Lydia M. Staisch

Coastal uplift of southwestern Washington with implications for deformation caused by crustal faults and the Cascadia subduction​ zone

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High resolution topographic datasets show a flight of flat landforms that increase in elevation along the Willapa Bay, located in southwestern Washington. These landforms are interpreted as wave-cut platforms formed during interglacial periods, when relative sea level was higher than today. Subsequent tectonic uplift has elevated the platforms and preserved them in the landscape. The age and relative elevation of each platform provides the opportunity for investigating the rate of coastal uplift in this region.

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Uplift along southwestern Washington could be caused by permanent inelastic deformation from the Cascadia subduction zone or regional crustal faults. In order to understand the relative importance of each of these potentially major tectonic mechanisms of surface uplift, we are investigating the rate of deformation preserved in wave cut platforms and linking them with potential-field geophysical studies to understand crustal structure. Regional mapping and correlation of wave-cut platforms along the coastline is essential and may give clues into localized versus regional coastal uplift.