The hottest place on Earth revealed: Researchers find lava deep in the planet's mantle nears 1,600 degrees Celsius

  • Deep areas in Earth's mantle might be as hot as they were 2.5 billion years ago
  • 2.5 - 4 billion years ago, the temperature of Earth's mantle was hotter than today
  • Because Earth was hotter during this period, it's marked by the occurrence of a rock known as komatiite - superhot versions of Hawaiian-style lava flows
  • But rocks from ancient Galapagos lava shows conditions similar to komatiites
  • These rocks crystallized at a temperature nearing 2,900 degrees Fahrenheit (1,600 degrees Celsius) - as high as temperatures recorded from komatiites
  • It's a record on lava temperatures in the past 2.5 billion years, suggesting that they originated from a plume more than 90 million years ago that is still active

Researchers have discovered that deep portions of Earth's mantle might be as hot as they were more than 2.5 billion years ago. 

The study presents new, unprecedented evidence about the thermal evolution of the deep Earth, for example, during the Archean Eon - covering from 2.5 to 4 billion years ago - the temperature of Earth’s mantle - the silicate region between the crust and the outer core - was hotter than it is today. 

Because Earth was hotter during this period, this interval of geologic time is marked by the widespread of occurrence of a unique rock known as komatiite - superhot versions of Hawaiian-style lava flows. 

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An artistic interpretation of an Archean komatiite lava flow. Komatiites are a unique rock formed from superhot versions of Hawaiian-style lava flows. They were so hot that they glowed white instead of red, and they flowed on a planetary surface with very different atmospheric conditions, more similar to Venus than the planet we live on today

An artistic interpretation of an Archean komatiite lava flow. Komatiites are a unique rock formed from superhot versions of Hawaiian-style lava flows. They were so hot that they glowed white instead of red, and they flowed on a planetary surface with very different atmospheric conditions, more similar to Venus than the planet we live on today

During the Archean Eon, the Earth was hotter than it is today due to a higher amount of radioactive heat produced from the decay of elements, such as potassium, thorium, and uranium.

This led to the widespread occurrence of komatiites. 

'You can imagine a Hawaiian lava flow, only komatiites were so hot that they glowed white instead of red, and they flowed on a planetary surface with very different atmospheric conditions, more similar to Venus than the planet we live on today,' said Dr Esteban Gazel, an assistant professor with Virginia Tech's Department of Geosciences and the lead author of the study

WHAT THEY FOUND  

The study presents new, unprecedented evidence about the thermal evolution of the deep Earth. For example, during the Archean Eon - covering from 2.5 to 4 - the temperature of Earth’s mantle — the silicate region between the crust and the outer core — was hotter than it is today.

Because Earth was hotter during this period, this interval of geologic time is marked by the widespread of occurrence of a unique rock known as komatiite - superhot versions of Hawaiian-style lava flows.

Dr Gazel and his team made a discovery while studying the chemistry of ancient Galapagos-related lava flows - preserved today in Central America: Lavas that show conditions of melting and crystallization similar to the komatiites. 

They found that these olivines - the first mineral that crystallized from these lavas - crystallized at a temperature nearing 2,900 degrees Fahrenheit (1,600 degrees Celsius) - as high as temperatures recorded by olivines from komatiites - making this a record on lava temperatures in the past 2.5 billion years.

Their findings suggest that Tortugal lavas most likely originated from the hot core of the Galapagos mantle plume that started producing melts more than 90 million years ago and has remained active since then. 

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However, Earth stopped producing abundant hot komatiites after the Archean era because the mantle cooled during the past 4.5 billion years due to convective cooling and a decrease in radioactive heat production. 

But Dr Gazel and his team made a discovery while studying the chemistry of ancient Galapagos-related lava flows preserved today in Central America: Lavas that show conditions of melting and crystallization similar to the komatiites. 

Dr Gazel and his team studied a set of rocks from the 90 million-year-old 'Tortugal Suite' in Costa Rica, finding that they had magnesium concentrations as high as Archean komatiites, as well as textural evidence for extremely hot lava flow temperatures.

'Experimental studies tell us that that the magnesium concentration of basalts and komatiites is related to the initial temperature of the melt,' Dr Gazel said.

'The higher the temperature, the higher the magnesium content of a basalt.'

The researchers also studied the composition of olivine - the first mineral that crystallized from these lavas. 

