New research indicates that the Red Sea may not be a sea at all, because it is spreading like an ocean basin and has reached its young adulthood after 13 million years.
Researchers drawing on a new approach to study the enigmatic sea, situated between Northeast Africa and the Arabian Peninsula, have concluded that it bears more similarity to other oceans than other seas. It is like any other ocean, tectonically speaking, merely younger, challenging prior notions suggesting that the Red Sea is unique among other ocean basins.
The Red Sea is smaller than Earth's major oceans and partially enclosed by land, characteristic of a typical sea. But the authors of the new study, published April 23 in Nature Communications, say the Red Sea has geological features typical of oceans, including the spreading of its seafloor and the volcanoes in its midocean ridge.
"The things that we mapped did not match the classroom books that we knew from our studies," said lead author Nico Augustin, a marine geologist at GEOMAR Helmholtz Centre for Ocean Research, in Germany. "So we basically said, 'Well, it's not fitting what I see here,' and that's when we started to look a little bit closer to the Red Sea."
The geological model of the Red Sea remains a controversial subject among scientists. Buried under a thick layer of salt and sediment, kilometers-long at some points, the Red Sea is difficult to analyze. Prior models relied on geological measurements that the salt deposits could obscure.
To circumvent this problem, Augustin and his colleagues approached the Red Sea with more direct geological measurements: They relied on earthquake data, as well as gravity gradient data and high-resolution bathymetry, a measurement of water depth that can produce maps of the seafloor.
Earthquakes can show where the seafloor may be spreading apart. In a typical ocean, the seafloor spreads out along an axis where tectonic plates are moving away from each other. Gravity data helps detect changing crust types, such as continental crust or oceanic crust, as well as their thickness, because gravitational forces shift where crust changes from oceanic to continental.
Drawing on this information, Augustin and his colleagues could tell that the Red Sea is built like a standard ocean basin, with large volcanoes in the center of its midocean ridge, which is characteristic of such features in other oceans.
"We saw that the pattern that we see in the Red Sea is the same as midocean ridges elsewhere, and that's what we used," co-author Froukje van der Zwan, an assistant professor of earth science and engineering at King Abdullah University of Science and Technology, in Saudi Arabia, told The Academic Times. "We see these gravity patterns; they are the same as other oceans, so it must be an ocean. It's as simple as that."
The findings have implications for the understanding of what ocean basins are. According to Augustin, the Red Sea had been considered a special case of ocean-basin formation due to some of its unique geologic properties, such as its salt deposits, which prevented direct comparison to other basins.
In the past, the Red Sea had usually been discussed as something between an embryonic ocean and a mature ocean, because its southern area seemed to contain a mature ocean basin, while the north appeared to reflect one in an embryonic stage. But now, Augustin and his colleagues have found that oceanic crust underlies the entire Red Sea basin, which means it is not an ocean basin in the making, but rather a full ocean basin.
"Tectonically speaking, we think the Red Sea is a normal ocean basin, and that there's only one way of ocean-basin formation, which was not the case a couple of years back," Augustin said in an interview with The Academic Times. "There was thought that there are different ways of ocean-basin formation, because there was the Red Sea, and the Red Sea was always treated special. And then we came and said, 'No, it's not special. There's lots of stuff laying on top of it, but it's a normal basin.'"
These findings have implications not only for the oil industry, as the presence of oil varies in continental crust and oceanic crust, but also for the "safety" of the Red Sea, according to Augustin. He and his colleagues found that, contrary to prior studies, the Red Sea is not covered by large, strike-slip faults that could potentially destroy cities. Instead, the high-resolution bathymetric maps showed these faults only in the northern and southern areas of the Red Sea, not covering the whole central area.
In future research, Augustin and van der Zwan want to use these methods to generate a more detailed picture of the Red Sea. Next, they'll look for hydrothermal vent fields, explosion craters and tectonic borders in the southern area of the Red Sea.
And though they are confident in their approach, Augustin and van der Zwan understand that their findings will be subject to debate in the scientific community.
"I think our model at the moment fits all the observations best," van der Zwan said. "But, of course, it's still science, and things are changing, and if someone comes up with an improved model, then we are happy to discuss it further."
The study, "13 million years of seafloor spreading throughout the Red Sea Basin," published April 23 in Nature Communications, was authored by Nico Augustin and Colin W. Devey, GEOMAR Helmholtz Centre for Ocean Research; Froukje M. van der Zwan, King Abdullah University of Science and Technology; and Bryndís Brandsdóttir, University of Iceland.