Scientists are trying to understand how climate change is related to rising sea levels. There have been periods in the history of the Earth when a colossal amount of water that penetrated the Earth's mantle played a large role in the formation of the ocean level, and this was due to the destruction of the Pangea supercontinent. What processes are taking place today and how will they affect the climate?
The ocean is a large bathtub containing 1.3 billion cubic meters of water (326 million cubic miles), and it looks like someone opened the drain. Every day, hundreds of millions of liters (gallons) of water rush from the ocean floor towards the Earth's mantle, thus forming part of a very humid regeneration process that scientists call the deep-sea cycle. Here's how it works: First, water penetrates the solid surface layer at the bottom of the ocean and into minerals, which then together are sent into the Earth where tectonic plates collide. A certain part of this water remains somewhere (in some studies it is suggested that such an amount of water seeps down to the level of the Earth's mantle, which can be contained in two oceans)however, a significant amount of water returns to the surface through submarine volcanoes and hydrothermal vents.
Such a system cannot be called perfect, and scientists believe that at present much more water reaches the Earth's mantle than is thrown out to the surface - but there are no problems here. In general, this cycle represents only one element of the system that determines the rise or fall of the ocean level.
In a study published May 17 this year in the journal Geochemistry, Geophysics and Geosystems, the authors report that this element may be more important than previously thought. By modeling the currents in deep-sea cycles over the past 230 million years, the authors of this study discovered that there have been periods in the history of the Earth when colossal amounts of water seeping into the Earth's mantle played a very large role in the formation of sea level; during such periods, deep-sea cycles alone could cause a 130-meter (430 ft) drop in sea level, and this was due to a very significant factor - the destruction of the supercontinent called Pangea (Pangea).
“The Pangea split has been associated with periods of rapid tectonic shear,” said Krister Karlsen of the University's Center for Earth Evolution and Dynamics in an interview with Live Science. the city of Oslo and the head of the group of authors of the study. "This led to periods of large amounts of water leaving the Earth's mantle, which caused the associated lowering of the sea level."
The death of the supercontinent
About 200 million years ago, the supercontinent Pangea (it consisted of the seven continents we know today) began to split, and huge parts of the land began to spread in different directions. When these continental plates parted, new oceans were formed (it all started with the Atlantic Ocean, about 175 million years ago), huge cracks began to form on the seabed, and parts of the ancient underwater crust rushed into the voids formed. A colossal amount of water was trapped between pieces of the earth's crust, which moved from the surface of our planet to its depths.
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Based on previous research on Earth's tectonic strata over the past 230 million years, the researchers modeled the approximate amount of water that would go into the Earth's mantle and then leave it. The faster the water-saturated platform plunged into the depths of the Earth, the further it plunged until the water contained in it evaporated due to the high temperature of the Earth's mantle. According to the calculations of this group of researchers, such a situation sufficiently contributed to the creation of an imbalance, which led to the loss of colossal amounts of water over millions of years.
Of course, deep currents are not the only influences on sea level, says Carlsen, and this study does not take into account processes that can determine sea level, such as climate change or the size of the ice cover. Even when a huge amount of water plunges into the Earth's mantle, the real sea level can rise sharply and also drop sharply (up to tens of meters), and these periods can be much shorter.
The ocean is currently within a different period of sea level rise, and this is mainly due to anthropogenic climate change (there are different estimates, however sea level is likely to rise by 2-5 centimeters (6-16 feet) over the next century). Unfortunately, all of these millions of gallons of seawater currently rushing towards the Earth's mantle cannot protect us from this dangerous trend.
“While deep water cycles can indeed change sea level over hundreds of millions or even billions of years, climate change can affect sea level between zero and 100 years,” Carlsen said. - For comparison, the current sea level rise associated with climate change is approximately 3.2 millimeters (0.1 inches) per year. Whereas the decrease in sea level associated with deep-sea cycles is about 1/10000 of this value."
Brandon Specktor
