Our first site is on Interstate 40 directly under the Cumberland Science Museum.  We cannot get to it directly, so we must look at it from across the interstate.

Directions:

• Starting in the center of the city, drive south on 8th Avenue.
• After going under I-40, turn left at the first street.
• Park 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.  Simplified into a diagram, the exposure looks like this.

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

When do you think the earthquake occurred?

Did it occur at the same time that the sediment was being deposited (middle Ordovician) or later?
How can you tell?

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.
 

Finally, consider the Cumberland Science Museum, located directly above this fault.  Is the museum in any danger?  Can we be sure that this fault is not active?  How would we check it out?

Now all faults are active.  Geologists define an active fault as one which has moved in the past 10,000 years.  To get an idea where active faults are, we can look at the USGS's record of seismic activity for the state of Tennessee.  As you can see, virtually all earthquakes in Tennessee occur either along the Mississippi River or in the east.