New basalt has just fallen. An international team of scientists drilled nearly a mile into the Pacific ocean floor, extracting a variety of volcanic rock chemically and mineralogically unlike any previously known species.
The team examined a 49-million-year-old rock that originated just a few million years after the Ring of Fire, that famous crescent of volcanic activity along the Pacific Rim. For the first few million years after ignition, the ring rippled with an overheated intensity, forming a unique kind of stone, according to the team.
They retrieved this evidence of Earth’s history from nearly 5 miles below the ocean surface. Their analysis suggests that the fires that forged the rock were hotter and more extensive than previously thought. Their results were published last week in Nature Communications.
“The rocks we’ve extracted are distinctly different from these types of rocks that we already know about,” said study co-author Ivan Savov, a geochemist and volcanologist at the University of Leeds. press release“In fact, they may be as different from the known basalt on the ocean floor as the Earth’s basalt is that of the Moon’s basalt.”
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Basalt is a 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, was likely formed towards the end of the fleeting beginning of the Ring of Fire. It has previously gone unnoticed due to its extremely remote (and difficult to access) location.
Although old, 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 platform capable of taking samples from six miles below the surface. (Not quite at a depth of 5 miles, the newly reported basalt didn’t even push the limits of the drill rig.) Under a microscope, a cross-section of the rock looks like a still image from a kaleidoscope, a conglomeration of slate grays and sea vegetables. It comes from the Amami Sankaku Basin, some 600 miles off the coast of Japan. Savov said knowing the conditions that formed this basalt will help earth scientists better understand the development of the larger formation from which it has been drawn.
“In an age when we rightly admire discoveries made through space exploration, our findings show that there are still many discoveries to be made on our own planet,” Savov said in the university press release.
Rocks can tell us a lot about the history of the planet. Recently, scientists examining rocks in Greenland discovered evidence of one magma ocean it existed when the earth was a baby, not long after the moon was formed.