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Himalayas unperturbed

Words by Sade Agard
1 March 2022

The erosion and weathering of mountain ranges make these geologically complex systems home to multiple carbon sources and sinks. In particular, silicate mineral weathering (coupled with carbonate precipitation in the oceans), as well as the erosion, transport and burial of organic carbon along continental margins are major carbon sinks that play a key role in the long-term evolution of global climate. However, it is difficult to define the net-carbon budget for a mountain range linked to erosion at climatically relevant timescales because the erosional processes, which are dominated by earthquakes and landslides, are somewhat random in nature.

Lena Märki at ETH Zurich, Switzerland, and colleagues calculate the carbon budget for erosion in the Narayani catchment of the central Himalaya in response to the 2015 Mw 7.8 Gorkha earthquake – an event that caused more than 25,000 landslides in the Central Himalaya. The team use a high-resolution time series to quantify the evolution of the inorganic and organic carbon fluxes linked to erosion during four monsoon seasons before and after the earthquake. The data show that while erosion in the central Himalaya acts as a net carbon sink, largely due to the efficient export of organic carbon, the Gorkha earthquake did not significantly shift the long-term carbon flux in the region.

The authors draw comparisons with the 2008 Mw 7.9 Wenchuan earthquake, an event that is thought to have affected the net-carbon budget for the catchment. The volume of material mobilised by landslides during the Wenchuan earthquake was substantially larger than that liberated by the Gorkha earthquake. Thus, the authors conclude that the relative frequency of large earthquakes in the central Himalaya has created a landscape that is in quasi-equilibrium, meaning that the short-term carbon budget for this region is relevant on interglacial timescales, too.

  Nat. Geosci. 14, 745–750 (2021); doi.org/10.1038/s41561-021-00815-z

Sade Agard
Sade Agard is a graduate geologist and Chair of the Area Code Foundation, a not-for-profit resource management organisation working in Bambilor, Senegal

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