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Numerous shield volcanoes created the surrounding lava rich landscape, and now the rest of the story...
Somewhere around 15,000 years ago, Lake Bonneville, currently known as The Great Salt Lake, broke free and created this awesome canyon. Known as the Bonneville flood, it changed the Southern Idaho landscape forever.
It should be noted that the Perrine bridge is the only bridge in the United States that allows BASE (Building, Antennae, Span, Earth) jumping 24 hours a day, seven days a week, without any special permits or permission. I saw some kids jump off at midnight on a full moon and they screamed like girls, oh wait, they WERE girls! HA!! At roughly 490 feet from the deck of the bridge to the water it is a popular destination for BASE jumpers from around the world.
Picture it: 15,000 years ago, The ice is melting, glaciers are retreating and some of the water has no where to go. Lake Bonneville became that place but with no natural outlet, the water became deeper and deeper until it reached a size of 19,691 square miles, 984 feet above the current level of modern day Salt Lake. The massive body of water refused to stay within its natural boundaries and broke free at Red Rock Pass. The flow has been estimated at 9.5 cubic miles per hour! At that time, the river bed was in place but it didn’t look anything like this! The rushing water had so much power that it was able to roll rocks the size of small houses; round, sort and deposit large fields of smaller rocks known as melon gravel (visit Hagerman Valley); and scour the surrounding land of it’s topsoil. Notice that there isn’t much farmland near the rim of the canyon. The force was so incredible that this canyon was cut in a short two months. The flood continued for about a year, but most of our damage was already done.
Idaho has more volcanoes than any other state in our great nation. It’s just that most of ours are extinct or dormant. This explains the large amount of lava in the area. Looking across at the opposite canyon wall, one may notice the many layers of basalt, each topped by a thin layer of soil and representing an individual lava flow. The hotspot that caused much of the volcanic activity is the same one that is currently under Yellowstone at this time. Basalt and rhyolite are two types of lava that come from volcanoes. Rhyolite is more gaseous and explosive and cools to be much harder than the basaltic lava you generally see in our desert. This rhyolite is what allowed the Shoshone Falls and the Twin Falls to be formed. When the rushing flood waters ran out of basalt to gouge away, what was left was the harder rhyolite that still stands.
FYI:The height of Shoshone falls, also known as The Niagra of the West, is about 200 feet! Visit during the spring for the best waterfall views. Be sure to grab the other caches in the area.
Nearby is a statue of Ira Burton Perrine, the man who figured out how to get that water down there, to good farmland up here. In order to log the cache, look across the canyon at the layers of lava. email the number of layers you see in the north wall and the name of the artist who sculpted Ira.
Now think about this: How much force does it take to move a rock the size of a small house??!! These are the things that amaze me.
Ybbx ba gur onfr.