Steep slopes, weak rock types combine with human activities to hasten landslides

The Great Escarpment separates the lowlands of western India from the highlands. In this region, the highest levels of precipitation—over 2,000 mm per year—occur in the lowlands, while precipitation decreases to 500-1,000 mm per year not far away in the highlands. Additionally, monsoons occur partly because the interior of continental landmasses heats up, a process influenced by the altitude of plateaus. These simple examples demonstrate that both escarpments and plateaus have a fundamental impact on weather dynamics. However, it is difficult to disentangle their effects on monsoon dynamics, as monsoons are also influenced by other climatic factors, such as orbital forcing (how the Earth’s orbit changes through time, and influences the amount of incoming radiation from the sun).

Yes, my team is also currently working on the continental rifting in the Afar Region (North-Eastern Ethiopia) and the East African Rift. It is conceivable that, one day, the small continental fragment that separates could collide with the western coast of India. However, even if this were to occur—an outcome that depends on various global factors—it would likely not happen for hundreds of millions of years.

One implication of our model is that continental surfaces, such as the Western Ghats, are more dynamic than previously thought. Earlier research generally linked uplift to a narrow time window during the rifting, or stretching, of the continent. Our findings, however, show that the uplift process takes much longer, as the driving force within the mantle migrates over time. We need to collect more data from the continental interior region to establish when the latest uplift and erosion occurred.

Our computer models aim to simulate how the Earth’s uppermost layers respond to being stretched by tectonic forces, such as plate movements. To construct these models, we consider the densities of different layers and how they might strain as they deform. Our simulations indicate that once a rift forms—like the ancient Madagascar-India rift that separated those landmasses around 82 million years ago—it thins the crust, allowing hot mantle rock below to rise. As this hot mantle rises, it cools when it interacts with the surrounding cooler crust. This cooling increases the mantle’s density, causing it to sink. The combination of upwelling and sinking generates a type of circulation known as “edge-driven convection”. This process disturbs nearby continental roots, leading to a chain of similar convective instabilities that migrate inland along the continent’s deep root over time.