Where is Where is Andros??Andros??

Mercator ProjectionMercator Projection

World OceanWorld Ocean

What is the inner core made of?What is the inner core made of?

Why?Why?Because it is very dense and pulled to center by gravity

IronIron

What is the upper mantle ?What is the upper mantle ?

Solid or Solid or Liquid?Liquid?

Which is the highest density?Which is the highest density?

Ocean crustOcean crustOr Or Continental Continental

CrustCrust

Process is called Plate TectonicsProcess is called Plate Tectonics

Proposed byProposed by– Alfred WagnerAlfred Wagner– 1880-19301880-1930

Less dense Less dense (lighter) (lighter) continental plates continental plates float on heavier float on heavier oceanic platesoceanic plates

What is the energy source that What is the energy source that moves the plates???moves the plates???

Convection Currents- heated material Convection Currents- heated material expands (becomes less dense) and is expands (becomes less dense) and is forced up by heavier (more dense) material.forced up by heavier (more dense) material.

““Blanket Effect” – Super continent, Blanket Effect” – Super continent, Pangea, insulated hot interior, causing Pangea, insulated hot interior, causing heat build up and convection currents.heat build up and convection currents.Plates are drug along by this movementPlates are drug along by this movement

Convection currents moving Convection currents moving plates and forming new land at plates and forming new land at

oceanic ridgesoceanic ridges

Cindy Ebinger –plate tectonics Cindy Ebinger –plate tectonics

Studies rift Studies rift zones.. Has zones.. Has done most done most of her work of her work in Ethiopia, in Ethiopia, East AfricaEast Africa

Rift photo by Ebinger in EthiopiaRift photo by Ebinger in Ethiopia

Plates move apart Plates move apart 8-12 cm/year 8-12 cm/year

Fingernails grow 6 Fingernails grow 6 cm/yearcm/year

Rift in IcelandRift in Iceland

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

Facts that support continental driftFacts that support continental drift

1. Similar 1. Similar shaped shaped continentscontinents

2. Similar fossils across Atlantic2. Similar fossils across Atlantic

3. Magnetic Reversals3. Magnetic Reversals

4.4. Sediment deepest at edges of Sediment deepest at edges of continents – thinnest at ridge (dust continents – thinnest at ridge (dust

settling on ocean surface)settling on ocean surface)

5.Youngest rocks are at the center 5.Youngest rocks are at the center and rocks at the edges of the and rocks at the edges of the

Atlantic are 150 million years oldAtlantic are 150 million years old

Active MarginActive Margin Plates Plates

running into running into each othereach other

Volcanoes, Volcanoes, mountain mountain building, building, earthquakesearthquakes

Subduction –one plate moves under Subduction –one plate moves under the otherthe other

Volcano 100 km from trench

South America is moving westSouth America is moving westcolliding with Nazca platecolliding with Nazca plate

Trench ↑ ↑ Mountains

Passive MarginPassive Margin

Growing platesGrowing plates

Volcanic Islands are found only Volcanic Islands are found only at ACTIVE plate boundariesat ACTIVE plate boundaries

Forms LITHOGENIC SEDIMENT- break up Forms LITHOGENIC SEDIMENT- break up of rocks (Quartz)of rocks (Quartz)

Andros Andros nono Quartz – Quartz –nono volcano volcano– Biogenic sedimentBiogenic sediment

Made of skeletons and shells of marine organismsMade of skeletons and shells of marine organisms

Why study plate tectonics?Why study plate tectonics?

What do you find at active boundaries?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 Active Plate Margin vs Passive Plate MarginPlate Margin

Active MarginActive Margin- little or no shelf (shelf is - little or no shelf (shelf is crushed by movement)crushed by movement)

therefore minimal amount of fishing (no shallow therefore minimal amount of fishing (no shallow water for plants), EXEPT at upwellingswater for plants), EXEPT at upwellings

Passive plate marginPassive plate margin- very wide shelf- very wide shelf Therefore (shallow water for plants) major fishing, Therefore (shallow water for plants) major fishing,

because of shallow waterbecause of shallow water

Shelf is only 8% of the ocean’s Shelf is only 8% of the ocean’s surface, but the most valuable.surface, but the most valuable.

Average width 40 milesAverage width 40 miles Average depth 197 feetAverage depth 197 feet Slope is undetectable to eye (flat because turbidity Slope is undetectable to eye (flat because turbidity

(Mud) currents from rivers level out the slope(Mud) currents from rivers level out the slope

Biologically riches part of Biologically riches part of the oceanthe ocean

Divisions of oceansDivisions of oceans Benthic –Benthic –

– Topography of the ocean bottomTopography of the ocean bottom Pelagic –Pelagic –

– Water environmentWater environment

Pelagic divisionsPelagic divisions

Photic – Photic – – Lighted areas Lighted areas

where where photosynthesis photosynthesis takes placetakes place

Aphotic –Aphotic –– Light does NOT Light does NOT

penetratepenetrate

Pelagic (water) environment Pelagic (water) environment divided by depthdivided by depth

NeriticNeritic – – water near water near the shorethe shore

OceanicOceanic——water water beyond the beyond the shelfshelf

Deep Deep OceanOcean – – ocean floorocean floor

Neritic (near shore)Neritic (near shore)

Large variety of conditionsLarge variety of conditions

Salinity changes caused by:Salinity changes caused by:EvaporationDilution from freshwater riversDilution from freshwater rivers

Temperature changes- water depthTemperature changes- water depthMOST BIOLOGICALLY MOST BIOLOGICALLY PRODUCTIVE PART OF THE SEAPRODUCTIVE PART OF THE SEA

Oceanic (beyond the shelf)Oceanic (beyond the shelf)

Conditions are more Conditions are more constantconstant

–Slow moving currentsSlow moving currents

–Temperature constant Temperature constant (except in thermoclines)(except in thermoclines)

Deep OceanDeep Ocean

Bathyal – edge of shelfBathyal – edge of shelfAbyssal – deep oceanAbyssal – deep oceanHadal – trenchesHadal – trenches

Environment of Deep OceanEnvironment of Deep Ocean High water pressure??High water pressure??

Food ??Food ??No light – no plants ??No light – no plants ??

Oxygen ??Oxygen ??No light – no plants ??No light – no plants ??

OO22 is brought down by cold water density currents is brought down by cold water density currents

–Organisms are primarily HOrganisms are primarily H22O, because water is O, because water is

not compressible like airnot compressible like air

Most of food falls from the surfaceMost of food falls from the surface

Sea level has risen twice in the Sea level has risen twice in the last 30,000 years.last 30,000 years.

Why has sea level changed????Why has sea level changed????

Glaciers change sea levelGlaciers change sea level