Rocks from the Rio Grande continental rift have revealed new evidence for how continents remain stable over billions of years. A Continental rift is the belt or zone of the continental lithosphere where the extensional deformation (rifting) is occurring. These zones have important consequences and geological features, and can lead to the formation of new ocean basins.
In this case the researchers can see what is happening in the deep crust nearly 19 miles below the surface of the Earth. They have linked this evidence with tectonic processes happening today which could represent an important step in the development of stable continents.
The team led by Penn State scientists, found evidence that heat from the mantle is melting the lower crust at the rift, where tectonic forces are pulling apart and thinning the lithosphere, or crust and upper mantle.
Their research suggests that the thinning lithosphere may be more important than previously recognized for stabilizing continents and preventing them from sinking back into the mantle.
Earth’s continents have a unique silicon-rich, buoyant crust that allows land to rise above sea level. The crust also contains heat producing elements like uranium.
Heating the crust creates molten rock that carries those elements toward the surface, resulting in a cooler and stronger lower crust that can protect continents from being absorbed into the mantle.
“We are suggesting that thinning of the lithosphere is really the removal of a barrier that keeps heat away from the crust,” said Andrew Smye, one of the researchers.
https://phys.org/news/2020-10-glimpse-deep-earth-crust-source.html