Cochise College Student Papers in Geology
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Roger Weller, geology instructor regional geology planetary gems
wellerr@cochise.edu
Mesa Verde
Chelsea Hover
Physical Geology 101
Spring 2008
The Homes of the Ancient Ones
http://www.wd.gatewayreservations.com/Images/activities/mesa_verde_1.jpg
The builders of the great cliff dwellings in Mesa Verde and
the four corners region of the United States were a race of Native Americans
called the Anasazi Indians. They lived roughly from 200 to 1300 AD. The culture
lived in valleys and canyons creating large structures in the mountain faces of
the Four Corners region made up of sandstone and adobe. The culture declined
around 1300 AD and by 1600 AD all the villages were all abandoned, with no
explanation as to why.
http://www.eg.bucknell.edu/~hyde/dan/Southwest/Jpegs/SouthwestScanned/MesaVerde1.jpg
The park of Mesa Verde is located in Colorado which is part
of the Four Corner region. It was established by Congress on June 29, 1906 to
help protect the dwellings that the Anasazi Indians left behind. There are over
a thousand dwellings in the park, with only a few of them open to the public.
http://archtypevolution.net/wp-content/uploads/2007/04/lincoln-and-mesa-verde-114.jpg
“The sequence of rocks exposed on the mesas originated in a great inland sea that began to cover this area about 100 million years ago. As the water encroached over a low, relatively flat erosion surface, streams from the west brought sands and muds into the shallow water. These shoreline deposits consisted of beach sands, shallow water cross-bedded shore sands, lagoonal and swamp muds, and deltaic sands at the mouths of inflowing streams. These deposits are now the brown Dakota Sandstone seen in the Cortez Valley below the Mesa Verde. This particular layer is not exposed within the boundaries of Mesa Verde National Park.
The sea continued to advance until the Mesa Verde region was far out from the shoreline that was probably close to what is now the western edge of Utah, some 200 miles away. The sediments deposited change from the coarser, near shore, sandy deposits to fine, evenly bedded shales. In all, about 2,000 feet of Mancos Formations were deposited in quiet offshore conditions, and is now exposed in the steep, dark gray shale slopes of the north escarpment. Although the Mancos Shale appears to be a great shale mass, it is not one homogeneous unit. The sediments were deposited over a ten million year period and consist primarily of shales with some limestones. It took over 10 million years to deposit the 2,000 feet that make up the Mancos Formation. Variations in environments throughout time are well documented in rock types and in an abundant and varied fossil record. The sea reached its greatest extent during the deposition of the Mancos Shale, and then began a slow withdrawal. The Mancos Shale is visible as visitors drive into the park from the entrance station to approximately Mile Post 4 near the Morefield Campground.
Overlying the thick Mancos Formation is the Mesa Verde Group of formations. This group is subdivided into three formations; from the oldest, the Point Lookout Sandstone, to the Menefee Formation, to the Cliff House Sandstone, which is the youngest. The Point Lookout Sandstone is seen as visitors travel from Morefield Campground through the tunnel on the main road and then through Prater Canyon. As one travels through the switchbacks past the Montezuma Valley Overlook, exposures of the Menefee Formation become evident. Finally, upon reaching the Far View Visitor Center, the Cliff House Sandstone is the predominant formation visible.
Sand was brought into the sea, the water became shallower, and the shales became progressively sandier. The massive shallow water Point Lookout Sandstone overlying and grading into the Mancos Formation was named for the prominent Point Lookout overlooking the flat plain. Few fossils remain in this formation because sediments were deposited in a zone of vigorous wave and current action.
The sea continued to withdraw to the northeast, and a broad, low coastal plain emerged. Woody shales, coals, and coarse irregular sands were deposited in broad, shallow swamps and along stream and interstream areas and became the sediments of the Menefee Formation. Many plant fossils are evidence of lush vegetation and show that the climate was wet and warm during this period when the land was only slightly above the sea.
The sea again lapped farther south. Beach sands and shallow water sands were then deposited, forming the Cliff House Formation which now caps the mesa. This formation takes its name from the presence of the famous cliff dwelings in the alcoves and niches weathered in these sandstones. The alcoves are formed by the action of the ground water percolating through the porous sandstones until it reaches an impervious layer and then moves along this water barrier to the canyon edge. Freezing, thawing, chemical, mechanical, and wind eriosion all continue to enlarge the niches along the canyon walls. The Cliff House Formation contains many invertebrate and vertebrate fossils. Most of the vertebrate remains were broken due to wave action at the time of deposition. The fossils near the top of the formation have been dated at approximately 87.5 million years old.
http://www.carto.net/andre.mw/photos/1996/07/02_usa/1996071317_co_cliff_palace_mesa_verde.jpg
The largest dwelling of Mesa Verde is called Cliff Palace, discovered on December 18, 1888 by two cowboys. This dwelling has 150 rooms and 23 kivas, an underground or partly underground chamber in a Pueblo village, used by the men especially for ceremonies or councils, and had a population of about 100 people. It was not until 1909 that the sight was added to the park protecting it from the elements so it could be preserved. “Since sandstone is a very porous material, moisture seeps right down through it. Beneath the layer of sandstone, however, is a layer of shale through which the moisture cannot penetrate. In the winter months, when the moisture freezes and expands, chunks of sandstone are cracked and loosened.” Mesa Verde National Park.
http://cache.virtualtourist.com/3664186-Spruce_Tree_House_Mesa_Verde-Mesa_Verde_National_Park.jpg
Spruce Tree House is the third largest cliff dwelling in the park with 130 rooms and 8 kivas measuring at 216 feet at the greatest width and 89 feet at greatest depth. It was able to house roughly 80 people. The reason it was named Spruce Tree House was because of a large Douglas Spruce that grew in front of the dwelling. It was believed that the people that discovered the dwelling climbed down the tree to get to the dwelling originally. It was discover in 1888 by twp ranchers that lived in the area while they were looking for stray cattle. And due to the overhang in the cliff Spruces Tree House has needed very little supportive maintenance unlike Cliff Palace.
http://www.ancestral.com/images/cultures/north_america/anasazi/mesa_verde.jpg
Though these two dwellings are only two of over 600 in the park not all are open to the public. A few such as Cliff Palace you have to pay for a tour to explore some its rooms. While ones such as Spruce Tree House is always open to the public when the park is open since they have made paths so that people can get down to the ruins. But on the land near the park owned by the Native Americans there are a few dwellings that are inaccessible unless you clime down straight cliff to get too that are two to three time larger then Cliff Palace. And it is even said that when you are in a few of the dwellings that you feel that you are not alone when you are there.
http://www.nlcs.k12.in.us/oljrhi/brown/bricks/MesaVerde.jpg
References
http://www.essortment.com/all/nativeamerican_refe.htm
http://www.mesa.verde.national-park.com/info.htm
http://www.nps.gov/archive/meve/home.htm
