THE ADVANCE LATERAL SPREAD, A MASSIVE AND POTENTIALLY SEISMICALLY INDUCED FEATURE IN SOUTHEAST MISSOURI

The Advance Lateral Spread is a 67 square kilometer feature located just east of the town of Advance, in southeastern Missouri. The areal extent of the feature suggests that it may be one of the largest lateral spreads in the world. It is located within the upper Mississippi Embayment in the Bell City Gap of Crowley’s Ridge just east of a massive late Pleistocene Mississippi River crevasse splay feature. The feature is located within 50 km of 3 of at least 6 segments comprising the New Madrid Seismic Zone and lies just 16 km NW of the Commerce Geophysical Lineament (Commerce Fault), which is named for nearby Commerce, Mo. It was identified as a lateral spread through its geomorphic expression, which includes a striking arcuate headscarp, numerous subsidiary scarps within the translated mass, disrupted surface drainage, and roughly fan-shaped nature. The arcuate scarp is approximately five meters high and has previously been interpreted as a Pleistocene cutbank of the Mississippi River that was formed subsequent to the aforementioned crevasse splay or as of lacustrine origin. Another diagnostic feature is the apparent hydraulic choking and diversion of the Whitewater River, which traverses the entire toe of the feature. The spread appears to have translated approximately 1.6 km at its maximum extent and the river appears to have been deflected to the east by a similar distance. There is a large secondary scarp developed within the spread, which suggests that the feature may have reactivated on at least one occasion.

The choking of the Whitewater River occurs within easily erodible Pleistocene alluvium and loess, and the sharp geomorphic features suggest that the spread was likely triggered by the geologically recent event, possibly the 1811-12 earthquake sequence in the New Madrid Seismic Zone. The surface of the feature has been utilized for agricultural purposes and several of its scarps have conveniently been turned into irrigation and drainage ditches.