New research suggests that two colossal, continent-sized structures deep within Earth's lower mantle, dubbed "BLOBS" (big lower-mantle basal structures), are directly linked to Earth-shattering volcanic eruptions. These findings shed light on the mechanisms behind some of history's most destructive volcanic events.
Traditionally, the Earth's lower mantle, a solid layer of hot rock located thousands of kilometers beneath the surface, has been depicted as a smooth layer. However, recent studies reveal a mountainous topography, with the two BLOBS potentially composed of materials distinct from their surroundings. These hidden structures feature craggy ranges that shift and buckle, much like the tectonic plates far above them.
Volcanologist Annalise Cucchiaro from the University of Wollongong in Australia and her team have established a direct influence of these BLOBS on surface volcanic activity. When scorching columns of rock, known as deep mantle plumes, rise from depths of nearly 3,000 kilometers (almost 2,000 miles), they can trigger the kinds of catastrophic volcanic events responsible for mass extinctions, including that of the dinosaurs.
The research team confirmed the connection between BLOBS and these subterranean plumes using three different datasets detailing large volcanic eruptions that occurred approximately 300 million years ago. "This work highlights the importance of mantle plumes in acting as 'magma highways' to the surface, creating these giant eruptions," Cucchiaro stated, adding that "it also shows that these plumes move along with their source, the BLOBS."
There are two primary BLOBS within the lower mantle: one situated beneath the African hemisphere and the other under the Pacific. While it remains unclear if these BLOBS are stationary or constantly moving due to convection, the new research indicates a dynamic system with significant implications for life on the surface.
By simulating the movements of BLOBS over the past billion years, the team observed that they produced mantle plumes that were sometimes slightly tilted as they ascended. This resulted in eruptions occurring either directly above or in close proximity to the BLOBS, locations that align with historical eruption records.
"We used statistics to show that the locations of past giant volcanic eruptions are significantly related to the mantle plumes predicted by our models," Cucchiaro and geoscientist Nicholas Flament explained. This consistency with the geologic record provides strong support for their simulations.
Beyond their destructive potential, large eruptions also play a role in creation. Understanding their historical and potential future occurrences could aid in the discovery of valuable magmatic resources, such as kimberlite and diamonds, as well as minerals crucial for renewable energy technologies.
"This research cracks open one of the questions that has long plagued scientists – are the BLOBS stationary or mobile and how do they relate to giant volcanic explosions – so it is a thrill to finally [be able] to unravel these mysteries," Flament concluded.
This groundbreaking research was published in Communications Earth & Environment.
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