Listen to Episode 122 on PodBean, YouTube, Spotify, or wherever you feel like it!
The Earth is in motion beneath our feet, and this motion impacts nearly every feature and activity on the planet’s surface. And yet, we’ve only recently come to understand this central geological phenomenon. This episode, we discuss the scientific history and the deep history of Plate Tectonics.
In the news
“Petal-toothed” sharks discovered in China
Newly discovered, unusually large Cambrian predator
At long last, a description of Carnotaurus skin
Teratorn birds survived longer than expected in South America
A Foundational Theory
Plate tectonics isn’t just any scientific theory, it’s a major unifying theory. Nearly every feature of the Earth’s surface – continents, oceans, trenches, mountains, earthquakes, volcanoes, etc. – are linked by the complex motions of the tectonic plates. And yet, this is a relatively recent revelation for the scientific community.
The Earth’s lithosphere (that is, the crust and uppermost mantle) is not a single solid shell. It’s broken into pieces like a cracked egg. These pieces – plates – are constantly in motion, shifting slowly like gargantuan conveyor belts. As these giant chunks of crust slide together, apart, and past each other, oceans open and close, continents rift and collide, and all that tectonic activity generates a world’s worth of earthquakes and volcanoes.
The motion of the plates is so slow (typically a few centimeters per year) that it’s no surprise it took scientists a while to realize they moved at all. German scientist Alfred Wegener popularized the idea of Continental Drift in the early 1900s – he noticed the matching shape and geology of shorelines on opposite sides of the Atlantic Ocean and suggested the continents were once joined together. But it took several decades and a lot more evidence before the theory of Plate Tectonics as we know it came to be accepted.
Tectonics in Time
For billions of years, the motion of the plates has slowly shaped Earth’s surface. As we peer into the past, we can follow geologic evidence to reconstruct the planet’s surface as it once looked. Today’s continents feature huge mountains, the sites of previous continental collisions; vast oceans, which began as rifts that tore continents apart; and coastlines that share fossils, mountain ranges, and geologic layers despite being separated by oceans today. Certain rocks and minerals in ancient sediments can identify subduction zones and rift zones of the past, and magnetic signatures in ancient rocks can reveal if a continent used to be nearer or farther from the North or South pole.
Plate tectonics is a big deal for paleontology, since life has always reacted to the shifting surface. As continents separate and conjoin, as oceans open and close, plants and animals gain or lose opportunities for dispersing around the globe. Mountains and trenches can form impassable barriers or exploitable habitats, while the island chains formed above subduction zones or hot spots can be crucibles for evolutionary diversity. And, of course, the shapes of oceans and continents can impact water and air currents, and thus the climates of the past.
This Dynamic Earth: the Story of Plate Tectonics – learn lots more details with this USGS module
Plates on the Move – educational tectonics game from the AMNH
Paleolatitude calculator – find your own paleolatitude!
Bradley 2011. Secular trends in the geologic record and the supercontinent cycle. A detailed overview of how we reconstruct continental movement in the past (technical)
Explore some of the big questions about plate tectonics:
When and how did plate tectonics begin on Earth?
Does plate tectonics exist elsewhere in the universe? Investigations of Mars, Venus, Europa, Titan, and exoplanets.
If you enjoyed this topic and want more like it, check out these related episodes:
- Episode 141 – Supercontinents
- Episode 131 – Volcanoes
- Episode 45 – The Permian Extinction
- Episode 12 – The Geologic Time Scale
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