MOVEMENT OF PLATES CONVECTION CURRENTS EVIDENCE FOR Why

MOVEMENT OF PLATES

CONVECTION CURRENTS

EVIDENCE FOR Why don’t believe CONTINENTAL people DRIFT me? ? ? Must be the hat. • ALFRED WEGENER--GERMAN • THEORY OF CONTINENTAL DRIFT • EARLY 1900’S

CONTINENTAL DRIFT • IDEA PROPOSED BY WEGENER THAT ALL CONTINENTS HAD ONCE BEEN JOINED TOGETHER AND HAVE “DRIFTED” TO THEIR PRESENT POSITIONS • IT LOOKS SOMETHING LIKE THIS:

PANGAEA

EVIDENCE!!!!! • FIT OF THE CONTINENTS SOUTH AMERICA AFRICA

MIGHTY MESOSAURUS

THE MAIN EVENT • MESOSAURUS VS. • TRUCKOSAURUS

EARTHQUAKES & VOLCANOES

RING OF FIRE

MORE EVIDENCE…. .

The Earth is a dried apple…? ? • Many scientists of the day believed that mountains formed due to the earth slowly cooling and shrinking (like what a dried apple does) What you talking about Willis? ?

Wegener Rejects! You. Tube - Lebron James Rejects Yao Ming • If that theory were • When continents true, mountains would collide, their edges be found all over the crumple and fold planet • Ex. The Appalachian • Wegener proposed that mountains are mountains only nicknamed “the occurred in narrow folded” mountians bands along the edges of continents

UNFORTUNATELY…… • NOBODY BELIEVED WEGENER TILL HA HA!! THE LATE 1960’S What was the main reason that scientists did not believe Wegener’s theory? ?

That’s right……. • He couldn’t prove HOW the continents moved (convection currents) • It wasn’t until the 1950’s and 1960’s that we discovered sea-floor spreading centers at the bottom of the ocean

TRAGEDIES of CONTINENTAL DRIFT

Sea-floor Spreading • Harry Hess –American geologist • Studied mid-ocean ridges using SONAR • Developed idea that new sea-floor is created along a crack in the ocean floor

Evidence for Sea-floor spreading • Eruptions of molten material • Magnetic stripes in the ocean floor • Ages of rock (oldest rock is furthest away from the spreading center) See Mr. Fett’s Model

Evidence from Drilling Samples • Glomar Challenger—Drilling ship (1968) • Collected rock samples through pipes 6 km deep • Scientists found that the farther away from a ridge the samples were taken, the older the rocks were

Subduction at Trenches • Ocean floor plunges into deep water canyons called trenches • Part of the ocean floor sinks back into the mantle—this is called subduction

Marianas Trench Aprox 7 miles deep

Sea-floor Spreading in Review

PLATE TECTONICS

Based on Yesterday’s class… use a piece of notebook paper…this will be a page in your notebook • Name three pieces of evidence that Wegener used to help promote his theory of continental drift. • Why was his theory ultimately rejected by the scientific community? • What discovery in the 1960’s helped bring his theory back to life?

TECTONIC PLATES

DIVERGENT BOUNDARY MID-OCEAN RIDGE

MAGNETIC REVERSALS

NORTHWEST VOLCANOES

THE GEOLOGIC RECORD Law of Superposition states that in an undisturbed sequence of sedimentary rocks, the oldest rocks will be at the bottom and the youngest will be at the top. • Law of cross-cutting relationships– an igneous rock is younger than the rocks it has intruded or cut across. (can also be applied to fault surfaces)