Long-term patterns of hillslope erosion by earthquake-induced landslides shape mountain landscapes

Abstract

Widespread triggering of landslides by large storms or earthquakes is a dominant mechanism of erosion in mountain landscapes. If landslides occur repeatedly in particular locations within a mountain range, then they will dominate the landscape evolution of that section and could leave a fingerprint in the topography. Here, we track erosion provenance using a novel combination of the isotopic and molecular composition of organic matter deposited in Lake Paringa, New Zealand. We find that the erosion provenance has shifted markedly after four large earthquakes over 1000 years. Postseismic periods eroded organic matter from a median elevation of 722 +329/−293 m and supplied 43% of the sediment in the core, while interseismic periods sourced from lower elevations (459 +256/−226 m). These results are the first demonstration that repeated large earthquakes can consistently focus erosion at high elevations, while interseismic periods appear less effective at modifying the highest parts of the topography.

Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

“…Further, only the largest (10-year return or more) floods will transport substantial parts of the deposit, meaning that large landslide events may load channels with a pulse of coarse sediments that require several decades to be evacuated. This is much longer than the transient pulse of enhanced landsliding (Marc et al, 2015) and suspended sediment transport (Hovius et al, 2011) observed after the Chi-Chi earthquake, which lasted less than 10 years, but is consistent with the ∼ 50-year timescales for enhanced lake sediment deposition (including bed load) after earthquakes observed in New Zealand (Howarth et al, 2012;Wang et al, 2020). This multidecadal timescale for sediment export seems consistent with the very large alluviation of river channels in southern Taiwan following intense flooding and landsliding triggered by Typhoon Morakot (Yanites et al, 2018), which was still visible in 2015 (e.g., Taimali River) and at the time of writing in satellite imagery.…”

“…In those settings, understanding and modeling the controls on the landslide GSD should be an urgent goal, although, to date, it has only been addressed by a few studies. Indeed, in contrast to river sediments, for which many studies exist (e.g., Ibbeken, 1983;Whittaker et al, 2011;Chung and Chang, 2013;Guerit et al, 2014Guerit et al, , 2018, landslide GSDs have rarely been measured; this is, in part, because the latter is considerably more difficult, time consuming and potentially dangerous than the former.…”

Organic Molecular Paleohypsometry: A New Approach to Quantifying Paleotopography and Paleorelief

“…Studies from a range of landscapes show downslope transport of biomarkers can bias geochemical signatures preserved in low elevation sites yet interpreting these data may be complicated. For example, storm and mass wasting events are shown to produce greater mobilization of materials from the steep proportions of a catchment (Wang et al, 2020). While organic molecular paleohypsometry has the potential to provide a means of quantifying changes in the elevation distribution of biomass within an orogen, reliable application of such an approach to ancient sediments requires constraints on several variables.…”

Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model

“…In this study, we introduce a reduced-complexity modeling approach to quantify the fate of OC eroded from soils after a widespread landslide-triggering event, such as a major earthquake. This is also relevant to better understand how organic matter may provide a novel tool of erosion provenance in sedimentary records (Wang et al, 2020). Our aim is to explore the climatic, tectonic and biogeochemical controls on the fate of OC over decadal to centennial timescales.…”