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Glacial retreat in recent decades has exposed unstable slopes and allowed deep water to extend beneath some of those slopes. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever documented worldwide. Precursory deformation began decades before failure, and the event left a distinct sedimentary record, showing that geologic evidence can help understand past occurrences of similar events, and might provide forewarning. The event was detected within hours through automated seismological techniques, which also estimated the mass and direction of the slide - all of which were later confirmed by remote sensing. Our field observations provide a benchmark for modeling landslide and tsunami hazards. Inverse and forward modeling can provide the framework of a detailed understanding of the geologic and hazards implications of similar events. Our results call attention to an indirect effect of climate change that is increasing the frequency and magnitude of natural hazards near glaciated mountains.

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The Mw 7.1 Darfield (Canterbury) earthquake of 4 September 2010 (NZST) was the first earthquake in New Zealand to produce ground-surface fault rupture since the 1987 Edgecumbe earthquake. Surface rupture of the previously unrecognised Greendale Fault during the Darfield earthquake extends for at least 29.5 km and comprises an en echelon series of east-west striking, left-stepping traces. Displacement is predominantly dextral strike-slip, averaging ~2.5 m, with maxima of ~5 m along the central part of the rupture. Maximum vertical displacement is ~1.5 m, but generally < 0.75 m. The south side of the fault has been uplifted relative to the north for ~80% of the rupture length, except at the eastern end where the north side is up. The zone of surface rupture deformation ranges in width from ~30 to 300 m, and comprises discrete shears, localised bulges and, primarily, horizontal dextral flexure. At least a dozen buildings were affected by surface rupture, but none collapsed, largely because most of the buildings were relatively flexible and robust timber-framed structures and because deformation was distributed over tens to hundreds of metres width. Many linear features, such as roads, fences, power lines, and irrigation ditches were offset or deformed by fault rupture, providing markers for accurate determinations of displacement.

Quantifying how hillslopes respond to river incision and climate change is fundamental to understanding the evolution of uplifting landscapes during glacial-interglacial cycles. We investigated the interplay among uplift, river incision, and hillslope response in the nonglacial Waipaoa River catchment located in the exhumed inner forearc of an active subduction margin on the East Coast of the North Island of New Zealand. New high-resolution topographic data sets (light detection and ranging [lidar] and photogrammetry) combined with fi eld mapping and tephrochronology indicate that hillslopes adjusted to rapid latest Pleistocene and Holocene river incision through the initiation and reactivation of deep-seated landslides. In the erodible marine sedimentary rocks of the Waipaoa sedimentary system, postincision deep-seated landslides can occupy over 30% of the surface area. The ages of tephra cover beds identifi ed by electron microprobe analysis on 80 tephra samples from 173 soil test pits and 64 soil auger sites show that 4000-5000 yr after the initiation of river incision, widespread hillslope adjustment started between the deposition of the ca. 14,000 cal. yr B.P. Waiohau Tephra and the ca. 9420 cal. yr B.P. Rotoma Tephra. Tephrochronology and geomorphic mapping analysis indicate that river incision and deep-seated landslide slope adjustment were synchronous between main-stem rivers and headwater tributaries. Hillslope response in the catchment can include the entire slope, measured from river to ridgeline, and, in some cases, the interfl uves between incising subcatchments have been dramatically modified through ridgeline retreat and/or lowering. Using the results of our landform tephrochronology and geomorphic mapping, we derive a conceptual time series of hillslope response to uplift and climate change-induced river incision over the last glacial-interglacial cycle. Cretaceous to Early Tertiary interbedded mud and sandstoneMajor rivers and streams 1 10 0 0) ) ) W W Wa a ai i it t ta a an n ng g gi i i 1 11 1 1) ) ) U 1 18 8 8) ) ) W W Wh h ha a ar r re e ek k ko o op p pa a ae e e 1 19 9 9) ) ) T T To o ot t ta a an n ng g gi i i 2 20 0 0) ) ) W W Wa a ai i ik k ka a ak k ka a ar r ri i ik k ki i i 2 21 1 1) ) ) T T Te e e A A Ar r ra a ai i i 1 1) ) ) W W Wa a ai i ip p pa a ao o oa a a 2 2) ) ) W W Wa a ai i im m ma a at t ta a a 3 3) ) ) N N Ng g ga a ak k ko o or r ro o oa a a 4 4) ) ) U U Ur r ru u ut t ta a ar r ra a an n ng g ga a a 5 5) ) ) M M Ma a an n ng g ga a ao o oa a ai i i 6 6) ) ) W W Wa a ai i ih h ho o or r ra a a 7 7) ) ) W W Wa a ai i in n ng g ga a ar r ro o om m mi i ia a a 8 8) ) ) U Up p pp p pe e er r r W W Wa a ai i ip p pa a ao o oa a a 1 12 2 2) ) ) M M Ma a an n ng g ga a at t tu u u 1 13 3 3) ) ) M M Ma a an n ng g ga a am m ma a ai i ia a a 1 14 4 4) ) ) M M Ma a an n ng g ga a ap p pa a ap p pa a a 1 15 5 5) ) ) U U Ur r ru u uk k ko o ok k ko o om m mu u uk k ka a a 1 16 6 6) ) ) W W Wa a ai i ik k ka a ah h hu u u 1 17 7 7) ) ) W W Wa a ai i ih h hu u uk k ka a a