Where is Andros??

Mercator Projection

World Ocean

What is the inner core made of? Iron Why? Because it is very dense and pulled to center by gravity

What is the upper mantle ? Solid or Liquid?

Which is the highest density? Ocean crust Or Continental Crust

Process is called Plate Tectonics Proposed by Alfred Wagner 1880-1930 Less dense (lighter) continental plates float on heavier oceanic plates

What is the energy source that moves the plates??? Convection Currents- heated material expands (becomes less dense) and is forced up by heavier (more dense) material. “Blanket Effect” – Super continent, Pangea, insulated hot interior, causing heat build up and convection currents. Plates are drug along by this movement

Convection currents moving plates and forming new land at oceanic ridges

Cindy Ebinger –plate tectonics Studies rift zones.. Has done most of her work in Ethiopia, East Africa

Rift photo by Ebinger in Ethiopia

Plates move apart 8-12 cm/year Fingernails grow 6 cm/year

Rift in Iceland

Youngest rock at the center – oldest rock farthest from the center (rift valleys)

Facts that support continental drift 1. Similar shaped continents

2. Similar fossils across Atlantic

3. Magnetic Reversals

Sediment deepest at edges of continents – thinnest at ridge (dust settling on ocean surface)

5.Youngest rocks are at the center and rocks at the edges of the Atlantic are 150 million years old

Active Margin Plates running into each other Volcanoes, mountain building, earthquakes

Subduction –one plate moves under the other Volcano 100 km from trench

South America is moving west colliding with Nazca plate Trench ↑ ↑ Mountains

Passive Margin Growing plates

Volcanic Islands are found only at ACTIVE plate boundaries Forms LITHOGENIC SEDIMENT- break up of rocks (Quartz) Andros no Quartz –no volcano Biogenic sediment Made of skeletons and shells of marine organisms

Why study plate tectonics? What do you find at active boundaries? Minerals – Iron – Oil – Gold - Diamonds Present active boundaries are easy to find, finding active boundaries pre-dating Pangea requires a lot of study

Active Plate Margin vs Passive Plate Margin Active Margin- little or no shelf (shelf is crushed by movement) therefore minimal amount of fishing (no shallow water for plants), EXEPT at upwellings Passive plate margin- very wide shelf Therefore (shallow water for plants) major fishing, because of shallow water

Shelf is only 8% of the ocean’s surface, but the most valuable. Average width 40 miles Average depth 197 feet Slope is undetectable to eye (flat because turbidity (Mud) currents from rivers level out the slope Biologically riches part of the ocean

Divisions of oceans Benthic – Pelagic – Topography of the ocean bottom Water environment

Pelagic divisions Photic – Aphotic – Lighted areas where photosynthesis takes place Aphotic – Light does NOT penetrate

Pelagic (water) environment divided by depth Neritic – water near the shore Oceanic—water beyond the shelf Deep Ocean – ocean floor

Neritic (near shore) Large variety of conditions Salinity changes caused by: Evaporation Dilution from freshwater rivers Temperature changes- water depth MOST BIOLOGICALLY PRODUCTIVE PART OF THE SEA

Oceanic (beyond the shelf) Conditions are more constant Slow moving currents Temperature constant (except in thermoclines)

Bathyal – edge of shelf Abyssal – deep ocean Hadal – trenches

Environment of Deep Ocean High water pressure?? Organisms are primarily H2O, because water is not compressible like air Food ?? No light – no plants ?? Most of food falls from the surface Oxygen ?? No light – no plants ?? O2 is brought down by cold water density currents

Sea level has risen twice in the last 30,000 years. Why has sea level changed???? Glaciers change sea level