PMC

Failure process of dam overtopping: (a) rise of water level in reservoir area; (b) overflow of dam; (c) discharge of water on slope; (d) scarp erosion; (e) traceability of water; (f) dam failure; (g) dam shrinkage; (h) further erosion; (i) stability phase.

(a) Well-preserved fault scarp of the normal fault bounding the Legemunge playa to the east, showing the nature of the barrier it would present to movement of large animals. This fault causes the eastward tilt of the playa sediments that contain artifacts and fossils and therefore post-dates their deposition. (b) Partly degraded fault scarp southeast of Mt. Olorgesailie subject to first incision and erosion and thus, presumably older than the fault shown in (a). Nevertheless, the fault still acts as barrier to large animal movement. (c) Strongly degraded fault scarp southeast of Mt. Olorgesailie. The intensive erosion affecting the same rock type implies that this scarp is significantly older than the ones shown in (a) and (b), respectively. Photographs by authors.

A) Close-up of the incipient tombolo’s western side and adjacent shoreline (VHR image: ©Maxar [7/11/2019], provided by European Space Imaging). Earlier positions of the eroding backshore scarp are superimposed. Note difference in former scarp positions on the tombolo versus the more stable coastline to the west. B) Excerpt from the Beecheys’ map of Apollonia [], georeferenced and co-registered to a recent VHR satellite image. Red line marks location of the backshore scarp from the 2019 VHR image. Orange and yellow arrows respectively mark locations where extensive and minor coastal change are suggested by the VHR image–historic map comparison.

(a) Airborne LiDAR image showing along-strike continuity of the bedrock scarp (DEM generated from ALS data and co-visualised with slope data calculated using ArcGIS version 10.1 (http://www.esri.com/), (b) field photograph highlighting the sample locality away from areas of Holocene erosion (see also ref. ), (c) and (d) LiDAR topographic profile (plotted using Riscan Pro version 1.2.1 b9 (http://www.riegl.com/products/software-packages/riscan-pro/)), site geometry parameters, fault plane surface roughness and % preservation used in the modelling of the ³⁶Cl data at FIAM (see Methods Summary and ).