Continental drift is a theory that explains how continents change position on Earth's surface. The theory was rejected by mainstream science at the time it was proposed. Some of Wegener's ideas were confirmed by scientists decades later.
The idea of moving continents to geoscience was introduced by Wegener's continental drift theory. He proposed that Earth was once a single supercontinent before it broke up. Similar rock formations and plant and animal fossils could be found on different continents. Wegener theorizes that Pangaea existed before it broke up about 200 million years ago.
A huge supercontinent will form hundreds of millions of years from now.
Why did scientists reject the continental drift theory?
Wegener's continental drift theory was denounced by geologists after he published details in a 1915 book. Scientists later explained that Wegener didn't have a good model to explain how the continents moved because they didn't have a rock layer called the mantle.
The main objection to continent drift was that there was no mechanism to move the continents.
Most of Wegener's observations about fossils and rocks were correct, but he was wrong on a couple of key points. Wegener thought the continents might have smashed through the ocean crust like icebreakers.
Evolving theories.
Many geologists were contractionists when Wegener proposed continental drift. They thought the mountains were created because the planet had been cooling. Scientists used ancient land bridges to account for the same fossils found on the same continents.
The plate tectonics theory was developed in the 1950s to the 1970s, and researchers argued over the land bridges right up until then. When it was realized that continental rocks were too light to sink to the ocean floor, prominent paleontologists wrongly suggested that the similarities between fossils had been overstated.
Modern plate tectonics is an update to continental drift. Scientists discovered plate edges through magnetic surveys of the ocean floor and through the seismic listening networks built to monitor nuclear testing in the 1960s. There were alternating patterns of magnetic anomalies on the ocean floor. The continents have shifted relative to one another, as shown by the magnetic minerals aligned in ancient rocks.
The oldest minerals on Earth are from 3.6 billion years ago.
There is evidence for continental drift.
The plates of the Earth.
Wegener was inspired by a map of the continents. The fit of Africa's and South America's shorelines caught his attention. Wegener's evidence shows that the continents were once connected in a single supercontinent.
Wegener knew that fossils of mesosaurs, a freshwater reptile found only in South America and Africa during the Permian period, could be found on many continents. On either side of the Atlantic Ocean, he matched up rock formations like puzzle pieces. The Appalachian Mountains in the United States and the Caledonian Mountains in Scotland fit together, as do the South Africa and Santa Catarina rocks.
The highest mountains in the world, the Himalayans, and the mountains are still growing because of the plates pushing together, according to National Geographic. Wegener's theory never gained wider acceptance despite his incredible continental drift evidence. He died two days after his 50th birthday while on a scientific expedition in Greenland, according to the University of Berkeley.
There are additional resources.
Live Science Staff Writer Patrick Pester updated the article on December 14, 2021. Additional reporting by a Live Science contributor.
