A great escarpment is characterized with extremely asymmetrical topography with a steep and high-relief mountain range rimming a low-relief high plateau. Measured erosion rates contradict the observed high relief of the escarpments of Madagascar and India. We used cosmogenic nuclide (CN) ¹⁰Be concentrations to infer horizontal retreat rates of escarpments. Million-year scale retreat rates of Madagascar and India escarpments are ~1 km/Ma. CN ¹⁰Be-inferred retreat rates and escarpment morphology are consistent with steady retreating escarpment from modern coastlines since rifting for both margins.

The edge of the escarpment usually acts as the water divide. Previous studies conceptualize an escarpment as a migrating water divide. We studied the morphological features the escarpment and continental water divide of Madagascar and India, demonstrating that the continental water divide does not universally correspond to the steep rift escarpment due to river captures. We hypothesized that the heavily weathered plateau encourages frequent river capture and affects the morphology and rates of escarpment retreat.

We used 2D landscape evolution models to explore factors in controlling escarpment retreat. Model observations support the hypothesis that divide migration patterns control escarpment retreat patterns through the control of captured drainage area from the plateau. Through frequent river capture or divide advance into an erosional weak layer, rivers increase area and thereby increase the retreat rate. Measured escarpment retreat rates of eastern Madagascar and Western Ghats, India support this model and quantify the effect of captured area on escarpment retreat rate.

Major strike-slip fault systems on Earth, like the North Anatolian Fault (NAF), play an important role in accommodating plate motion, but little is known about their spatiotemporal evolution. In the Central Pontides, north of the central segment of the NAF, data from thermochronology suggest an exhumation phase occurred after 11 Myr. However, the precise onset of this uplift phase is poorly constrained. In this study, we define the spatiotemporal rock-uplift pattern within the Central Pontides over the last ~10 Myr by performing linear inversions of 19 river profiles draining the northern margin of the Central Pontides, from the Sinop Range to the Black Sea. We use 21 new ¹⁰Be-derived basin-average denudation rates to calibrate an erodibility parameter, necessary to infer rock-uplift histories from χ-transformed river profiles. Our results document an increase in rock-uplift rates after 10 Ma, with peaks of 0.15–0.25 km/Myr occurring between 4 and 2 Ma. Moreover, the spatiotemporal uplift variations suggest that rock uplift migrated westward over a period of 2–2.5 Myr. Linking the uplift to the transpression produced along the NAF central segment, we used the faster uplift onset to calculate the NAF propagation rate, estimated to be ~74±13 km/Myr. Combining our results with those from previous studies on the NAF age, we found differences in fault-propagation rates that coincide with differences in the orientation of the NAF relative to plate-convergence vectors. Fault segments with higher obliquity appear to have propagated at rates up to 2-fold slower than those oriented parallel to the plate-convergence vector.

The Cenozoic uplift of the Tibetan Plateau leads to eastward lateral extrusion of fault-bounded blocks, which caused large surface uplift. To the northeast of the Tibetan Plateau, the development of the particular fluvial incision landscape on the internally stable Ordos Loess Plateau reflects the lateral extrusion and thrust loading by the adjacent Liupanshan Mts. in the west. In this study, we investigated the climate-mediated temporal evolution of surface uplift and the effect of activity along confining faults on the morphological evolution of the Ordos Loess Plateau by fieldwork, morphological analysis and integration of results from numerous previous studies. Field surveys show that the boundaries of the Ordos Loess Plateau are still tectonically active and fluvial channels are in a state of morphological disequilibrium, with steep channel segments towards the Weihe Graben and meandering low-gradient rivers in the central Ordos Loess Plateau. Morphological analysis shows that the shape of the longitudinal channel profile is straight and deviates from typical longitudinal channel profiles and the degree of erosion and plateau incision is more pronounced in the southeastern Ordos Loess Plateau. We conclude that the northeastern expansion of the Tibetan Plateau activated the boundary faults around the tectonically stable, craton-like Ordos Loess Plateau, which caused the drainage basins to tilt towards the overthrusting Liupanshan Mts in the southwest. The drainage systems reorganized to a principal southern flow direction towards the Weihe Graben caused by the ongoing E-W shortening and ca. N-S extension and thereby progressively incising in the Ordos Loess Plateau.

Islands are interesting geomorphic features because they possess a well defined base level. Non-volcanic islands, in particular, are the product of rifting of a small continental fragment such that they start their geomorphic evolution as a more or less elevated flat plateau. After tens of millions of years of evolution, some islands, such as Madagascar, still present a Pi-shaped form composed of large watersheds on top of a central plateau surrounded by smaller ones that connect the plateau to the coastline. Other islands, such as Sri Lanka have a more conical or Lambda-shape composed of a radial distribution of basins connecting the island summit to the coastline. Here we investigate the conditions that lead to the transformation of an initially plateau-shape island to either a Pi- or Lambda-shape by using a Landscape Evolution Model solving the Stream Power Law and talking into account flexural isostasy.

We find that to maintain a Pi-shape, an island must fulfil two criteria: firstly, its extent must be sufficiently large in comparison with the underlying effective elastic thickness (EET), and, secondly, it must be subjected to limited erosion. We introduce a morphometric index that allows to discriminate between the two types of morphologies and show how it evolves through time as a function of both EET and erodibility.

Constraining the time evolution of the morphology of an island is important to study the evolution of its bio-diversity. Our finding implies that the micro-endemism that characterises Madagascar is linked to the strength of the underlying lithosphere.

Large magnitude (Mw ∼ ≥6) earthquakes in extensional settings are often associated with simultaneous rupture of multiple normal faults as a result of static and/or dynamic stress transfer.
Here, we report details of the coseismic breaching of a previously unrecognized large-scale fault relay zone in central Greece, through three successive normal fault earthquakes of moderate magnitude (Mw 5.7–6.3) that occurred over a period of ∼10 days in March 2021. Specifically, joint analysis of InSAR, GNSS and seismological data, coupled with detailed field and digital fault mapping, reveals that the Tyrnavos Earthquake Sequence (TES) was accommodated at the northern end of a ∼100 km wide transfer structure, by faults largely unbroken during the Holocene. By contrast, the southern section of this relay zone appears to have accrued significant slip during Holocene. InSAR-derived displacements agree with the loci of eight subtle, previously undetected, faults that accommodated coseismic and/or syn-seismic normal fault slip during the TES. Kinematic modeling coupled with fault mapping suggests that all involved faults are interconnected at depth, with their conjugate fault-intersections acting largely as barriers to coseismic rupture propagation. We also find that the TES mainshocks were characterized by unusually high (>6 MPa) stress-drop values that scale inversely with rupture length and earthquake magnitude. These findings, collectively suggest that the TES propagated northwestward to rupture increasingly stronger asperities at fault intersections, transferring slip between the tips of a well-established, but previously unrecognized, relay structure. Fault relay zones may be prone to high stress-drop earthquakes and associated elevated seismic hazard.