When sea level is highest

Scientists cannot answer this question with 100 percent accuracy, but they have a few guesses. For example, a study by geologist Douwe van der Meer of Utrecht University in the Netherlands indicates that sea levels probably peaked in the last half-billion years. 117 million years agoDuring the Aptian period. During this period, which was part of the Cretaceous Period (145-66 million years ago), sea level was approximately 200 meters higherthan today. Dinosaurs still roamed the Earth at that time.

Jun Korenaga, Professor of Earth and Planetary Sciences at Yale University, has a slightly different view. His research shows that Sea levels were even higher much earlier in Earth’s historyIn total, it is approximately 4.5 billion years old. According to him, this happened when the first continents were just forming. At that time, there was almost no land on the Earth’s surface.

• In the short term, sea level depends on melting ice. For example, if Antarctica’s Thwaites Glacier, also known as the Doomsday Glacier, melted, the entire West Antarctic Ice Sheet could collapse, causing the average global sea level to rise by about 3.4 meters.
• In the long term, continental drift and seafloor stretching also come into play.

And then there are the unpredictable factors: Korenaga believes the early oceans contained more water than today. Oceans may have gradually flowed into Earth’s mantle since the planet’s birth.

The last time sea level was higher than now was about 120,000 years agoDuring the last interglacial period (130,000 to 115,000 years ago), when modern humans still shared the planet with our Neanderthal and Denisovan relatives. During this time, a warmer climate caused the Antarctic ice sheets to melt, leading to sea level rising approximately 6 meters above the current average level. The climate then warmed due to projected changes in the Earth’s orbit. Today, ice is melting due to humans burning fossil fuels, and the amount of carbon dioxide and other greenhouse gases in the atmosphere that are warming the planet is rapidly increasing.

In any case, melting ice means rising sea levels. However, during both periods, Earth experienced a long ice age during which polar ice ages existed on the planet. Between major ice ages, Earth may lose its polar ice caps. By the time the Earth is completely (or almost) free of ice, sea level could be 10 times higher than it was during the last interglacial period.

If you go back about 50 million years, there was no ice in Greenland, there was no ice in Antarctica. Sea level rose by about 70 meters
said van der Meer.

The scientist adds that although sea levels were highest when ice levels were lowest, this does not fully explain the huge oceans of the Cretaceous period, when 30% of modern landmasses were under water. Plate tectonics also played a role at that time. Specifically, van der Meer estimates that sea levels were highest during the period when South America was moving away from Africa. about 200 to 100 million years ago.

Tectonics also played a role

These continents were separated from each other by the formation of the South Atlantic Ocean between them. New oceans tend to be shallower than the oceans they replace, Van der Meer said. Above a layer of hot, semi-liquid rock called magma lies the crust, which is divided into large plates that appear to float above it. The magma that rises to the surface solidifies and forms a new crust. When this happens, it may push the edge of the old slab back to make room.

Ancient oceanic crust is dense. Van der Meer says it pushes the magma underneath with greater force, causing deep oceans to form. The new crust had less time to solidify because it now had a layer of cold water on top. Therefore it is more buoyant and new oceans are shallower. This affects sea level.

The Cretaceous period combined the absence of polar ice with shallow water, resulting in the highest sea level in half a billion years. This time period, the Phanerozoic Era (541 million years ago to the present), is the most studied period because it is the period when complex life and its fossils became common. Some of these fossils have turned into oil and gas reserves, and fossil fuel companies have long been mining past sea levels to learn where to look for them.

more water

As the movement of lithospheric plates absorbs old crust and replaces it with new, it is becoming increasingly rare for scientists and geological history to collect data. Korenaga examines the Hadean and Archaean ages, the oldest periods of Earth history.

High levels of radioactive compounds in early rocks indicate that: The first continents were hotter, weaker, and not yet strong enough to hold their shape. Before the continents solidified, volcanic islands may have been a single landmass.

Korenaga and his colleagues calculated that: The Earth’s surface originally contained twice as much water as it does today. Like oceanic plates, water can move in and out of magma beneath the Earth’s crust. Korenaga’s calculations indicate a massive loss of water from the surface oceans over billions of years.

If this is true, their golden age will likely be behind them, although the seas will continue to rise. The world’s first seas were the highest seas because there was more water.