New basalt just fell. An international team of scientists drilled nearly a mile into the Pacific seafloor and extracted a variety of chemically and mineralogically different volcanic rock from any previously known type.
The team examined a 49-million-year-old stone outcrop that formed just a couple of million years after the Ring of Fire, that famous crescent of volcanic activity that borders the Pacific Rim. For the first millions of years after ignition, the ring bubbled with a superheated intensity that, according to the team, formed a unique type of stone.
They collected this evidence of Earth’s history from almost 5 miles below the surface of the ocean. Their analysis suggests that the fires that forged the rock were hotter and more expansive than previously thought. His results were published last week in Nature Communications.
“The rocks that we recover are clearly different from the rocks of this type that we already know,” said co-author Ivan Savov, a geochemist and volcanologist at the University of Leeds, at a university. Press release. “In fact, they can be as different from known ocean floor basalts on Earth as basalts on Earth are from basalts on the Moon.”
Basalt is a very common type of igneous rock that emerges from cooled lava flows, even 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 volatile beginnings of the Ring of Fire. It had previously gone undetected due to its extremely remote (and difficult to access) location.
Although ancient, the Ring of Fire is young in terms of Earth’s tectonic history. Some volcanic rocks date back billions of years, much older than the new rock’s 49 million years of existence.
The team drilled the sample with the JOIDES resolution, a drilling rig capable of extracting samples from 6 miles below the surface. (Not at a depth of 5 miles, the newly reported basalt wasn’t even exceeding the shelf limits.) Under a microscope, a cross section of the stone looks like a frozen frame of a kaleidoscope, a conglomeration of slate gray and sea vegetables. It comes from the Amami Sankaku basin, about 600 miles 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 mined.
“In an era in which 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 statement.
Rocks can tell us a lot about the history of the planet. Recently, scientists examining rocks in Greenland discovered evidence of a magma ocean that existed when the Earth was just a baby, not long after the formation of the Moon.