Geological controls on large landslides: evidence from the 2024 Wayanad event, India

Document Type

Article

Publication Date

1-1-2026

Abstract

On 30 July 2024, an episode of extreme monsoonal rainfall (~ 572.6 mm in 48 h) triggered a catastrophic landslide in Wayanad, on the eastern flank of the Western Ghats in India. The event resulted in approximately 298 fatalities and 32 persons missing, making it one of the most destructive landslides recorded in this region. The unusual nature of this disaster is reflected in its deep-seated origin, large failure volume, unusually long runout, transport of very large boulders, and extensive geomorphological modification of the landscape. Irrespective of other studies, this highly sheared metamorphic terrain demands an integrated structural and petrographic investigation, with geochemical analyses providing complementary lithological confirmation, to resolve how lithology and deformation architecture govern the high-magnitude landslide dynamics. Field observations indicate that the terrain is underlain by multiple lithologies, including biotite gneiss, garnet–biotite gneiss, charnockite, metagabbro, and granite gneiss. The region has experienced intense ductile shearing followed by brittle deformation, resulting in well-developed foliations parallel to a major E–W-trending shear zone and three principal joint sets (NNW–SSE, NW–SE, and E–W). Analysis of the field data using stereonet projections and rose diagrams, together with geochemical classification based on XRF data, further supports these field observations. Microstructural features such as grain rotation, grain-size reduction, mineral kinking, mica fish, pressure shadows, microfractures, and joints provide additional insights into the intensity of deformation and the tectonic evolution of the region. During extreme rainfall, upstream-dipping joint sets (NE), together with fractures and shear zones, likely facilitated water infiltration and may have promoted localized pore-pressure build-up, whereas downstream-dipping joints (SW) acted as preferential sliding planes. Lithology-dependent deformation and weathering contrasts, combined with the structural framework, control valley confinement, temporary dam formation, the generation and transport of large boulders, deep channel scouring, and high debris mobility were associated with this landslide. The results demonstrate that pre-existing geological and structural conditions contributed to the evolution and destructive behavior of the rainfall-triggered 2024 Wayanad landslide event.

Publication Title

Landslides

Link to Full Text

Share

COinS