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Kīlauea Iki in Hawaii is one place geologists have found volcanic rock that contains evidence of what Earth was like 4.5 billion years ago. Pixabay, public domain

Rocks recently shot out of volcanoes contain evidence of what Earth was like when it was still a young planet, 4.5 billion years ago.

Geologists got a nice surprise when they discovered the composition of the volcanic rocks, because many believe the way material circulates within Earth’s solid mantle would erase that evidence over time, according to a report from the University of Maryland. But scientists from that university, who were leading a study into the rock, found leftover traces of our planet’s youth.

A study in the journal Science specifically identifies the tungsten and helium found in the samples — which came out of volcanoes in Hawaii, Samoa and Iceland — as “signatures of primordial material.” The specific variants of those two elements and the amounts in which they were found, researchers say, date back to the first 60 million years of the solar system’s life.

Read: Watch Some Hot Tungsten Destroy These Oreos (R.I.P. Cookies)

Tungsten is a metal that is known for its strength and hardness, as well as being highly dense and having a high melting point. Helium, on the other hand, is a low-density gas and one of the most abundant elements in our universe.

“The researchers are not yet sure how Earth’s mantle preserved these anomalies,” the university said. “But the group’s results suggest that some of these rocks contain material that survived through all of Earth’s history — and that the planet’s interior may not be well-mixed after all.”

According to the authors, one possible explanation for the ancient finding is that the volcanoes are erupting material from Earth’s core in order to bring these rare types of rocks to the surface.

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