Discoveries Which Led up to the Theory of Plate Tectonics

Ancient Climate

May 12, 1915

Wegener found glacial deposits that showed that 220-300 million years ago sheets of ice covered much of the Southern Hemishpere in areas that now have temperate or tropical climates.

Similar Mountain Ranges

Aug 14, 1915

Mountain ranges were found to have been made of the same material even though they are seperated by oceans.

Matching Fossils

Oct 11, 1915

Identical fossils were found in different continents in places that could have been previously connected.

Hypothesis of Continental Drift

Dec 31, 1915

Alfred Weneger develops the hypothesis of Continental Drift.

Material of Ocean Floor

Oct 11, 1955

Scientists find that the basalt on the ocean floor alternates with it's polarity as a result of Sea-Floor Spreading.

Hypothesis of Sea-Floor Spreading

Nov 5, 1963

Harry Hess comes up with the hypothesis of Sea-Floor Spreading.

Earthquakes

Oct 11, 1975

Kiyoo Wadati and Hugo Benioff found that the deeper the earthquakes occur, the farther they were from the deep-ocean trenches, which told them that the slabs of ocean floor returned to the mantle after subducting.