CONTINENTAL DRIFT

HOW MANY CONTINENTS ARE THERE? 7- North America, South America, Africa, Europe, Asia, Australia, Antarctica

HAVE THE CONTINENTS ALWAYS LOOKS LIKE THIS?

WERE THE CONTINENTS ALWAYS LOCATED IN THE SAME POSITION? watch?v=WaUk94AdXPA &feature=related

A CONTINENTAL PUZZLE

CONTINENTAL DRIFT Who? Alfred Wegener (German meteorologist) When? 1912 He noticed the puzzle-like fit of the continents

He proposed that the continents were joined together in the past, in a large land mass called Pangaea.

Over time, the continents drifted (moved) apart Wegener named his theory “Continental Drift”. Describe it

HE SUPPORTED HIS THEORY WITH FOUR PIECES OF EVIDENCE.

Matching fossils of animals on once connected land areas. 1. Animal Fossil Clues

2. PLANT FOSSIL CLUES Fossils of the plant Glossopteris are found in rocks in South Africa, India, Australia, South America, and Antarctica

3. Climate Clues Glacial evidence in Africa, South America, Australia Fossils found in Antarctic soil indicate that the now frigid continent was once lush with trees and ferns, and home to dinosaurs, amphibians, and later, marsupials.

4. Rock Clues - similarities and ages Mountains in South America and Antarctica are believed to have formed as part of the same mountain chain.

WEGENER’S THEORY MADE SENSE, BUT NO ONE WANTED TO ACCEPT IT UNTIL THEY KNEW HOW THE CONTINENTS MOVED.

YEARS LATER SOMEONE CAME UP WITH AN EXPLANATION OF HOW THE CONTINENTS MOVED

SEAFLOOR SPREADING Who? Harry Hess (A Princeton University scientist) When? 1960’s

USING NEW TECHNOLOGY, THEY LOOKED AT THE OCEAN FLOOR Hess and other scientists mapped the ocean floor using sonar They detected underwater mountain ranges

Further examination of the ocean floor with a submarine showed underwater volcanoes. A variety of life living near the warm vents of the volcanoes was found

Sampling the rocks near the volcanoes revealed that there was a pattern to their formation.

DESCRIBE SEAFLOOR SPREADING Magma in the mantle rises and pushes the plates apart, forming new oceanic crust.

SEAFLOOR SPREADING CAUSES CONTINENTAL DRIFT Now we could explain HOW the continents moved:

HE SUPPORTED HIS THEORY WITH TWO PIECES OF EVIDENCE.

1. ROCK AGES Youngest rocks are found at the mid-ocean ridges and they become increasingly older farther from the edges.

2. MAGNETIC CLUES Magnetic iron particles record the time of the rock formation. When the magnetic north pole switched places, iron in the rocks recorded this information =2789

A MAP OF THE OCEAN FLOOR PROVIDES EVEN MORE EVIDENCE

ICELAND SHOWS SEAFLOOR SPREADING ABOVE THE WATER, WHICH MAKES IT EASIER TO STUDY