Continental drift

Abraham Ortelius by Peter Paul Rubens

Antonio Snider-Pellegrini Opening of the Atlantic

Alfred Wegener 1910

Snider-Pellegrini Wegener fossil map

Mesosaurus

Continental drift is the theory that the Earth's continents have moved over geologic time relative to each other, thus appearing to have "drifted" across the ocean bed. The concept was initially proposed by Abraham Ortelius in 1596, but it was not until the work of Alfred Wegener in the early 20th century that the idea gained widespread acceptance among scientists. Wegener's hypothesis of continental drift was later replaced by the theory of plate tectonics, which provided a more comprehensive explanation of the movement of the Earth's plates and the mechanisms driving them.

History

The idea of continental drift was first put forward by Ortelius when he noticed the complementary coastlines of the Atlantic Ocean's continents, suggesting that they were once joined together. However, it was Alfred Wegener who, in 1912, proposed the theory of continental drift with substantial evidence. Wegener suggested that a single supercontinent, which he named Pangaea, existed around 300 million years ago before it began to break apart into the continents we know today. His evidence included the fit of the continents, the distribution of fossils, and the similarity of rock formations on different continents.

Despite the compelling evidence presented by Wegener, his theory was initially met with skepticism from the scientific community. This was largely due to the lack of a plausible mechanism for the movement of continents. It wasn't until the development of the theory of plate tectonics in the 1960s, which described the Earth's lithosphere as divided into tectonic plates that move over the asthenosphere, that Wegener's idea of continental drift was widely accepted.

Mechanism

The mechanism behind continental drift and plate tectonics involves the movement of the Earth's lithosphere, which is divided into several large and some smaller plates. These plates move relative to each other at rates of a few centimeters per year, driven by forces such as mantle convection, slab pull, and ridge push. The interactions between these plates can lead to the formation of mountains, earthquakes, and volcanoes, as well as the creation and destruction of oceanic crust.

Evidence

Evidence for continental drift and plate tectonics is extensive and includes geological, paleontological, and geophysical data. Geological evidence includes the jigsaw-puzzle fit of the continents, particularly the east coast of South America and the west coast of Africa. Paleontological evidence involves the distribution of fossils across continents that are now widely separated by oceans, suggesting these continents were once connected. Geophysical evidence includes the pattern of magnetic stripes on the ocean floor, which records reversals of the Earth's magnetic field and the spreading of the seafloor.

Impact

The acceptance of continental drift and plate tectonics has had a profound impact on the earth sciences, leading to a unified framework for understanding geological processes. It has also had implications for other fields, such as paleoclimatology and evolutionary biology, by providing explanations for the distribution of climates and species over time.

See Also

• Plate tectonics
• Pangaea
• Alfred Wegener
• Earth's lithosphere
• Mantle convection