Use of geocaching.com services is subject to the terms and conditions in our disclaimer
On the Colorado side of the Wyoming/Colorado border, lies a Natural Fort- created by volcanic ash that drifted from explosive volcanoes in Nevada. This area has a rich social history as well.
This sandstone formation called, Natural Fort, was created by poorly consolidated Tertiary sedimentary rocks. The formation occurs on both sides of I-25, but the Eastern side is the larger of the two.
The Tertiary Period lasted from 65 million to 1.8 million years ago. Invertebrates, fish and reptiles were similar to those of modern types, but mammals, birds, and flowering plants would undergo considerable evolutionary change.
The Oligocene Epoch extends from about 34 million to 23 million years ago. The Oligocene is often considered as an important window of environmental transition from the tropical Eocene and the cooler Miocene. The start of the Oligocene is marked by a major extinction event that might have been caused by a meteor impact in Siberia or near the Chesapeake Bay . Temperate deciduous woodlands mostly replaced tropical and sub-tropical forests, while plains and deserts became more commonplace. Among the animals, mammals diversified markedly, and marine fauna evolved to forms closely resembling those extant today. Ancestors of modern elephants and rhinoceros grew to large size in Africa , where the first apes primate belonging to suborder Anthropoidea that includes monkeys, apes, and humans, also appeared. (fossilmuseum.net)
East of here in this same rock, the Oligocene White River Formation, in the Badlands of Colorado, South Dakota and Nebraska, “many fossil vertebrate skeletons have been discovered in these sediments: saber-toothed tigers, rhinoceroses, camels, little three-toed horses, giant pigs, turtles and strange rhinoceros-like titanotheres.” (Chronic and Williams, 60).
Badlands are formed by the cutting action of rivers and streams flowing over a steeply sloping face of soft, fine-grained material composed mainly of clay and silt. The intricate carving by thousands of small streams of water produces the distinctive rounded and gullied terrain, called badlands.
Within the Natural Fort Badlands, “there are numerous tight and easily defendable passageways leading to the interior of the fort. Several internal open areas are well protected by the nearly continuous walls, which never dip below 10 feet in height.” (Gregory, 70)
Jim Beckwourth was an African American who played a major role in the early exploration and settlement of the American West. Beckwourth lived among and acted as a chief of the Absaroke Crow Indians. Although there were people of many races and nationalities on the frontier, Beckwourth was the only African American who recorded his life story, and his adventures took him from the everglades of Florida to the Pacific Ocean and from southern Canada to northern Mexico . (Beckwourth.org)
In Beckwourth’s autobiography, he describes a battle that took place at the Natural Fort:
On November 21, 1834, the Crow came across a large party of their enemy the Blackfeet. The Blackfeet took refuge in the Natural Fort, and then many more Crow came to the scene to make a sort of siege. According to Beckwourth, the Crow chiefs decided that the Blackfeet were not assailable from their strong position in the fort, and decided not to attack, but Beckwourth convinced them to try. The Crow made a large diversion on one side of the fort and then stormed in from the other. The sheer numbers involved according to Beckwourth would mean that bodies would be packed in close together in the battle that followed. He describes such a scene of carnage and blood. About forty Crow warriors were killed, but the Blackfeet were completely annihilated.
On the rock formation, you can view various iron concretions which have weathered out of the sandstone. A concretion is a volume of sedimentary rock in which mineral cement fills the spaces between the sediment grains. Concretions are often spherical in shape, although irregular shapes also occur. Concretions form within layers of sedimentary strata that have already been deposited. This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum.
Concretions have long been regarded as geological curiosities. Because of the variety of unusual shapes, sizes and compositions, concretions have been interpreted to be dinosaur eggs, animal and plant fossils (called pseudofossils), extraterrestrial debris or human artifacts. (Wikipedia.com)
See if you can find some and post your pictures!!
In the 20 miles south of here, other interesting geological features appear.
From milepost 293 to 281, I-25 crosses over the late Cretaceous Sandstone, you may be able to notice the soil next to the highway; this sand was once the beach of the Creataceous Sea . Is this soil rich or poor? Notice the agricultural useage of this land, is it rangeland or farmland?
Immediately upon crossing from the Cretaceous Sandstone at mile post 281, the land now is on top of the Pierre shale. Even with the encroaching city, is the soil too fertile for townhomes? Is this area rangeland or farmland?
To log this Earthcache:
Email the answers to the Cache Owner when you log your find.
1. Where is it better to be a farmer, on the Sandstone or Shale?
2. At the Natural Fort, is the sandstone hard or soft?
3. and if you care to, please Post a picture of your favorite view of the fort.
Colorado Scenic Guide: Northern Region
By Lee Gregory
Edition: 3, illustrated
Published by Big Earth Publishing, 1996
Roadside Geology of Colorado by Halka Chronic
Mountain Press Publishing Company (June 1980)
T. D. Bonner, The Life and Adventures of James P. Beckwourth, University of Nebraska Press Edition, 1972.
and of course...
Nccebnpuvat sebz gur Fbhgu, lbh jvyy arrq gb ragre Jlbzvat, Rkvg 2 naq qevir 3 zvyrf fbhgu ba Greel Enapu Ebnq