Measure the internal temperature of the Earth with underwater volcanic rock


Tracing the chemical history of thousands of samples of erupted material along ocean ridges has been used by MIT geologists to estimate the Earth’s interior temperature.

Their analysis shows that the temperature of the Earth’s underlying ocean ridges is relatively constant, around 1,350 degrees Celsius, almost as hot as the blue flame of a gas stove. However, there are “hot spots” along the ridge that can reach 1,600 degrees Celsius, comparable to the hottest lava.

The team’s results, which appear in the Geophysical Research Journal: Solid Earth, they provide a temperature map of the Earth’s interior around the mid-ocean ridges. With this map, scientists can better understand the fusion processes that give rise to underwater volcanoes and how these processes can drive the rate of plate tectonics over time.

“Plate convection and tectonics have been important processes in shaping Earth’s history,” he says. it’s a statement lead author Stephanie Brown Kerin, postdoctoral fellow in the Department of Earth, Atmospheric and Planetary Sciences (EAPS) at MIT. “Knowing the temperature along this entire chain is essential to understand the planet as a heat engine and how the Earth could be different from other planets and capable of supporting life.”


The interior temperature of the Earth has played a fundamental role in shaping the planet’s surface for hundreds of millions of years. But there has been no way to directly read this temperature tens to hundreds of kilometers below the surface. Scientists have applied indirect means to infer the temperature of the upper mantle, the layer of the Earth just below the crust. But estimates so far are inconclusive, and scientists disagree on how temperatures below the surface vary..

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For their new study, Kerin and his colleagues developed a new algorithm, called ReversePetrogen, which is designed to trace a rock’s chemical history over time, to identify its original composition of elements, and to determine the temperature at which the rock melted. initially below the surface. .

The algorithm is based on years of experiments carried out in Grove’s laboratory to reproduce and characterize the fusion processes inside the Earth. Laboratory researchers have heated rocks of various compositions, reaching various temperatures and pressures, to observe their chemical evolution. From these experiments, the team has been able to derive equations and ultimately the new algorithm, to predict relationships between temperature, pressure, and the chemical composition of a rock.

Kerin and his colleagues applied their new algorithm to rocks collected along Earth’s ocean ridges, a system of undersea volcanoes that spans more than 70,000 kilometers in length. Mid-ocean ridges are regions where tectonic plates are separated by the eruption of material from the Earth’s mantle, a process driven by underlying temperatures.

“You could effectively model the temperature of the entire interior of the Earth, based in part on the temperature at these ridges,” says Kerin. “The question is, what does the data really tell us about the temperature variation in the mantle along the entire chain?”

The data the team analyzed includes more than 13,500 samples collected along the ocean ridge system over several decades, through multiple research cruises. Each sample in the dataset is from an erupting sea glass – lava that erupted into the ocean and was instantly cooled by the surrounding water in a pristine, preserved form.

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Scientists previously identified the chemical compositions of each beaker in the data set. Kerin and his colleagues analyzed the chemical compositions of each sample through their algorithm to determine the temperature at which each glass originally melted in the mantle.

In this way, the team was able to generate a map of mantle temperatures throughout the entire ocean ridge system. From this map, they observed that much of the mantle is relatively homogeneous, with an average temperature of around 1,350 degrees Celsius. However, there are “hot spots” or regions along the ridge, where temperatures in the mantle appear significantly higher, around 1,600 degrees Celsius.

“People think of hot spots as regions of the mantle where it is hotter and where material can melt more and potentially rise faster, and we don’t know exactly why, or how much hotter they are, or what the role of the heat is. composition. in the hotspots, “says Kerin. “Some of these hot spots are on the ridge, and now we can get an idea of ​​what the hotspot variation is globally using this new technique. That tells us something fundamental about the Earth’s temperature now, and now we can think about how it has changed over time. “

Myrtle Frost

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