Under the mountains of the Sierra Nevada in California, the crust takes off.
This process, called lithospheric founder, has nothing to fear. In fact, it may be how continents were formed for the first time. The continental crust is higher and lasts longer than the oceanic crust because it is less dense. The foundation could be the way in which the lighter materials in the crust separate from heavier materials, creating the continents on which all terrestrial life depends.
A new study now reveals that this process is currently occurring under Sierra Nevada. In the southern section of the mountain range, the lithosphere – the upper part of the earth’s mantle and part of the crust – has already taken off and has sank into the deeper coat, according to the new research. The lithosphere under the central Sierra is currently taking off, while the process has not yet reached the north end of the mountain range.
“You might be standing in Sierras fishing, and there could be this huge layer that takes off under you and you don’t even know,” said Vera Schulte-Pelkumgeoscientist at the University of Colorado Boulder.
There is no sign on the surface that this coat occurs. But the researchers had previously noticed bizarrely deep earthquakes under the Sierras, with magnitudes of 1.9 to 3.2 occurring more than 25 miles (40 kilometers). It’s strange, Schulte-Pelkum has told Live Science, because the rocks at this depth are generally hot and under pressure, which means that they tend to deform without breaking and released seismic waves.
Schulte-Pelkum and his co-author of the University of California San Diego Sismologist Deborah Kilblooked at the recordings of earthquakes in the region from 1985 to 2023. They used the waves of these earthquakes to glean information on the deep crust and the upper coat under the mountains. They perfected a measure called anisotropy, which reveals a difference in the way the waves move according to the direction they come. This can reveal information on the orientation of rock.
The results revealed a layer between 25 and 43 miles (40 to 70 km) where the rocks were crushed over. In the south of Sierra, near Sequoia National Park, this layer had disappeared, and in the north of the Sierra, around Lake Tahoe, it was not shealed. But in the center of Sierra, in Yosemite National Park, the layer actively falls into the coat.
Apprevious research had suggested that this coat could have occurred under the south of southern Sierra 3 million or 4 million years ago, said Schulte-Pelkum. “Now we say:” I think it continues “, she said,” so we are somehow attracting the act. “
The researchers reported their results in December in the journal Geophysical research letters. The same process of building the continental crust could occur elsewhere in the world, said Schulte-Pelkum, including in New Zealand, on the Anatolian plateau in Turkey and in the Mountains of Carpathians in Eastern Europe.
“We could go and get this in a number of other places where people have proposed that the lithosphere was perhaps thicker and took off now,” she said.