The cyclical strengthening and weakening of the tides over ten million years is probably linked to another, longer cycle: the formation of supercontinents of the Earth every 400 to 600 million years, according to a new study. According to the authors of the study, the new findings have an impact on the formation of our planet, its climate and the evolution of life on earth.
The new research suggests long-term changes in tidal energy that control the strength of the oceans. Waves are part of a super-tidal cycle dictated by the movement of tectonic plates.
When tectonic plates shift, sink and shift continents of the earth to form large land masses or supercontinents, ocean basins open and close. When these basins change their shape, they can hit shapes that reinforce and amplify their tides.
In the new study, tide simulations projected hundreds of millions of years into the future suggest that the Earth is currently at a tidal maximum, where strong tides persist for approximately 20 million years. The oceans will go through several tidal cycles, while the next supercontinents will form over the next 250 million years. Eventually, the tides will become much weaker, just as with the two recent supercontinents Pangea and Rodinia, according to the new study, which was published in Geophysical Research Letters a journal of the American Geophysical
Scientists knew that Tidal energy in the distant past varied, but the new study suggests that there is a tidal super-tidal cycle associated with tectonic movements.
"Our simulations indicate unusually large at the moment," said oceanographer Mattias Green of Bangor University's School of Ocean Sciences at Menai Bridge in the UK and lead author of the new study. "And that was really our motivational question: if the tides were weak until 200 million years ago and they've been increasing dramatically in the last two million years, what will happen if we pull millions of years into the desert?" Tidal power is linked to life on earth, and understanding the cyclical evolution of the ocean is, according to the authors of the study, ready to improve scientists' understanding of evolutionary history. In times of strong tidal energy, as today, strong waves stir the sea and create the nutrient mixture needed to sustain life in the ocean. As the earth's landmasses slowly move toward a supercontinent configuration, the ocean basins of the planet open up to form an uninterrupted body of water. Such a sea would have a low tidal energy. Weak waves mean that there is less nutrient mixing that could create an oxygen-hungry seabed that is largely depleted of life, similar to a pool of stagnant water, according to the new study. The movement stands for many disciplines, from evolutionary biology to the global nutrient cycle said geophysicist Dietmar Müller of the University of Sydney in Australia, who was not involved in the new study.
"It probably means nothing to people now in our lives," said Muller. "But it does improve our understanding of the interactions between plate tectonics, the Earth's climate system, its oceans, and even how the evolution of life is at least partially driven by this tidal process." [1
Changing Continents, Ocean Basins
Each of the continents of the earth rides on huge plates known as tectonic plates. These plates move for hundreds of millions of years, meeting various continental configurations.
Tectonic plates determine the shape and arrangement of continents, but also determine the shape of ocean basins. As the North American and Eurasian plates drift apart, the Atlantic Ocean expands between them and also changes its shape.
The change in the shape of the ocean basins causes a change in a property known as resonance. When a basin is resonant, the energy from the gravitational attraction of the moon coincides with the length of the ocean basin and causes an increase in the tidal energy.
Green represents the resonance of a child on a swing. A swinging child only needs a small push from an adult at the right time to keep the momentum higher and higher. "You force it with the same frequency as the natural vibration, and the same happens in the ocean."
A Tectonic Timeline
In the new study, scientists simulated the movement of the Earth's tectonic plates and changes in ocean basin resonance over millions of years.
The new research suggests that the Atlantic Ocean is currently resonant, causing the tides of the ocean to approach maximum energy levels. Over the next 50 million years, the tides in the North Atlantic and Pacific will resonate and grow stronger. During this time, Asia will divide and create a new sea basin, the study said.
In 100 million years, the Indian Ocean, the Pacific Ocean, and a newly formed Pan-Asian Ocean will see greater resonance and tidal tides. Australia will move north to join the lower half of Asia, as all continents are slowly merging into a single land mass in the northern hemisphere, the new study says.
After 150 million years, the tidal energy begins to sink like that of the earth Landmasses form the next supercontinent and the resonance decreases. In 250 million years, the new supercontinent will have formed, resulting in an age of low resonance, resulting in low tidal energy and a largely calm sea.
The new study shows that each tidal maximum lasts at most 50 million years and is not necessarily in phase with the supercontinent cycle.
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doi: 10.1029 /.