Investigation of Lake Quinault in western Washington, including a reflection seismic survey, analysis of piston cores, and preliminary mapping in the steep, landslide-prone Quinault River catchment upstream of the lake, reveals evidence for three episodes of earthquake disturbance in the past 3000 yr. These earthquakes triggered failures on the lake’s underwater slopes and delta front, as well as subaerial landsliding, partial channel blockage, and forced fluvial sediment aggradation. The ages of the three Lake Quinault disturbance events overlap with those of coseismically subsided, coastal marsh soils nearby in southwest Washington that are interpreted to record ruptures of the Cascadia megathrust. Absent from Lake Quinault, however, are signals of obvious disturbance from five additional subduction earthquakes inferred to have occurred during the period of record. The lack of evidence for these events may reflect the limitations of the data set derived from the detrital, river-dominated lake stratigraphy but may also have bearing on debates about segmentation and the distribution of slip along the Cascadia subduction zone during prior earthquakes.

Standing over 2 km above the surrounding topography and flanked by orogen-scale strike-slip faults, the Hangay Dome in central Mongolia is characterized by long wavelength high topography, basaltic eruptions spanning 30 million years, and an abundance of flat-topped summit plateaus. However, despite decades of research, the origin and timing of the intraplate

Sedimentological and geochemical analyses of gravity and piston cores retrieved from Lake Quinault, Washington, reveal an ~4000-year flood-dominated depositional record. Individual flood event layers are identified by combining core stratigraphy, sedimentology, and the ratio of incoherent to coherently scattered x-ray radiation ( inc/coh) from µXRF (x-ray fluorescence) core scans. The inc/coh time series is used as a proxy for sediment grain size and, in combination with radiocarbon-anchored core age–depth models, enables the reconstruction of late-Holocene hydrologic variability for the Quinault River catchment. Decadal to centennial variability in inc/coh is interpreted to reflect trends in ocean-atmosphere teleconnections favorable for the formation of land-falling atmospheric rivers along the Pacific Ocean flank of the Olympic Mountains. Such processes likely modulate the rate of flooding and may explain notable increases in the frequency of flood event layers observed during the periods 2350–2450 cal. yr BP and the most recent century (AD 1910–2010). Understanding past hydrologic variability has important implications for the landscape and ecosystem response of Olympic Mountain catchments to future climate warming.

No abstract