Unveiling Earth's Subterranean Secrets: The 'Dripping' Crust Beneath Turkey
The Earth's crust is not always as solid and stable as it seems. Beneath the Central Anatolian Plateau of Turkey, a captivating geological phenomenon unfolds, revealing a crust that is 'dripping' downwards. This intriguing discovery has captivated scientists, prompting them to delve deeper into the underlying causes.
The Konya Basin, a distinct feature within the Central Anatolian Plateau, showcases a clear pattern of subsidence. Despite the surrounding plateau's rise over geological time, the basin continues to deepen. This phenomenon raises the question: How can a region that is generally rising also have a central area that sinks, resembling a shallow dent in a flat tabletop?
A team of earth scientists at the University of Toronto, led by Julia Andersen, embarked on a mission to unravel this mystery. They combined satellite measurements with various Earth data to study the crust and upper mantle beneath the Central Anatolian Plateau.
The Konya Basin stood out due to its bowl-shaped structure, contrasting with the surrounding plateau. Satellites and seismic waves played a crucial role in this investigation. Satellite tools can detect subtle ground changes over vast areas, while seismic waves from earthquakes provide insights into the planet's inner layers by varying wave speeds in different materials.
Andersen and her team observed a significant finding: a circular feature in the Konya Basin where the crust is subsiding. This led them to analyze other geophysical data, revealing a seismic anomaly in the upper mantle and a thickened crust. These indicators suggested the presence of high-density material, pointing to a 'mantle lithospheric drip'.
The study, published in Nature Communications, introduces the concept of multi-stage lithospheric dripping. This process occurs when parts of the lower lithosphere become unusually dense, causing gravity to pull the heavy material downward until it separates and sinks into the mantle. This sinking disrupts the balance of forces in the rock column, leading to surface sagging and the formation of a basin.
Over time, if the dense material detaches and sinks further, the surface can rebound and rise, no longer burdened by the extra weight. According to past studies, the Central Anatolian Plateau has risen by approximately 0.6 miles over the last 10 million years, driven by this unique process.
Russell Pysklywec, a co-author of the study, explains, 'As the lithosphere thickened and dripped below the region, it formed a basin at the surface. Later, when the weight below broke off and sank into the deeper mantle, the surface sprang back up.' This process is not a one-time event but seems to initiate subsequent geological events in the region, resulting in the rapid subsidence of the Konya Basin within the rising plateau of Turkey.
To validate their theory, the researchers created lab models that mimicked the deep Earth's behavior in slow motion. They used a plexiglass tank filled with a silicone polymer fluid to represent the lower mantle, added a mix of fluid and clay for the uppermost solid mantle, and topped it with a ceramic and silica sphere layer to simulate the crust.
While these materials don't perfectly replicate Earth's crust, they provide valuable insights into the formation and growth of instabilities. When a dense part sags and detaches in the model, it offers a plausible explanation for how a real lithosphere might undergo similar changes over millions of years.
Andersen concludes, 'Our findings indicate that these significant tectonic events are interconnected. One lithospheric drip can potentially trigger a series of activities deep within the planet.'
The study's implications extend beyond Earth. By comparing the findings with the Arizaro Basin in the Andes of South America, the team suggests that this process is not limited to a single country or plateau. Mountain plateaus, with their thick crust, deep heat, and complex stresses, create conditions conducive to the formation of dense lower layers, which can start sinking.
This research also has implications for understanding other worlds. Mars and Venus, for instance, do not follow Earth's plate tectonic system, yet their interiors still move heat and redistribute dense and light materials. The concept of dense rock peeling off and sinking without a plate boundary's influence provides planetary scientists with an alternative explanation for significant surface features on planets with different tectonic rules.
The full study, published in Nature Communications, offers a fascinating glimpse into the subterranean dynamics of our planet and beyond.
