C H. 3 LESSON 3.2 CONTINENTS CHANGE POSITION OVER TIME ALFRED WEGENER: THE FATHER OF PANGAEA & CONTINENTAL DRIFT

CONTINENTS JOIN TOGETHER & SPLIT APART

WEGENER’S HYPOTHESIS EARTH’S CONTINENTS WERE ONCE JOINED IN A SINGLE LANDMASS AND GRADUALLY DRIFTED APART. FOR MANY YEARS PEOPLE DID NOT ACCEPT WEGENER’S HYPOTHESIS. THEY THOUGHT IT WAS RIDICULOUS.

WEGENER’S THOUGHTS WEGENER BECAME ANGRY BECAUSE HIS THEORY WAS NOT TAKEN SERIOUS BY THE SCIENCE COMMUNITY. SO, HE SET OUT TO PROVE HIS THEORY OF CONTINENTAL DRIFT.

WEGENER’S EVIDENCE FOSSILS - WEGENER FOUND THE FOSSILS OF AN ANCIENT REPTILE, MESOSAURUS, IN WESTERN AFRICA. THIS WAS UNUSUAL BECAUSE THE REPTILE NORMALLY WAS NATIVE TO SOUTH AMERICA. IT DID NOT HAVE WINGS, AND IT COULD NOT SWIM IN SALT WATER. SO HOW DID IT GET TO WESTERN AFRICA? CLIMATE – WEGENER ALSO FOUND TROPICAL PLANT FOSSILS THE ROCKS OF GREENLAND. GREENLAND TODAY LIES NEAR THE ARTIC CIRCLE. HE ALSO FOUND THE ROCKS IN SOUTH AFRICA HAD SCRATCHES THAT ON GLACIERS COULD CAUSE!

EVIDENCE CONTINUED GEOLOGY – WEGENER SAVED THE BEST FOR LAST. HE SHOWED THAT THE TYPE OF ROCKS FOUND IN BRAZIL MATCHED THE ROCKS IN WESTERN AFRICA. ALSO, THE ROCKS IN NORTH AMERICA MATCHED THE ROCKS IN EUROPE NEAR THE SCOTLAND HIGHLANDS.

VIDEO CLIP #1 DISCOVERY

NOT SO FAST, MR. WEGENER WHAT CAUSED THEM TO MOVE APART?

WEGENER DIED STILL TRYING PROVE HIS THEORY OF PANGAEA AND CONTINENTAL DRIFT. WEGENER KNEW PANGAEA BEGAN TO SPLIT APART ABOUT 200 MILLION YEARS AGO. HE JUST DIDN’T KNOW WHAT CAUSED IT TO SPLIT.

THE THEORY OF PLATE TECTONICS EXPLAINS HOW PLATES AND THE CONTINENTS MOVE. A GROUP OF SCIENTIST IN THE MID 1900’S LATER WOULD HELP PROVE WHY OUR CONTINENTS MOVED AND ARE STILL MOVING TODAY!

EVIDENCE FROM THE SEA FLOOR SEA FLOOR SPREADING-THEY LEARNED THAT RIDGES FROM ALONG CRACKS IN THE CRUST ON THE SEA FLOOR. MOLTEN ROCK RISES THROUGH THE CRACKS, COOLS, AND FORMS NEW OCEANIC CRUST. THE OLD CRUST IS PULLED AWAY. AGE OF THE SEA FLOOR- YOUNG ROCK IS CLOSEST TO THE RIDGE, WHILE THE OLDER ROCK IS FARTHEST AWAY. THEY FOUND THIS BY DRILLING INTO THE CRUST. OCEAN TRENCHES – AT THESE SITES, OCEANIC CRUST

CONTINUED IS SINKING INTO THE ASTHENOSPHERE. OLD CRUST IS BEING DESTROYED AS NEW CRUST IS BEING FORMED. THEREFORE, THE EARTH REMAINS THE SAME SIZE.

CAUSES OF PLATE MOVEMENT RIDGE PUSH –MATERIAL FROM THE MID-OCEAN RIDGES PUSHES THE PLATES. SLAB PULL- GRAVITY PULLS COOLER, DENSER PLATES INTO THE ASTHENOSPHERE. CONVECTION CURRENTS – IN THE ASTHENOSPHERE, HEATED ROCK CONSTANTLY RISES, COOLS, SINKS, AND GETS HEATED AGAIN.

VIDEO CLIP # 2 DISCOVERY STREAMING