There is a lot that scientists dont know about the mantle, the partly molten, partly solid layer of Earth that attains up 84 percent of countries around the world volume. We know that it’s composed of vast cycling mass of material moving around in gigantic loops called convection currents, and in-between these loops-the-loops, superheated plumes rise up through to the surface of Earth, creating near-perpetual sources of volcanism.
Without these currents, plate tectonics wouldnt have happened. There would be no crust , no continents , no volcanoes , no earthquakes, almost no atmosphere, and almost certainly no life so, understanding them is of the utmost importance. A new analyse, published in the journal Nature Geoscience, peels back another layer of this mysterious section of the planet, disclosing that these convection currents are moving 10 hours faster than most estimates.
Although we’re talking about timescales that seem unbelievably long to you or me, in geological words, the Earth’s surface bobs up and down like a yo-yo, Dr. Mark Hoggard, a postdoctoral research fellow at Cambridge’s Department of Earth Science, and the paper’s leading writer, said in a statement. Over a period of a million years, which is our standard unit of measurement, the movement of the mantle can cause the surface to move up and down by hundreds of meters.
One of the common models of mantle convection. Surachit/ Wikimedia Commons; CC BY-SA 3.0
The team of researchers from the University of Cambridge used 2,120 seismic surveys to build up a detailed picture of the mantle. Just like ice sitting atop interred bedrock, the topography of the crust can reveal what is happening beneath it.These mantle convection currents are incredibly powerful, and their upwelling can cause the Earths crust to move further skywards, just as their downwelling can cause it to sink.
By ascertaining global changes in oceanic crustal thickness, the team wasable to gain an understanding of the types of mantle currents active below it all. Geophysicists already have a somewhat in-depth picture of what the mantle is doing beneath the crust, but this study builds on this knowledge by providing more precise measurements of the velocity and size of the convective cycles.
This new global map of the mantle, the first of its kind, revealed that these supposedly gargantuan cycles are actually fairly small.Instead of being 10,000 kilometers( 6,200 miles) in duration, as many predicted, they are more often on the order of 1,000 kilometers( 621 miles ). If this is true, then it seems unusual that, at these scales, such convective cycles could cause such major changes in ocean crust height.
The dynamic topography of the world. Red indicates rises caused by upwelling mantle currents; blue indicates the opposite. The initial model is depicted in( a ), where it is overlaid atop additional geophysical observations in( b ). Hoggard et al ./ Nature Geoscience
However, the researchers realized that this discrepancy could be resolved if old ideas about the speed of mantle convection were hurled out the window. Ultimately, they reasoned that the global difference in oceanic crust height can be explained if these shorter convective cycles are actually moving around 10 hours faster than previously thought.
These results will have wider reaching implications, such as how we map the circulation of the world’s oceans in the past, which are affected by how quickly the sea floor is moving up and down and blocking the road of water currents, added Hoggard. Considering that the surface is moving much faster than we had previously thought, it could also affect things like the stability of the ice caps and help us to understand pastclimate change.