New basalt just dropped. An international team of scientists drilled nearly a mile into the Pacific seafloor and extracted a variety of the volcanic stone chemically and mineralogically different from any previously known sort.
The team examined a 49-million-year-old outcrop of stone that formed just a couple million years after the Ring of Fire, that famous half-moon of volcanic activity that lines the Pacific Rim. For the first few million years following its ignition, the ring burbled with a superheated intensity the team says formed a unique type of stone.
They hauled up this evidence of Earth’s history from nearly 8 km below the ocean’s surface. Their analysis suggests the fires that forged the rock were hotter and more expansive than previously thought. Their results were published last week in Nature Communications.
“The rocks that we recovered are distinctly different to rocks of this type that we already know about,” said co-author Ivan Savov, a geochemist and volcanologist at the University of Leeds, in a university press release. “In fact, they may be as different to Earth’s known ocean floor basalts as Earth’s basalts are to the Moon’s basalts.”
Basalt is a very common type of igneous rock that emerges from cooled lava flows, including from currently active volcanoes. But the pressures and temperatures from which the stones emerge completely change their characteristics. The stone, the team reports, probably formed toward the end of the volatile beginnings of the Ring of Fire. It’s previously gone undetected due to its extremely remote (and difficult to access) location.
Though ancient, the Ring of Fire is young in terms of Earth’s tectonic history. Some volcanic rock dates back billions of years, much older than the new rock’s 49 million years of existence.
The team drilled the sample using the JOIDES Resolution, a drilling rig capable of pulling samples from 10 km below the surface. (Not quite at a 8 km depth, the newly reported basalt wasn’t even pushing the rig’s limits.) Under a microscope, a cross-section of the stone looks like a freeze-frame from a kaleidoscope, a conglomeration of slate grays and sea greens. It comes from the Amami Sankaku Basin, some 966 km off the coast of Japan. Savov said that knowing the conditions that formed this basalt will help Earth scientists better understand the development of the larger formation from which it was drawn.
“In an era when we rightly admire discoveries made through space exploration, our findings show there are still many discoveries still to make on our own planet,” Savov said in the university release.
Rocks can tell us a lot about the history of the planet. Just recently, scientists examining rocks in Greenland uncovered evidence of a magma ocean that existed when Earth was just a baby, not long after the formation of the Moon.