I found this rock by the Delaware river on a hike for Geology 100. There is a line in the rock that almost looks like it’s splitting apart. This line is called a tension gash and is filled with crystal. This small rock gives us hints into the history of the Delaware river millions of years ago. Once there was no river here, instead it was a mountain or large hill. Seismic activity occurred, causing cracks to form in the rock. The water got into the cracks and over a very long time of freezing, thus expanding, and thawing the crack got wider and wider until the river busted this mountain open. The line on this rock shows the same type of seismic activity that occurred all of those years ago. I’ll talk more about it in my GORP next Tuesday.
