multaneously record. Because marine strandlines are the physical records of past sea levels, the study of sea-level history is an integral part of coastal tectonics.
Time-transgressive sequences of displaced and deformed Pleistocene [2 m.y. to 10,000 yr (10 ka) ago] marine strandlines document patterns of and, where dated, yield rates of continual, long-term crustal deformation (Figures 6.1 and 6.2). Sequences of emergent Holocene (past 10 ka) strandlines (Figure 6.3), which occur only along the most rapidly uplifting coastlines, commonly record abrupt coseismic uplift events of 1–15 m (see Figures 6.25–6.28 below) that cumulatively comprise the long-term deformation recorded by Pleistocene strandlines. Consequently, sequences of Holocene strandlines often record past earthquakes and, where dated, yield earthquake periodicity and provide a means of forecasting future seismic events. In many areas, apparent sea-level changes documented by tide-gauge records (Figure 6.4) or subtle shifts in the location of the modern shoreline reflect ongoing vertical crustal movement. Frequently, this movement is opposite in sense to long-term trends and, therefore, may represent postearthquake crustal relaxation or pre-earthquake strain accumulation.
Coastal tectonics includes the study of both onshore (emergent) and offshore (submergent) marine strandlines and structural features. However, offshore coastal tectonics is a highly specialized field and is beyond the scope of this brief review, which focuses mainly on the formation and deformation of emergent marine strandlines and stresses their importance in determining the style and measuring the rates of recent crustal deformation, especially in highly active coastal regions. Most examples of strandline displacement and deformation cited in this review reflect sustained tectonic processes, but a few, included mainly for comparative purposes, reflect transitory volcanic and glacio-isostatic crustal deformation.
On global and regional scales coastal morphology correlates closely with tectonic setting (Inman and Nordstrom, 1971). The greatest geomorphic contrast is between the subdued coastlines along passive continental margins and the rugged coastlines along convergent plate boundaries. Along most coastlines modern (active) coastal landforms are similar to their Pleistocene counterparts, which suggests that current tectonic and coastal processes have been fairly uniform over considerable periods of time.
Most exposed coastlines along passive continental