Radiometric dating online activity

It explains tectonic activity (things like earthquakes and the building of mountain ranges) at the edges of continental landmasses (for instance, the San Andreas Fault in California and the Andes in South America).

At 50 years old, with a surge of interest in where the surface of our planet has been and where it’s going, scientists are reassessing what plate tectonics does a good job of explaining – and puzzling over where new findings might fit in.

View the full list Fifty years ago, there was a seismic shift away from the longstanding belief that Earth’s continents were permanently stationary. Tuzo Wilson published Did the Atlantic Close and then Re-Open? The Canadian author introduced to the mainstream the idea that continents and oceans are in continuous motion over our planet’s surface.

Known as plate tectonics, the theory describes the large-scale motion of the outer layer of the Earth.

A map of ancient continental collisions may represent regions of hidden tectonic activity.

These old impressions below the Earth’s crust may still govern surface processes – despite being so far beneath the surface.

Regions where anomalous scarring beneath the crust are marked by yellow crosses.

Based on radiometric dating of rocks, we know that no ocean is more than 200 million years old, though our continents are much older.

The oceans’ opening and closing process – called the Wilson cycle – explains how the Earth’s surface evolves.

Together, they’re called the lithosphere and make up the “plates” in plate tectonics.

We now know there are 15 major plates that cover the planet’s surface, moving at around the speed at which our fingernails grow.

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