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Flights of Holocene marine terraces are useful for reconstructing past earthquakes, but coastal erosion can remove terraces from the landscape, potentially leading to incorrect estimates of earthquake magnitude and frequency. Relatively little effort has been afforded to studying terrace erosion processes, and this paper presents the first field evidence that we are aware of documenting terrace erosion rates. Two case studies from New Zealand provide a unique opportunity to observe the beginning and end phases of terrace development. We present downwear and backwear erosion measurements, showing that both sets of processes are important. Micro‐erosion meter measurements from Kaikōura Peninsula, South Island, confirm that downwear processes are modifying new marine terraces that were created when the peninsula was uplifted about 1 m during the 2016 earthquake. Erosion rates were high immediately following uplift as the relatively barren intertidal rock shore platform rapidly transformed into an incipient marine terrace with cover deposits. However, the Kaikōura earthquake uplifted shore platforms only a small distance above the upper tidal limit and ongoing downwear and backwear erosion may begin to remove parts of this terrace in future decades. We explored this prospect with a case study at Māhia Peninsula, North Island, where 100–300 years have elapsed since the last terrace‐forming earthquake. Historical photographs were used to document about 80 years of backwear erosion. Terrace erosion rates have been nearly constant through this period, and extrapolation implies that the terrace will be removed in places by 2030. The erosion data in this paper provide new insights into how terraces can be removed from the landscape, but there are many complicating factors. To help understand these factors we present a new conceptual model of marine terrace creation and destruction for soft‐rock coasts. [ABSTRACT FROM AUTHOR]

Holocene marine terraces occur globally and record information about the timing and magnitude of past coseismic events. Staircased terraces develop through repetitive coseismic uplift of shore platforms, but are also subject to destruction from subsequent wave erosion and rock weathering. In this study we calibrate a rock coast evolution model using terrace field data from Mahia Peninsula, New Zealand, and use it to investigate how relative sea level (RSL) change influences Holocene terrace development. Analyses of 10,002 simulations reveal time periods of extremely rapid terrace creation and destruction as a result of shore platform development processes that are modulated both by episodic and gradual RSL change scenarios. Subtle differences in these scenarios give rise to completely different terrace sequences, even if coseismic event timing is held constant. Improved interpretation of Holocene terrace sequences require higher resolution paleo RSL data and chronological data on shore platform development. Plain Language Summary: Holocene marine terraces develop when tectonically active rock coasts are uplifted during earthquakes, and thus provide the information about the timing and magnitude of past seismic events that is useful to estimate future seismic hazards. However, the record is often partial because once terraces are uplifted, subsequent marine erosion processes (wave erosion and intertidal rock weathering) start destroying terraces and can completely remove them from the landscape. This can confound paleo‐seismic interpretations of Holocene terrace sequences. In this study we used a numerical model to explore how earthquake‐driven episodic and climate‐driven gradual relative sea level (RSL) changes can influence marine erosion processes, and therefore Holocene terrace preservation. The simulation results reveal that subtle differences in episodic and gradual RSL change histories can lead to periods in which marine erosion are greatly accelerated, which can completely alter terrace sequences that are preserved in the landscape. Until this study, we had little understanding of the way in which RSL modulates the erosion processes that control terrace creation and destruction. We conclude that better interpretation of past seismic event history from Holocene terraces require a more detailed understanding of RSL history and higher resolution data on rates of shore platform formation through time. Key Points: The effects of episodic and gradual relative sea level (RSL) change on Holocene marine terrace development are numerically exploredEven subtle differences in RSL have large impacts on shore platform development rates, thereby changing preserved terrace sequencesBetter understanding of past RSL and shore platform development history will improve paleo‐seismic interpretation of Holocene terraces [ABSTRACT FROM AUTHOR]