Olivine - a light green mineral that Dr Gazel has explored many volcanoes in search for - is a useful tool for studying conditions related to the origin of lava flow because it's the first mineral phase that crystallizes when a mantle melt cools. 

They also carry glass that was once melt, and other smaller minerals that are helpful for answering questions about the deep Earth. 

'We used the composition of olivine as another thermometer to corroborate how hot these lavas were when they began to cool,' Dr Gazel said.

Dr Gazel and his team studied a set of rocks from the 90 million-year-old Tortugal Suite in Costa Rica, finding that they had magnesium concentrations as high as Archean komatiites, as well as textural evidence for extremely hot lava flow temperatures. Pictured are X-Ray chemical maps of olivines (rocks) at the site. They found that these olivines crystallized at a temperature nearing 2,900 degrees Fahrenheit (1,600 degrees Celsius) - as high as temperatures recorded by olivines from komatiites - making this a record on lava temperatures in the past 2.5 billion years

Dr Gazel and his team studied a set of rocks from the 90 million-year-old Tortugal Suite in Costa Rica, finding that they had magnesium concentrations as high as Archean komatiites, as well as textural evidence for extremely hot lava flow temperatures. Pictured are X-Ray chemical maps of olivines (rocks) at the site. They found that these olivines crystallized at a temperature nearing 2,900 degrees Fahrenheit (1,600 degrees Celsius) - as high as temperatures recorded by olivines from komatiites - making this a record on lava temperatures in the past 2.5 billion years

'You can determine the temperature that basaltic lava began crystallizing by analyzing the composition of olivine and inclusions of another mineral called spinel. 

'At higher temperatures, olivine will incorporate more aluminum into its structure, and spinel will incorporate more chromium. 

'If you know how much of these elements are present in each mineral, then you know the temperature at which they crystallized.'

Komatiite lava from Komati Valley, South Africa, showing the distinctive 'spinifex texture' formed by plates of olivine - a light green mineral that is the first mineral phases that crystallizes when a mantle cools. In their study, the rersearchers suggest that Earth may still be capable of producing komatiite

Komatiite lava from Komati Valley, South Africa, showing the distinctive 'spinifex texture' formed by plates of olivine - a light green mineral that is the first mineral phases that crystallizes when a mantle cools. In their study, the rersearchers suggest that Earth may still be capable of producing komatiite

The researchers found that Tortugal olivines crystallized at a temperature nearing 2,900 degrees Fahrenheit (1,600 degrees Celsius) - as high as temperatures recorded by olivines from komatiites - making this a record on lava temperatures in the past 2.5 billion years.

In their study, the researchers suggest that Earth may still be capable of producing komatiite-like melts. 

Their findings suggest that Tortugal lavas most likely originated from the hot core of the Galapagos mantle plume that started producing melts more than 90 million years ago and has remained active since then.

A mantle plume is a deep-Earth structure that likely originates at the core-mantle boundary of the planet. 

When it nears the surface of the planet, it begins to melt, forming features known as hotspots, such as those found in Hawaii or the Galapagos.

Geologists can then study these hotspot lava flows and use their geochemical information as a window into the deep Earth.

'What is really fascinating about this study is that we show that the planet is still capable of producing lavas as hot as during the Archean time period,' Dr Gazel said.

'Based on our results from Tortugal lavas, we think that mantle plumes are "tapping" a deep, hot region of the mantle that hasn’t cooled very much since the Archean.

The study presents new, unprecedented evidence about the thermal evolution of the deep Earth, for example, during the Archean Eon — covering from 2.5 to 4 - the temperature of Earth’s mantle — the silicate region between the crust and the outer core — was hotter than it is today

The study presents new, unprecedented evidence about the thermal evolution of the deep Earth, for example, during the Archean Eon — covering from 2.5 to 4 - the temperature of Earth’s mantle — the silicate region between the crust and the outer core — was hotter than it is today

'We think that this region is probably being sustained by heat from the crystallizing core of the planet.'

'This is a really interesting discovery, and we are going to keep investigating Tortugal,' said Jarek Trela,Dr Gazel's doctoral student and the first author of the study.

'Although the Tortugal Suite was first discovered and documented more than 20 years ago, it wasn’t until now that we have the technology and experimental support to better understand the global implications of this location.'

Trela added, 'Our new data suggest that this suite of rocks offers tremendous opportunity to answer key questions regarding the accretion of the Earth, its thermal evolution, and the geochemical messages that mantle plumes bring to the surface of the planet.'

 

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