1 minute read

Continental Drift

Evidence Of The Theory

Technological improvements after World War II supported many of Wegener's ideas about continental drift. New methods of dating and drilling for rock samples, especially from deep-sea drilling ships like the Glomar Challenger, have allowed more precise matching of Pangaea's rocks and fossils. Data from magnetometers (instruments that measure the magnetism of the iron in sea floor rocks) proved that the sea floors have spread since Pangaea's breakup. Even satellites have clocked continental movement.

Geologists assume that, for the 100 million years that Pangaea existed, the climatic zones were the same as those operating today: cold at the poles, temperate to desert-like at the mid-latitudes, and tropical at the equator. The rocks and fossils deposited in the early days of Pangaea show that the equator crossed a clockwise-tilted North America from roughly southern California through the mid-Atlantic United States and into Northwestern Africa. Geological and archaeological evidence from the Sahara desert indicate the remains of a tropical world beneath the sands. Rock layers in southern Utah point to a warm sea that gradually altered into a large sandy desert as the west coast of the North American section of Pangaea slid north into a more arid latitude. Global climates changed as Pangaea rotated and slowly broke up over those 100 million years.

Meanwhile, dinosaurs, mammals, and other organisms evolved as they mingled across the connected Earth for millions of years, responding to the changing climates created by the shifting landmass. Fossil dinosaurs unearthed in Antarctica proved that it was connected to the rest of Pangaea, and dinosaur discoveries in the Sahara desert indicate that the last connection between Laurasia (the northern half of Pangaea) and Gondwana was severed as recently as 130 million years ago.

All these discoveries also helped to develop the companion theory of plate tectonics, in which moving plates (sections of Earth's outer shell or crust) constantly smash into, split from, and grind past each other. Wegener's theory of Continental Drift predated the theory of plate tectonics. He dealt only with drifting continents, not knowing that the ocean floor drifts as well. Parts of his Continental Drift theory proved wrong, such as his argument that continental movement would cause the average height of land to rise, and parts proved correct. The Continental Drift theory and plate tectonics, although demonstrating many interrelated ideas, are not synonymous.

Additional topics

Science EncyclopediaScience & Philosophy: Condensation to CoshContinental Drift - History Of Wegener's Theory, Evidence Of The Theory, Formation Of Pangaea, Pangaea Splits