Environmental Science Plate Tectonics Environmental Science

Plate Tectonics The Earth Inside Out The Theory of Continental Drift Bathymetry and Seafloor Mapping The Theory of Continental Drift Lab continental drift Seafloor Spreading Lab seafloor spreading Plate Tectonics Lab plate tectonics

Earth’s Internal Layers How do we classify the Earth’s internal layers? How is the lithosphere different from the crust?

Layers of the Earth

Composition, Density and Temp. Core: Nickel (Ni), Iron (Fe) and other heavy elements Inner core and outer core same temperature however massive pressure and density keeps inner core solid Mantle: mostly Silicon (Si) and Oxygen (O) Lower density than core Lower mantle is solid, upper mantle is “plasticy”

Lithosphere and Asthenosphere

Lithosphere and Asthenosphere Lithosphere = Crust and upper part of upper mantle Asthenosphere = lower part of upper mantle Lithosphere “floats” on asthenosphere

Rock Cycle What are the three types of rock? How does the rock cycle account for their formation?

Isostatic Equilibrium How does Archimedes Principle relate to the structure of the Earth? What is isostatic equilibrium? What links some earthquakes with isostatic equilibrium? Where do such earthquakes occur?

Archimedes Principle

Archimedes Principle

Isostatic Equilibrium

Isostasy The lithosphere floats on the asthenosphere The various portions of the Earth’s crust reach gravitational equilibrium Due to variations in thickness and density, some crustal blocks ride higher than others Isostasy explains the vertical distribution of Earth’s crust. George Bedell Airy proposed that the density of the crust is everywhere the same and the thickness of crustal material varies. Higher mountains are compensated by deeper roots. This explains the high elevations of most major mountain chains, such as the Himalayas. G H Pratt hypothesized that the density of the crust varies, allowing the base of the crust to be the same everywhere. Sections of crust with high mountains, therefore, would be less dense than sections of crust where there are lowlands. This applies to instances where density varies, such as the difference between continental and oceanic crust. Condition of gravitational equilibrium of all parts of the Earth’s crust. The crust is in isostatic equilibrium if, below a certain depth, the weight and thus pressure of rocks above is the same everywhere. The idea is that the lithosphere floats on the asthenosphere as a piece of wood floats on water. A thick piece of wood floats lower than a thin piece, and a denser piece of wood floats lower than a less dense piece. There are two theories of the mechanism of isostasy, the Airy hypothesis and the Pratt hypothesis, both of which have validity. In the Airy hypothesis crustal blocks have the same density but different thicknesses; like ice cubes floating in water, higher mountains have deeper roots. In the Pratt hypothesis, crustal blocks have different densities allowing the depth of crustal material to be the same. In practice, both mechanisms are at work.

Isostatic Rebound Isostatic Equilibrium is the balance between the weight of the lithosphere and the buoyant force of the asthenosphere Isostatic Rebound is when compensation occurs from an increase or decrease of lithospheric weight…causing earthquakes along weak areas called - faults

Onto the Festivities!!!

Alfred Wegner and Continental Drift What is Pangea and Panthalassa? What is the theory of continental drift? What evidence did Wegner use to support his theory? Why didn’t scientists support his theory? What further evidence could have strengthened his theory?

Pangea Panthalassa

Wegner’s Theory Pangea: big supercontinent Panthalassa – Ocean surrounding Pangea Wegner theorized that because the less dense continents floated on the more dense matle, Pangea broke apart into separate pieces. Theory of Continental Drift

The Evidence Pieces fit together like a puzzle

Fossil Distribution

Accepted Theory? I Think Not! Good evidence but no go for public acceptance. Possibly because Alfred was a meteorologist not a geologist To many gaps between continents He disappeared on an expedition in 1930 in Greenland Later on, plate tectonics theory described how the gaps between the continents were continental shelves

O.k. Let’s Check It Out Pangea Lab!!!! Oooooh Yeah Baby!