history (Fig. 2.4) 3. Sea levels decrease during glaciation and increase during warming 3. Sea levels decrease during glaciation and increase during warming 4. Sea surface temperatures decrease during glaciation and increase during during glaciation and increase during interglacial periods interglacial periods

III. Geological Provinces of Ocean A. Continental Margins – boundaries between continental crust & oceanic crust 1. Continental shelf – shallow gentle slope; biologically richest part of the ocean; ends at shelf break (slope abruptly gets steeper – Fig. 2.19) 1. Continental shelf – shallow gentle slope; biologically richest part of the ocean; ends at shelf break (slope abruptly gets steeper – Fig. 2.19) 2. Continental slope – “edge” of continent 2. Continental slope – “edge” of continent 3. Continental rise – area where sediments build up on sea floor at base of continental slope 3. Continental rise – area where sediments build up on sea floor at base of continental slope

Active Margins Vs. Passive margins Active Margins are geologically more active than passive margins Active Margins have little or no shelf as compared to the wide gentle slope of passive margins See Fig. 2-22

East coast of the U.S. – passive margin

Little or no shelf Active Margin Steep slope No Rise

Active Margin

Seamounts are submarine volcanoes that have great biodiversity zR26OM Seamounts are submarine volcanoes that have great biodiversity zR26OM zR26OM zR26OM

Hydrothermal vents are areas near the mid ocean ridge where water seeps into gaps, is heated, and then makes its way back up through the crust ment/habitats-environment/habitats-oceans- env/hydrothermal-vents/ ment/habitats-environment/habitats-oceans- env/hydrothermal-vents/ ment/habitats-environment/habitats-oceans- env/hydrothermal-vents/