Earth is a dynamic planet: its continental plates have been wandering since their existence, pushing each other outwards and into each other, causing mountain ranges to rise in the event of collisions and open up gaping cracks in the oceans from behind. But once upon a time, over a period of nearly a billion years, there was apparently a strange lull during the formation of the mountain formation: in the Middle Ages about 1.8 to 0.8 billion years ago the movement of tectonic plates slowed and stopped. With obvious consequences, because ultimately land masses around the world were fairly flat after wind and weather made all of the ancient mountain masses disappear through erosion. This could potentially lead to a chain reaction with consequences for life in the ocean, ushering in a stage that was notorious for evolutionary biologists and geologists, and which Chinese researchers have now managed to narrow down in the specialized journal Science.
Scientists led by Ming Tang of Peking University in China investigated geological processes in the middle layer of proterozoic by determining changes in the thickness and composition of the Earth’s crust. They have one of them for that A method recently presented in “Geology” Used to determine the isotope distribution of europium in zirconium minerals from the earth’s crust. Zircon is found all over the world in the crust, where it crystallizes at different times. The researchers were able to show that the ratio of europium allows to draw inferences about the thickness of the crust at the site at the time it crystallized – and thus they have now been able to estimate the location and time of the crust that is particularly thick or thin. It was also evident that the thick crust at the surface was raising higher mountains as compressive earth plates developed their strength here.
By analyzing europium zirconium, Tang’s team was able to establish a timescale of continental crust thickness at various points on all continents, which dates back to the early days of plate tectonics. The average thickness around the world fluctuates greatly: the strongest crust on Earth was formed in the Archaeological Age 4 to 2.5 billion years ago and in the Paleozoic Era, that is, from 540 million years ago to today. However, in the middle primary layer, continental crust was remarkably thin globally. At that time, the researchers concluded that the formation, that is, the rise of mountains, had almost stopped.
Indeed, evolutionary biologists were familiar with this era: according to evidence, the speed of development of new forms of life in the oceans has slowed dramatically. It’s easy to imagine, says Tang and Co., that this is linked to stopping the formation of mountains in the long-lived supercontinent Nona Rodinia, which formed at the time. However, dynamic processes in the lithosphere appear to have frozen. Then the mountains were gradually removed by erosion processes until the earth became substantially flat all over the world than it is today. Then erosion continued, but for a long time it no longer guaranteed the transport of essential nutrients such as phosphates from land to the oceans.
This lack of supplies could have led to a fairly steady path of evolutionary processes at sea. Eukaryotic cells with cellular nuclei and cell structures were already in existence 1.7 billion years ago, but they only produced many new variants about 0.8 billion years ago. So the evolutionary gap could have been related to the flat Earth.
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