Electromagnetic waves probing the Western Ghats' subsurface.

Decoding Earth's Secrets: What Magnetotelluric Studies Reveal About Western Ghats

Nico Varela in Science & Nature August 2025 • 4 min read.

"Unveiling the Lithospheric Electrical Structure and Tectonic Evolution of India's Western Ghats Region."

The Western Ghats, a stunning mountain range stretching 1500 km along India's west coast, holds secrets to the subcontinent's complex geological history. Its story is tied to the separation of Madagascar, the eruption of the Deccan Traps, and the eventual drifting away of the Seychelles. Understanding this region is crucial for piecing together Earth's dynamic past.

Scientists divide the Western Ghats and its adjacent areas into three distinct zones: the southern zone (Malabar coast), characterized by Precambrian high-grade rocks; the northern zone (Konkan coast), dominated by the Deccan Traps; and the transition zone in between, featuring Precambrian volcano-sedimentary sequences. Geophysical studies, including seismic and gravity surveys, have provided valuable data, but magnetotelluric (MT) studies are now adding another crucial layer of insight.

Magnetotellurics uses naturally occurring electromagnetic fields to probe the Earth's subsurface. By measuring variations in these fields, scientists can map the electrical conductivity of rocks at different depths. This information is invaluable for understanding the composition, temperature, and even the presence of fluids within the Earth's crust and mantle.

Magnetotelluric Studies: Seeing Beneath the Surface

Electromagnetic waves probing the Western Ghats' subsurface.

Several magnetotelluric (MT) studies have been conducted across the Western Ghats, offering a glimpse into the electrical structure beneath this majestic range. These studies reveal a consistent pattern: a two-layered lithosphere. The upper layer is highly resistive, composed of rocks that impede the flow of electricity. Beneath this lies a moderately conductive layer, suggesting materials that allow electrical current to pass more easily.

The depth of the boundary between these two layers varies significantly. In the south, under the Southern Granulite Terrain (SGT), it lies at a depth of 120-160 km. As you move north, towards the Deccan Volcanic Province (DVP), this interface becomes shallower, reaching only 80 km in some areas. This thinning of the resistive layer hints at fundamental differences in the lithospheric structure between the southern and northern parts of the Western Ghats.

Upper High Resistive Layer: Composed of rocks that impede the flow of electricity.
Lower Moderately Conductive Layer: Suggests materials that allow electrical current to pass more easily.
Depth Variation: Ranges from 120-160 km in the south to around 80 km in the north.

One of the most striking findings is the presence of major, near-vertical conductive features associated with the Western Ghats. These features, which cut through the crust, are likely related to the tectonic evolution of the region, possibly linked to faults, shear zones, or fluid pathways. Interestingly, some of these conductive zones are oriented in a northwest-southeast direction, transverse to the compressive stress that dominates the Indian shield. This orientation suggests they may play a role in the region's seismicity.

Implications and Future Directions

Magnetotelluric studies have revolutionized our understanding of the hidden architecture beneath the Western Ghats, shedding light on the processes that shaped this iconic landscape. By integrating MT results with seismic and gravity data, scientists are developing a more complete picture of the Indian lithosphere. These findings have implications for understanding seismicity, resource exploration, and the overall tectonic evolution of the Indian subcontinent. Further research, with denser MT deployments and advanced modeling techniques, will undoubtedly unveil even deeper secrets hidden beneath the Western Ghats.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1007/s12594-018-1062-z, Alternate LINK

Title: Some Insights Into The Lithospheric Electrical Structure In The Western Ghat Region From Magnetotelluric Studies

Subject: Geology

Journal: Journal of the Geological Society of India

Publisher: Springer Science and Business Media LLC

Authors: Prasanta K. Patro, Khasi Raju, S. V. S. Sarma

Published: 2018-11-01

Everything You Need To Know

What key subsurface structures have magnetotelluric studies revealed beneath the Western Ghats?

Magnetotelluric studies have revealed a two-layered lithosphere beneath the Western Ghats. The upper layer is highly resistive, meaning it's composed of rocks that resist the flow of electricity. Below this resistive layer lies a moderately conductive layer, suggesting the presence of materials that allow electrical current to pass more easily. The depth of the boundary between these layers varies, with the interface being deeper (120-160 km) in the south under the Southern Granulite Terrain (SGT) and shallower (around 80 km) in the north, near the Deccan Volcanic Province (DVP).

What are the implications of the near-vertical conductive features discovered within the Western Ghats using magnetotelluric methods?

Major, near-vertical conductive features have been found associated with the Western Ghats. These features cut through the crust and are thought to be related to the region's tectonic evolution. They could be linked to faults, shear zones, or pathways for fluids. The orientation of some of these conductive zones, in a northwest-southeast direction, is transverse to the compressive stress of the Indian shield, potentially indicating a role in the region's seismic activity. Further investigation of these features could illuminate specific fault systems and fluid dynamics influencing earthquakes.

Can you explain the basic principles behind magnetotellurics and how it helps in studying the Earth's subsurface, especially in areas like the Western Ghats?

Magnetotellurics, or MT, is a geophysical method that uses naturally occurring electromagnetic fields to investigate the Earth's subsurface. By measuring variations in these fields at the surface, scientists can map the electrical conductivity of rocks at different depths. This provides valuable information about the composition, temperature, and fluid content of the Earth's crust and mantle. Unlike seismic or gravity surveys, magnetotellurics is particularly sensitive to the presence of conductive materials, such as fluids or interconnected mineral grains, offering unique insights into subsurface processes.

What do the depth variations in the resistive layer beneath the Western Ghats signify about the region's geological composition and history?

Variations in the depth of the resistive layer's base, the boundary between the upper resistive and lower conductive layers, suggest differences in the lithospheric structure between the southern and northern parts of the Western Ghats. The resistive layer is deeper in the south, under the Southern Granulite Terrain (SGT) at 120-160 km, and shallower in the north, towards the Deccan Volcanic Province (DVP) at around 80 km. This thinning could be related to thermal variations, compositional differences, or past tectonic events that have differentially affected the lithosphere in these regions. Detailed analysis of these depth variations could help reconstruct the tectonic history of the Western Ghats.

How are magnetotelluric findings integrated with other geophysical data to provide a more comprehensive understanding of the Indian lithosphere and its evolution?

Combining magnetotelluric results with other geophysical data, such as seismic and gravity data, allows scientists to develop a more comprehensive understanding of the Indian lithosphere. This integration can help to better constrain subsurface structures, identify potential seismic hazards, and understand the regional tectonic evolution. For example, integrating MT-derived conductivity models with seismic velocity models can help to distinguish between different rock types and identify fluid-filled zones. Furthermore, combining these datasets with geological mapping and geochemical analyses can provide a holistic view of the processes that have shaped the Western Ghats and the broader Indian subcontinent.