Without Plate Tectonics, Earth Might Not Support Life

The ingredients for life to exist on our planet are liquid water, oxygen, and … plate tectonics? 

What is plate tectonics?

Looking at a map of the world, the coastlines of certain continents appear to complement each other. If we could just nudge them a little closer, they look like they could lock together like puzzle pieces. This isn’t just a trick of the eye! Geologists now think that North America, Africa, South America, and Europe were once one continuous landmass or one big continent called Pangaea. 

Pangaea eventually split into pieces sometime around 230 million years ago. Those pieces spread out to form the continents we know today. Geophysicist Alfred Wegener first proposed this theory of continental drift in the early 1900s, but at the time his idea didn’t gain much traction—people thought it was too strange. After all, the ground beneath our feet is rock solid and steady, right?

Evidence began to grow to support the idea of continental drift. Fossils from the same plants and animals were found on both sides of Earth's oceans, suggesting that those distant coastlines were once connected. Similarly, the age and types of rock matched up. 

Then in the 1950s, geologists discovered the mid-Atlantic ridge, a mountain range that runs along the ocean floor. The ridge is the largest geological feature on the planet and has been classified as a World Heritage Site. Most of the ridge sits far below the depths of the ocean. But in a few spots—including Norway, the UK, and Brazil—the mountains pop up above the surface of the water to form island chains. 

When studying the seafloor around the ridge, geologists learned that the farther from the ridge they looked, the older the seafloor. In 1962, geologist Harry Hess proposed that this age differential arose due to seafloor spreading. At the ridge, rock was being forced up from the Earth’s interior forming new a seafloor, which effectively pushed the older layers out of the way. 

The theory of plate tectonics brings all of this evidence...

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