Thousands of kilometers below the surface of the Earth are two huge formations, the origin of which no one can understand. Scientists call them “bubbles” and have every reason to believe that they have a huge impact on the processes occurring inside our planet. It is, in every way, a gigantic riddle that researchers have puzzled over for more than 40 years.
“Bubbles” got their not very euphonious name due to their shape – they look like irregularly shaped drops with thick rounded outgrowths. Their scientific name is Large Low Shear Areas. Difficult, isn’t it? But it says, in particular, that waves carrying any energy slow down when passing through them.
Mysterious clumps of various rocks are depicted using earthquake waves (model from French and Romanowicz, 2015, Nature). Author: Ed Garnero, Hongyu Lai, Arizona State University
“Bubbles” are located at a depth of about 2000 kilometers under the Earth’s crust. They are so huge that if they were on the surface of the planet, the International Space Station would have to fly around them in order not to collide. The lower edge of the bubbles is located at the point of contact between the mantle and the molten outer core. To get the latest stories, install our app here.
In the 70s, scientists discovered one of them under the Pacific Ocean, and the second – under Africa and part of the Atlantic Ocean. These regions are known to differ from the surrounding mantle material, as seismic waves move through them more slowly. But many questions still remain unanswered.
No one knows where they came from, when they appeared and what role they play. Hypotheses for 40 years put forward abound. One of them describes these bubbles as ejections of hot rising rocks pouring into volcanoes on the Earth’s surface, and with them forming islands such as Hawaii and Iceland.
The second suggests that they “break” the Earth’s magnetic field. The third tie them to supervolcanoes, which caused several very catastrophic periods in the history of the Earth. As you can see, the range of estimates here is great, from complete harmlessness to the very apocalypse. To get the latest stories, install our app here.