PLATE TECTONICS

LAYERS OF THE EARTH

LITHOSPHERE vs ASTHENSOPHERE LITHOSPHERE - crust together with a hard upper part of the mantle (PLATES, Crust under continents, crust under ocean ASTHENOSPHERE – (Below Lithosphere) So much pressure and heat the rocks can flow like a liquid. Allows Lithosphere to “float” on top of it. HOW TO REMEMBER: L.A. Lithosphere on outside, Asthenosphere on in the inside. L.A.

OUTER MOST LAYER THINNEST LAYER LAND, OCEAN FLOOR, PLATES CRUST OUTER MOST LAYER THINNEST LAYER LAND, OCEAN FLOOR, PLATES CONTINENTAL CRUST OCEANIC CRUST Under the Land Under the ocean THICK CRUST (20-40 miles thick) LOW DENSITY LIGHT COLOR GRANITE THIN CRUST (3 miles thick) HIGH DENSITY DARK COLOR BASALT

TAFFY LIKE (not solid, not liquid) LAYERS We used Seismic Data (from earth quakes etc) to develop our model for what the interior of the earth is made of. The deepest we have ever drilled doesn’t even reach the mantle MANTLE OUTER CORE INNER CORE TAFFY LIKE (not solid, not liquid) Thick Liquid Metal Solid Outer Mantle & Crust form Lithosphere Magnetic Field Dense Metal Inner Mantle forms Asthenosphere 8100 Degrees F Iron and Nickle 1800 Miles Thick 9000 Degrees F

LAYERS and CHARACTERISTICS Layers formed using differentiation: More dense (heavier) materials went to the center (CORE) Less dense (lighter) materials went to the crust (PLATES, ROCKS) ***Differences in DENSITY separate the earth’s layers

AS DEPTH INCREASES (closer to center of earth) As depth INCREASES, Temperature INCREASES As depth INCREASES, Pressure INCREASES As depth INCREASES, Density INCREASES TEMPERATURE INCREASES PRESSURE INCREASES DENSITY INCREASES

RAIO ACTIVE DECAY – Earth’s internal heat source Earth has been losing heat since it formed, billions of years ago. But it’s producing almost as much heat as it’s losing. The process by which Earth makes heat is called radioactive decay. It involves the disintegration of natural radioactive elements inside Earth – like uranium, for example. Uranium is a special kind of element because when it decays, heat is produced. It’s this heat that keeps Earth from cooling off completely.

Continental Drift Theory 1910 Alfred Wegener Hypothesis: all the continents had once been joined together in a single landmass PANGEA! Evidence: Land “fit” together like puzzle, Fossils, BUT…. He couldn’t explain how the continents actually moved apart. So they rejected him!

SEA-FLOOR SPREADING (helped explain continental drift) Occurs at mid-ocean ridges Ocean floors move like treads on a bulldozer or tank Lava rises from the mantle through the ridge. Lava then spreads out, pushing older rock to both sides of the ridge. Magma flows upward because it is LESS DENSE then the surrounding rock.

As distance from the mid-ocean ridge increases – The Age of the crust increases (further away the older… closer to the ridge the younger) Lava rises, then cools at the ridge. New lava rises and pushes the existing cooled lava away from the Ridge. This Repeats.

Why don’t the oceans continue to get wider and wider if the sea floor is spreading? Deep-ocean trenches form where oceanic crust bends downwards. SUBDUCTION: process where ocean floor sinks beneath a deep- ocean trench and back into the mantle. CONVECTION drives sea floor spreading.

THEORY OF PLATE TECTONICS Lithosphere is broken up into separate sections called PLATES. Plates carry the continents or part of the ocean floor. Theory of Plate Tectonics states that pieces of the earth’s lithosphere are in constant, slow motion, DRIVEN BY CONVECTION CURRENTS in the mantle. Plates of Lithosphere float on top of the asthenosphere. Convection currents rise in the asthenosphere and spread out beneath the lithosphere. Causes plates to move. If one plate moves, it makes another move. As plates move, they collide, pull apart, or grind past each other…..producing Mountains, volcanoes, and Deep Sea Trenches.

PLATES (*Pacific plate and North American Plate

EVIDENCE OF PLATE TECTONIC MOVEMENT Matching up rock layers over wide distances Matching up fossils, and plants over wide distances Noticing forces that happen today and knowing they happened in the past. (Subduction, Convection, Faulting) (Uniformitarianism)

DIVERGENT BOUNDARY Two plates move apart (divide) Mid Ocean Ridge is Divergent Boundary If divergent boundary is on land, Rift Valley forms.

Rift Valley Kenya (divergent)

CONVERGENT BOUNDARY Two plates move towards each other (Converge) Himalaya Mountains are Convergent boundary

Himalayan Mountains (cont – cont convergent)

TRANSFORM BOUNDARY Two plates slip past each other moving in opposite directions SAN ANDREAS FAULT is transform boundary (Pacific plate & North Amer. Plate

San Andreas Fault ( Transform boundary)