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How the Ocean Inside the Mantle Affects the Habitability of the Earth

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Hidden inside the Earth—within the first several hundred kilometers below the crust—there is another ocean. It is, most likely, the largest ocean in the world. This water is not sloshing around in a big pool. No fish plumb its depths. In fact, this ocean is only water in the loosest sense: broken into its composite hydrogen and oxygen atoms and chemically bound to the surrounding rock, this ocean is in storage. Or, most of it is.

Denis Andrault and Nathalie Bolfan-Casanova, geoscientists at the University of Clermont Auvergne in France, have developed a new model that shows more of this water is in transit than previously thought. When the solid rock in the mantle—the layer of the planet between the crust and the core—becomes saturated with chemically dissociated water, it can transform into a water-rich molten slurry. When it does, it seeps back up toward the crust. The researchers call this mantle rain.

Much as the cycling of water between the atmosphere, glaciers, lakes, rivers, aquifers, and the ocean affects the level of the sea, the abundance of rain, and the frequency of drought, the exchange of water between the mantle and the surface also dictates the habitability of the Earth. Scientists already know that water can be dragged down to the mantle by subducting tectonic plates and brought back to the surface by things like volcanic eruptions, hydrothermal vents, and the creation of new crust at oceanic spreading centers. If this deep water cycle between the mantle and the surface is in balance, Earth’s sea level remains stable. If not, our planet could exist as anything from a singular global ocean to a desiccated world.

Earth’s habitability has benefited greatly from the fact that Earth’s sea levels have remained relatively stable over billions of years. According to previous studies of the mantle, however, it could have been very different. Estimates based on previously understood mechanics of the deep water cycle suggest that nearly twice as much water is carried into the mantle as is released back to the surface.

“There is a layer about 410 kilometers below the surface that can hold a lot of water,” says Andrault. The prevailing understanding says that water should stay there forever, he says. If that were the case, the Earth’s surface water would have slowly decreased, locked away in the mantle.

But that’s where mantle rain comes in.

In their study, Andrault and Bolfan-Casanova show that mantle rain could be enough to keep the deep water cycle in balance.

To discover mantle rain, the researchers looked at what happens when a subducting slab of rock and rock-bound water sinks deeper into the mantle. They found that as it descends, increasing temperatures and pressures cause the rocks to melt, releasing the water.

“The melt is like a slurry,” says Andrault. “Imagine a mushy mix of sand grains glued to each other with mud in between—the mud is the mantle rain.”

As more rocks melt, and as more water is liberated from the rock, this melt eventually becomes light enough that it begins to rise. As it does, the water bonds to minerals in the upper mantle and lowers their melting points, causing more melting that releases more water—and the cycle continues.

Andrault and Bolfan-Casanova’s model of mantle rain, says Yoshinori Miyazaki, an earth and planetary scientist at the California Institute of Technology who was not involved in the study, “shows there could be another way to transport water towards the surface in addition to the global-scale convection of the mantle itself.”

“Water generally doesn’t like to be in the rock phase,” Miyazaki says. “It will happily escape to the melt phase and percolate upwards.” Andrault says more work is needed to understand the extent to which water is escaping in this way.

The mantle rain model also suggests that there is currently one ocean mass in the upper mantle. “Together with the ocean on the surface,” says Andrault, “this ensures that there will always be water on Earth’s surface.”

“We still have a lot to learn about the deep water cycle,” says Miyazaki. “But one certain fact is that it has worked in an amazing way to keep Earth’s average sea level relatively constant over the past 500 million years, and probably longer, to sustain a habitable environment for life to continue.”

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The body of a Ugandan Olympic athlete who was set on fire by her partner is received by family

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NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.

Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.

She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.

Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.

“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.

It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.

Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.

Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.

Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.

“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.

He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.

Kenya’s high rates of violence against women have prompted marches by ordinary citizens in towns and cities this year.

Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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B.C. sets up a panel on bear deaths, will review conservation officer training

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VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.

Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”

Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.

“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.

B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.

Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.

Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.

Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.

“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”

Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”

“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.

Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.

“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.

This report by The Canadian Press was first published Sept. 9, 2024.

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