Uncovering Earth’s Secrets: Geologists Discover ‘Gigantic Fortresses’ Beneath the Crust in the Mantle

Geologists have discovered massive structures deep within Earth’s mantle, about 1,800 miles down. These formations, known as large low seismic velocity provinces (LLSVPs), are incredibly ancient and sturdier than the cooler oceanic plates surrounding them. Recent seismic studies have shed light on their unique characteristics.

Each “fortress” stretches over an area similar to continents, with one beneath Africa and another under the Pacific. These structures are significantly hotter than the surrounding rock, acting somewhat like islands in a sea of cooler material.

According to Arwen Deuss, a seismologist from Utrecht University, her team conducted research across Europe, Australia, and the U.S. They used seismic waves from major earthquakes to learn about these regions. When a significant quake occurs, the Earth resonates like a bell, and Deuss’s team analyzed the different tones and volumes produced by seismic waves, revealing surprising behaviors.

One key finding is that while these hot regions allow seismic waves to pass through with little loss of energy, the colder areas absorb more energy. This challenges the outdated view that heat alone governs how seismic waves travel through the Earth.

A crucial factor is the size of the crystal grains in the rocks. Over millions of years, the hot regions have larger, more aligned grains, helping energy flow through them efficiently. In contrast, colder areas with smaller grains trap seismic energy more effectively.

Modeling suggests it took over half a billion years for the grains to grow to their current size. This timing indicates that the fortresses likely existed before many supercontinents, including Pangaea, broke apart.

These structures don’t just sit idle; they influence geological processes above. The hot edges of these formations could be the source of magma plumes that lead to volcanic activity, such as the islands of Hawaii. Moreover, they may play a role in worldwide geological events, like mass extinctions linked to volcanic eruptions.

Looking forward, scientists are eager to refine their understanding of these mysterious structures. Researchers plan to enhance monitoring technology and gather more data from seismic events. By comparing volcanic rocks to lab-created samples, they aim to gain insights into the precise nature of the fortresses.

In summary, the discovery of these ancient fortresses below Earth’s surface reshapes our understanding of the planet’s inner workings and their impact on surface geology. This complex interplay remains a vibrant area for ongoing exploration in earth sciences.



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