Missouri Faults and Fossils

Missouri is part of the New Madrid Seismic Zone (NMSZ), which is an active earthquake area. Earthquakes have been shaping the land in the NMSZ for millions of years. Hundreds of earthquakes shake Missouri every year, even though you might not feel them. Earthquakes in this area are produced within a tectonic plate, far from the boundaries between tectonic plates. The earthquakes occur under layers of soft river sediments and sedimentary rock, making them difficult to study. Scientists measured the locations of hundreds of earthquakes to map over 200 kilometers of buried active faults as shown below.

The list below includes information about earthquake activity at the NMSZ. Magnitude is a measurement of the strength of an earthquake.

New Madrid Seismic Zone Earthquake Information

• A 1.0-magnitude earthquake occurs hundreds of times each year.

• A 4.0-magnitude earthquake occurs about every 18 months.

• A 5.0-magnitude earthquake occurs about every 10 years.

• A 6.0-magnitude earthquake occurs about every 80 years.

Compression forces cause earthquakes in the NMSZ in relation to rock layers formed during the Paleozoic and more recent Cretaceous time periods. Fossils of trilobites, corals, and aquatic shelled organisms have been found throughout older Paleozoic rock layers in Missouri. Fossils of dinosaurs, leaves, flowering plants, and marine reptiles have been found in more recent Cretaceous rock layers.