This EarthCache is just off Interstate 65 and directly under the Cumberland Science Museum. Since we cannot get to it directly, we must view it from across the interstate. Park near the posted coordinates and walk to the fence bordering I-65.
Look carefully at the rock face. The stratum exposed here is the Bigby-Cannon Formation of the middle Ordovician Nashville Group. During the deposition of this formation, the water over Nashville alternated between periods when it was sheltered by a reef and periods when it was exposed to the open ocean. The light bands represent periods when the water was sheltered.
Note the diagonal fissure in the rock face - this is a fault. Faults form when sections of the earth's crust are moving toward one another (compression) are moving away from one another (extention) are moving past one another
To Log this cache: Click the USGS link below and Take a look at the explanation of faults on this and determine the type of deformation and type of stress for this fault and email the answer. So when did this earthquake occur?
The fact that the strata have remained intact, with a clean break at the fault indicates that the sediment had turned to rock (lithified) before the earthquake occurred. Therefore the earthquake must have occurred a good while after the middle Ordovician period.
The Cumberland Science Museum, located directly above this fault is not in any danger. Now all faults are active. Geologists define an active fault as one which has moved in the past 10,000 years. Most active faults in Tennessee produced earthquakes in along the Mississippi River or in the eastern section of the state.
If you are interested in the USGS's record of seismic activity for the state of Tennessee check out this link: https://www.usgs.gov/faqs/what-a-fault-and-what-are-different-types#
