Can you imagine the precision it would take to blast a tunnel through this solid quartzite block? This tunnel was constructed during the winter of 1951. Experts drilled shot holes to be used for the charges of dynamite. They had to be very careful while drilling and blasting because this chunk of rock has many fault lines. A fault is a break in the earth's crust along which blocks of rock slip past one another. If you look closely between the two blocks of rock you will see that the fault has ground the rock into sand. Geologists call this fault breccia. Faults like this are the paths that water followed to create the caves. Further up the trail you will see additional evidence of faulting.

The above picture looks back through the first tunnel where a small fault is visible on the left hand wall. This is the same fault which is discussed above. A closer view of this fault can be seen below, the white line which defines this fault is actually fine sand.

You are now ¼ of the way there!

Now let's look west just past the tunnel for another view of the American Fork Canyon. Notice the slanted cracks which appear in the rock on the north (right) side of the photograph. These slanted "cracks," however are not faults. These are actually bedding planes, separations between material that settled onto the botton of the ancient tropocal sea where these deposits first accumulated. These beds of rock which are now slanted were once flat but the same tectonic forces that eventually caused faults to form first bent and tilted these rock beds into their current position.