Exeter College Fellow co-authors new study on Earth’s deep mantle
Exeter College Tutorial Fellow in Earth Sciences, Dr Paula Koelemeijer, has recently co-authored a new study along with colleagues from Cardiff University, the University of Bristol, and the University of Michigan. It has revealed that two continent-size regions in Earth’s deep mantle have distinctive histories and resulting chemical composition, in contrast to the common assumption they are the same. The findings are available to read in the journal Nature Scientific Reports.
Seismologists have long known that seismic waves – generated by earthquakes – do not travel through all parts of Earth’s interior at the same speed and deep inside the mantle (the layer between Earth’s iron core and its silica-dominated crust), there are vast areas beneath the Pacific Ocean and the African continent where seismic waves travel much slower than average. These “Large-Low-Velocity-Provinces” (LLVPs) are bigger than continents, up to 900 kilometres in height and thousands of kilometres wide.
One common hypothesis is that the LLVPs are made up of oceanic crust that was pushed into the mantle at subduction zones. This crustal material was then stirred through the mantle over millions of years and accumulated to form the LLVPs.
Researchers have typically assumed that both LLVPs are similar to each other in nature, but this new work has challenged this view by modelling the formation of the LLVPs through time.
“The fact that these two LLVPs differ in composition, but not in temperature is key to the story and explains why they appear to be the same seismically. It is also fascinating to see the links between the movements of plates on the Earth’s surface and structures 3000 km deep in our planet.”
– Dr Paula Koelemeijer
