What makes continental drift

Continental drift describes one of the earliest ways geologists thought continents moved over time. Today, the theory of continental drift has been replaced by the science of plate tectonics. The theory of plate tectonics revolutionized the earth sciences by explaining how the movement of geologic plates causes mountain building, volcanoes, and earthquakes. In , after decades of tediously collecting and mapping ocean sonar data, scientists began to see a fairly accurate picture of the seafloor emerge.

The Tharp-Heezen map illustrated the geological features that characterize the seafloor and became a crucial factor in the acceptance of the theories of plate tectonics and continental drift. Today, these theories serve as the foundation upon which we understand the geologic processes that shape the Earth.

Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image Alfred Wegener in Greenland Plate tectonics is the theory that Earth's land masses are in constant motion. Photograph from Pictoral Press. Twitter Facebook Pinterest Google Classroom.

Article Vocabulary. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. Media If a media asset is downloadable, a download button appears in the corner of the media viewer. Text Text on this page is printable and can be used according to our Terms of Service. There are three possible explanations for this: 1 The continents remained fixed and the north magnetic pole moved.

Geologists noted that for rocks of the same age but on different continents, the little magnets pointed to different magnetic north poles. For example, million-year-old magnetite in Europe pointed to a different north magnetic pole than the same-aged magnetite in North America. Around million years ago, the north poles were also different for the two continents.

The scientists looked again at the three possible explanations. Only one can be correct. If the continents had remained fixed while the north magnetic pole moved, there must have been two separate north poles. Since there is only one north pole today, the only reasonable explanation is that the north magnetic pole has remained fixed but that the continents have moved.

To test this, geologists fitted the continents together as Wegener had done and behold, it worked. There has only been one magnetic north pole and the continents have drifted. They named the phenomenon of the magnetic pole that seemed to move but actually did not apparent polar wander. Licenses and Attributions. Plate tectonics is now the widely accepted theory that Earth's crust is fractured into rigid, moving plates.

In the s, scientists discovered the plate edges through magnetic surveys of the ocean floor and through the seismic listening networks built to monitor nuclear testing, according to Encyclopedia Britannica. Alternating patterns of magnetic anomalies on the ocean floor indicated seafloor spreading , where new plate material is born.

Magnetic minerals aligned in ancient rocks on continents also showed that the continents have shifted relative to one another. A map of the continents inspired Wegener's quest to explain Earth's geologic history. Trained as a meteorologist, he was intrigued by the interlocking fit of Africa's and South America's shorelines. Wegener then assembled an impressive amount of evidence to show that Earth's continents were once connected in a single supercontinent.

As the seafloor grows wider, the continents on opposite sides of the ridge move away from each other. The two continents are moving away from each other at the rate of about 2.

Rift valley s are sites where a continental landmass is ripping itself apart. Africa, for example, will eventually split along the Great Rift Valley system. What is now a single continent will emerge as two—one on the African plate and the other on the smaller Somali plate.

The new Somali continent will be mostly oceanic, with the Horn of Africa and Madagascar its largest landmasses. The processes of seafloor spreading, rift valley formation, and subduction where heavier tectonic plates sink beneath lighter ones were not well-established until the s.

These processes were the main geologic forces behind what Wegener recognized as continental drift. The way some continents fit together like puzzle pieces inspired the theory of continental drift. Map by USGS. Alfred Wegener. Great Rift Valley system. Mid-Atlantic Ridge. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

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Interactives Any interactives on this page can only be played while you are visiting our website. Related Resources. Plate Tectonics.