Drifting Continents

Queen Elizabeth Islands Greenland Japan Iceland Malasia Madagascar New Zealand

Early Observers In the late 1500s, A Dutch mapmaker noticed that the continents fit together like a puzzle on either side of the Atlantic Ocean. Abraham Ortelius proposed that North and South America had been separated from Europe by earthquakes and floods.

Early Observers Then, a man named Eduard Suess hypothesized that the present southern continents had once been joined together in a landmass called Gondwanaland.

Alfred Wegener In 1912, created his hypothesis called “continental drift.” Continental drift = hypothesis that the Earth’s continents had once been joined as a single landmass.

The Supercontinent Pangaea = the supercontinent that means “all the earth” in Greek. Wegener thought that Pangaea began to break apart about 200 million years ago.

Continental Drift

Alfred Wegener So, no one believed him because he did not explain… What force could be strong enough to move such large masses of rock over such great distances? How are the continents moving? What is the evidence?

Evidence Geologic Fossils Climatic

Rock Formation Evidence Wegener hypothesized that there should be areas of similar rock types on opposite sides of the Atlantic Ocean. Rocks of the Appalachian Mountains shared features with rocks in Europe. These rocks were over 200 million years old.

Matching Mountain Ranges

Geologic features seem to fit together…

Evidence from Fossils Similar fossils of several different animals and plants that once lived on land had been found across many different continents Animals that were found on separated continents included animals that could have never swum across oceans!

Fossil Evidence

Climatic Evidence Wegener found climatic evidence such as glacial deposits. Glacial deposits were found in Africa, India, Australia and South America. Today the climate is much too hot to support glaciers .

Glacial Evidence in South Africa The Dwyka Tillite shown above formed from sediment dropped from icebergs.  The boulder being pointed to is a dropstone left by a melting iceberg.  The Dwyka Tillite correlates with similar rocks in South America, India, Australia, and Antarctica.  Alfred Wegener considered this tillite to be evidence of continental drift.

REJECTED!!! Despite all of the evidence most people did not believe Alfred Wegener because he did not explain what was causing the continents to move and how they were moving.

Seafloor spreading An American Scientist named Harry Hess proposed the theory called sea floor spreading. Sea floor spreading: states that new ocean floor is formed when tectonic plates move

Seafloor renewal Magma is hot and rises upward along an ocean ridge and fills in the gap like a scab. When the magma hardens, you get a small amount of new ocean floor.