Mind-blowing!
Puts things in perspective like nothing else can!
Hiking in the Verde Valley and Sedona, I wondered about the layers of rock I see around me and walk over. Doing some research, I found this wonderful explanatory video of the geology of the area.
When the narrator went into the explanation of Geologic Time, my eyes were opened.
The Earth has seen 10 mass extinction events, 5 of which were great extinctions of life forms, 5 great ages. Each age is demarcated by the loss of at least 50% of its life forms. One extinction saw 95% loss of life forms.
The forces that cause this kind of extinction of life are hard to imagine.
Sedimentary rocks are dated by looking for certain life forms that exist only in that age. These life forms preserved in rock are called index fossils. When fossils present in a layer are absent in the next layer, we can date the changing of an age.
I wonder if our human remains will be an index fossil in the future, way far in the future.
For a long time Sedona was on the coast of a sea and many layers were deposited and formed rock. In addition, when the movement of tectonic plates caused the uprising of parts of these layers, distortions formed and eventually cracked, forming faults.
Later, volcanic lava erupted through these faults and other places, placing a layer of basalt over the sedimentary rocks. This picture shows the area around Sedona where the basalt rock remains after erosion.
There was lots of erosion over the eons, creating the layers of rock formations that we see.
The story of the Verde Lake and freshwater Verde Limestone is intriguing. The limestone seen in the Verde River canyon was from this lake, and is different from the limestone around Sedona.
Finally, the formation of sinkholes is evidence of even more erosion. There are seven evident in our area.
Check out the whole video! You may recognize areas in the photos and begin to understand their formation in the whole extent of geologic history.
I know the next time I am hiking, I will bring my notes and look for these layers and the differences in elevation due to faults and parts of the earth’s crust dropping. I am hiking over quite a complex history!
Please leave a comment below as to what formations you recognize on your hikes!
