Let's Talk Arches In Arches National Park
Happy and sad to say we've made it to the last National Park on our Utah Tour for this blog series: Arches National Park! This park is appropriately named because it has the densest concentration of natural stone arches in the world! It's most popular arch can be seen above and named "Delicate Arch."
There are over 2,000 documented arches in the park boundary! The arches range from thin cracks to spanning greater than 300 feet, like the landscape arch. The intriguing thing about this park and it's geological features are how they formed. First, the are held a specific kind of sandstone named "entrada," from the Jurassic period.
The entrada sandstone was in the area from a previously existing dessert that was full of shifting dunes and fine grained sand. The entrada sandstone hardened into a large sheet BUT was very porous and had many tiny little holes. After the hardening, came the parallel cracks. These cracks, in combination with just the right amount of rain created erosion! This erosion formed long, dome like hallways called "fins."
Since the creation of fins, erosion continued with as little as 8-10 inches of rainfall a year. This rain slowly dissolved the calcite bonding in the sand at just the right pace. This "rotted" the rock from the inside out. If this erosion had occurred any faster, we wouldn't have the arches that we do today. The same erosion caused many varieties in the shapes that began to appear as arches. To be an official stone arch, a hole must have an opening of at least three feet in any one direction.
In addition to arches, the park has many other geological formations such as: balanced rocks, petrified dunes, a rock garden called "fiery furnace," a standing rock called "dark angel," (pictured above) and many more.