Fifty Years of Shore Platform Erosion Monitoring at Kaikōura Peninsula, South Island, Aotearoa-New Zealand

The shore platforms around Kaikōura Peninsula, located on the tectonically active east coast of South Island, Aotearoa New Zealand, host the world’s longest-running erosion monitoring record. Since 1973, a network of micro-erosion meter (MEM) stations has been used to measure downwearing across mudstone and limestone platforms to explore processes responsible for and the rate of development of the shore platforms. Here, we review and report on five decades of observations, assess spatial and temporal patterns of erosion and evaluate the consistency of downwearing rates. Although never originally intended as part of the programme, we can now quantify the geomorphic response to one metre of coseismic uplift associated with the 2016 M_w 7.8 Kaikōura earthquake. Pre-earthquake erosion rates averaged 1.00 mm/yr (STDV = 0.73) across 9 measurement epochs. Post-earthquake rates more than doubled to 2.54 mm yr^-1 reflecting enhanced subaerial weathering on the uplifted surfaces. Limestone platforms tended to erode more slowly (1.30 mm/yr) than mudstone (3.27 mm/yr), a significant difference between the two rock types that had not been evident before the 2016 uplift. Seasonal differences in erosion with higher rates in summer than winter observed prior to the earthquake remained pronounced after 2016 but the subaerial processes responsible have likely changed. These findings highlight the critical role of changing processes, the geomorphic significance of tectonic events on rock coasts, and the pathway from shore platform to marine terrace generation. The Kaikōura dataset provides a reference for interpreting short- and long-term erosion dynamics and highlights the scientific legacy of the late Emeritus Professor R.M. (Bob) Kirk.