Studies have shown that a large amount of minerals and water is stored in the mantle.
Introduction: Research suggests that the Earth's surface may have been completely submerged by water, and scientists believe that the entire mantle of the Earth can hold 2.3 times the amount of water contained in the oceans on the Earth's surface.
An ingenious new study combining physical models and experiments, with growing evidence suggests that the Earth was a world of water billions of years ago, when the Earth was covered in vast amounts of water that were twice as much as the current surface water, even submerged over its highest peaks.
It's not evidence, but things really start to prove that that's what it is.
The mystery is on the mantle. The mantle is an extremely hot, non-melting layer of rock that extends down nearly 3,000 kilometers beneath the relatively thin crust, accounting for two-thirds of the Earth's mass. Extremely high pressures and temperatures on the mantle create minerals that are not found on the surface, such as wadsleyite, ringwoodite, and bridgmanite olivine.
Image source: T. Kawazoe
These minerals have a water storage structure that can store up to three percent of their own weight of water. That doesn't sound like a lot either, but don't forget, the mantle makes up most of the Earth's mass. There are a lot of these minerals there, and they store a lot of water.
The earth's main layer consists of a thin rock crust (8-40 km), a mantle with extremely high temperatures but solid rock (2900 km), an outer core of liquid metal (2250 km), and a core of solid metal (1300 km). Source: Getty Images / anuwat meereewee.
The key question is, how much water do they store now and how much could they store in the past? Experiments have simulated the mantle, where scientists crush minerals with diamond anvils, then heat them to high temperatures and measure how much water they have to store water.
How diamond anvil works, Source: Teach The Earth
The new study mainly looks at the water storage capacity of those minerals at different pressures and temperatures, and uses the behavior patterns of minerals to fit the data. Their findings are considerable: the Earth's overall mantle holds 2.3 times the mass of today's surface oceans, more accurately between 1.9 and 4.4 times, and the average is 2.3 times. In other words, if you want to take all the water out of the balloon — about 1.4x10^18 tons, plus 17 zeros tonnage after 14 — the minerals in the mantle can store more than twice as much water.
It can and stores so much water now. In the past, the mantle was warmer than it is now, which is what makes the new study interesting. The temperature of the mantle was about 300 degrees Celsius higher than it is today 300-4 billion years ago (today's temperature is about 1300 degrees Celsius). Going back to experiments and through their models, the scientists found that if the minerals were warmer, they stored less water. The storage capacity of hotter minerals is only between 0.52-1.69 times the mass of the current surface oceans, with an average of 0.8 times.
That's noticeably less. If the maximum amount of water in the mantle is correct today, it means that in the past the mantle contained less water than it does now. That is to say, so much water in the mantle now must have come from somewhere.
The Rift Valley (right) is where the tectonic plates split. The subduction zone (left) is the area where one plate dives into the mantle below another. Getty Images / Christoph Burgstedt / Science Photo Library.
Scientists hypothesize that in ancient times, there was more water on the surface, possibly twice as much as there is now. This water seeps into cracks in the earth's crust, which may weaken the earth's crust, and plate tectonics begin for the first time. When one plate slides with surface water underneath another, the water is stored in the mantle. As time passed, the mantle cooled, and it could hold more and more water, because as the mantle cooled down, the Watts and Lynnwood stones were also easier to form, so they helped the mantle hold more water. Over time, the mantle absorbed about half of the water on the surface to have the world we see today.
It wasn't until I read this paper that I learned that surface water penetrates deep into the mantle through invisibility, and then the volcano releases the water in the mantle. The net effect of this cyclical exchange process is that the surface water is lost into the mantle, which is estimated to be as much as one billion tons per year! It really shocked me.
This is equivalent to a cubic kilometer per year. It may look like a lot, but it's just a drizzle for the vast ocean. However, after a billion years that has also accumulated a lot. The net amount of exchange changes over time, which is indisputable, but over the lifetime of the Earth, these losses have halved the surface oceans*.
There is other evidence that there was more water on the surface of ancient times. These include variations in isotopic ratios and other mineralogical studies (if this sounds familiar, mars may have happened billions of years ago).
When the Earth was very young, it could have been covered in water, as shown in the image: Getty Images/Marc Ward/Stocktrek Images
"Water Earth" has been an interesting concept in recent years, and there are also movies that use this as a background. It's not just a caprice, it can also change our perception of the origin of life. One theory about the origin of life is that organic molecules and other matter are concentrated in tidal pools on land, where they mix together and become more complex, and eventually even biological states emerge. None of this would have happened without land. On the other hand, this could reinforce the theory that life is formed by hot vents deep within the ocean floor, where chemicals and heat erupt from deep in the earth's crust can do just that.
Undersea hot springs, source: Wikipedia
Is our existence due to a slightly warmer mantle and strange minerals like Wattsli, Lynnwood, and Bridgeman's, which have only recently been discovered?
It's hard to imagine that Earth can reach such a delicate state of equilibrium, but we're here aren't we? Our biosphere is fragile, subject to countless forces that can make a huge difference. I think that's a very important point that we need to keep in mind.
*Asterisk Supplement: It used to be like this. As a result of global warming, the ice sheets of the Arctic, Antarctica, and Greenland have melted, causing surface water to increase at an average of 150 billion tonnes per year, far exceeding the amount lost to the mantle.
BY: Phil Plait
FY: Green mountains and green water
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