In a new study, scientists suggest that the disintegration of supercontinents may have triggered explosive eruptions that hurled diamond fountains to Earth’s surface. The post writes about it Nature.

“As you know, diamonds are formed deep in the earth’s crust, at a depth of about 150 kilometers. They come to the surface very quickly as a result of explosions called kimberlites. Thomas Gernon, professor of Earth and climate science at the University of Southampton (England), said, “These kimberlites are between 18 and 133 km/h. “It moves at velocities and some eruptions may have caused Vesuvius-like explosions of gas and dust,” he said.

According to Gernon, researchers noticed that kimberlites were most likely formed during periods of significant realignment of tectonic plates, for example, during the disintegration of the supercontinent Pangea. Strangely, however, kimberlites often erupt in the middle of continents rather than at the edges of rifts – and this inner crust is thick, hard and difficult to crack.

“Diamonds have been on the floor of continents for hundreds of millions or even billions of years,” Gernon said. “There must be some kind of stimulus that suddenly detonates them, because those explosions themselves are really powerful, really explosive.”

Gernon and colleagues began by looking for a relationship between the age of kimberlites and the degree of plate fragmentation that was occurring at the time. They found that there was a pattern in which the plates began to separate from each other in the last 500 million years, followed by the kimberlite eruption peaking 22-30 million years later. (This pattern has also been going on for the past 1 billion years, but with greater uncertainty given the difficulty of tracing geological cycles that go back that far.)

For example, the researchers found that kimberlite eruptions began about 180 million years ago in what is now Africa and South America, about 25 million years after the southern supercontinent Gondwana broke up. Modern North America saw an increase in kimberlites after Pangea began to break apart about 250 million years ago. Interestingly, these eruptions of kimberlite seemed to start at the edges of the crevices and then continuously move towards the center of the terrain.

To find out what causes these patterns, the researchers used various computer models of the deep crust and upper mantle. They found that as the tectonic plates split apart, the bottom of the continental crust thinned—just as the upper crust stretched out and formed valleys. The hot rock rises, comes into contact with this now deteriorated boundary, cools and descends again, forming local circulation zones.

These unstable regions can cause instability in neighboring regions and slowly move thousands of miles towards the center of the continent. The discovery is reportedly consistent with the true kimberlite eruption pattern that started near the rift zones and then moved towards the interior continents.

But how do these imbalances trigger explosive eruptions from deep within the crust? “It’s all about mixing the right ingredients,” Gernon said. The instability is enough for rocks from the upper mantle and lower crust to flow toward each other.

This knocks down the rock with large amounts of water and carbon dioxide trapped within it, as well as many important kimberlite minerals, including diamonds. According to Gernon, the result is like shaking a bottle of champagne: explosions with great explosive potential and buoyancy to bring them to the surface.

According to Gernon, the data could be useful in searching for undiscovered diamond deposits. They may also help explain why other types of volcanic eruptions sometimes occur long after a supercontinent breaks up in areas that should be largely stable.

“It’s a fundamental and highly organized physical process,” Gernon said, “so it’s probably not just kimberlites that are responding to it, but all Earth system processes that are responding to it.” Source