An international research team from Germany and China has revealed the nature of the phenomenon of many shallow holes covering the floor of the North Sea. Its origins have attracted the attention of scientists for many years. The article was published in the scientific journal magazine Contact Earth and Environment (CEE).
In the North Sea, the underwater soil is dotted with hundreds of thousands, or even millions, of round or oval depressions, varying in width from a few meters to 60 meters but only 11 centimeters deep in any given area. Until recently, it was assumed that these depressions were caused by methane emissions, but this theory has its weaknesses.
According to the study’s lead author, geologist Jens Schneider von Deimling of the University of Kiel, the North Sea bottom is composed of porous sand and has strong currents, which prevents methane from accumulating in bottom sediments. This was confirmed by the results of the search, in which scientists scanned thousands of kilometers using echo sounders and found no traces of gas.
A new study has shown that holes in the North Sea were likely dug by porpoises, a marine mammal similar to dolphins. Experts believe that marine mammals plow the ground in search of sand eels.
This hypothesis was confirmed by analysis of models for estimating the habitats of eels and porpoises, as well as bottom work using echolocation, which showed numerous depressions in the distribution areas of both species.
However, scientists were not able to film the dolphins during the hunt due to the turbidity of the North Sea and the shyness of these animals.
According to the researchers, their discovery carries important information because the presence of underwater methane emissions often indicates tectonic instability in the region. However, the fact that the holes were made by porpoises points to the seismic safety of the North Sea.
Previous scientists discovered Huge underwater volcanoes off the coast of Chile and Peru.