The movement of tectonic plates has long been known to shape the rocky features of Earth’s surface. However, recent research indicates that the mantle layer underneath the plates also exerts a significant influence on the topography of Earth. This subtle influence, known as residual topography, can be seen in various locations far from tectonic plate edges.
Stephenson and colleagues have recently conducted a study, published in the Journal of Geophysical Research: Solid Earth, where they created two new databases to better understand how the mantle affects topography. These databases compile measurements of crust thickness and seismic velocity from around the globe, along with laboratory analysis of seismic velocity as a function of temperature, density, and pressure.
By analyzing these measurements, the researchers were able to disentangle crustal influences on topography from mantle influences and identify residual topography. They found that differences in the temperature and chemical structure of the mantle can cause swells and basins in the landscape, distinct from those that form at the edges of tectonic plates.
These swells and basins can rise or fall by up to 2 kilometers and stretch for hundreds to thousands of kilometers within the interior of plates. Some of the highest swells can be found in regions like the Afar-Yemen-Red Sea region, western North America, and Iceland, while the deepest basins are found near the Black, Caspian, and Aral seas, as well as in the East European Plain. This pattern of topographical features may control the locations where significant erosion and sedimentary deposition occur, impacting important geological processes.
The researchers suggest that these findings could help explain the existence of magmatism found far from plate boundaries. Additionally, understanding the effects of flow in Earth’s mantle on the surface through geologic time could provide valuable insights into the complex processes that shape our planet’s topography.
Overall, this study highlights the intricate relationship between the mantle and Earth’s topography, shedding light on the hidden forces that contribute to the formation of landscapes across the globe. By unraveling the mysteries of residual topography, scientists can deepen their understanding of the dynamic processes that have sculpted the surface of our planet over millions of years.