The discovery of rock that was once at komatiite-like temperatures suggests the remaining hot spots still may be capable of producing a surge of magma that can reshape our planet’s surface and inflict “really serious environmental effects,” Gazel said.
How serious? The magma plume that left behind the Costa Rica rock he studied was responsible for forming much of today’s Central America and the Caribbean region — and in the process, fueled a collapse of oceanic oxygen levels that wiped out much of the marine life that predated the dinosaurs, he said.
“It didn’t trigger a mass extinction on the surface of the planet, but it triggered a mass extinction under water,” Gazel said.
Don’t panic: There’s no sign that any new plume is in the works. But some of today’s volcanic hot spots, such the Hawaiian or Galapagos islands, may give scientists future clues that can open that window a bit wider, he said.
“The more we understand the past, the better we’re going to know about the present and the future of the planet,” Gazel said.
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Gazel and his colleagues, who included researchers from the United States, France, and Russia, also looked for signs of a mineral known as olivine to help them gauge the temperatures that produced the rock. Olivine contains microscopic beads of once-molten glass that’s trapped when the mineral cools; the low amount of volatile compounds remaining in that glass is an indication of how hot the material once was.
Analyzing that material pointed toward a temperature of nearly 1,600 degrees Celsius (2,900 Fahrenheit) — “something never found before,” he said. That’s about 400°C hotter than today’s mantle.
Geologists identified the Costa Rica site as an area of interest about 20 years ago. But at the time, scientists didn’t have the tools they needed to analyze the material as extensively as they do today. Improved materials, more sensitive instruments and increased access to tools like mass spectrometers have allowed scientists to peer more deeply into the rock than before, Ganzel said.
“I think our study provide irrefutable evidence that mantle plumes exist and they bring material from the deep Earth,” he said. In addition, “It’s telling us that we need to reconsider and understand better the way we think our planet and planets similar to Earth cool and evolve.”
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