About a millennium and a half ago, well before Europeans explored North America, a group of people in the Four Corners region chose Mesa Verde for their home. Within Mesa Verde are north-south running canyons, with cliff walls rising an average of 650 feet above the canyon floors. The mesa tops, canyons, and cliff alcoves of Mesa Verde supported families of Ancestral Puebloans (also known as Anasazi) for over 700 years. What drew them to this area? Is there something special about Mesa Verde that may have allowed them to live in one place for so long? This Earthcache is intended to lead you in the discovery of geological clues and to consider how the geology of Mesa Verde helped support the people that lived there for so long. It specifically focuses attention on one of the cliff dwellings in Mesa Verde National Park, Balcony House.
Much about the people who created and lived in Balcony House is still unknown. At Mesa Verde, geology and archaeology come together to create a sense a wonder - it is the specific geology of this area that helped support the people who made their home here. Balcony House and the other cliff dwellings in Mesa Verde National Park are located amid such a geological marvel, they have also inspired archaeologists to study these ancient structures. Despite efforts in excavation and study, the lack of any written records leave much to be unknown. However what is known is that the Ancestral Puebloans were expert builders, craftspeople, and skillful in making a living in a difficult environment.
The first Spanish explorers to the area called it Mesa Verde, or “green table.” This expression is actually a misnomer. The correct geological term for the area is a cuesta, not a mesa. Mesas are isolated, flat-topped highlands with steeply sloping sides or cliffs, and are topped by a cap of much harder rocks that are resistant to erosion. The cap protects the softer underlying slopes or cliffs from being quickly weathered away. The only difference between a cuesta and a mesa is that a cuesta gently dips in one direction. Mesa Verde is inclined slightly to the south at about a 7-degree angle. This cuesta is made up of many separate, smaller “mesas” situated between the canyons.
The southern dip of the cuesta helps to produce a longer growing season and higher precipitation on the mesa top than down in the valley below. It is also this 7-degree dip of Mesa Verde that contributes to the formation of the alcoves in which most of the cliff dwellings are found. The alcoves provided the spectacular preservation of this architecture. Alcoves are large, arched recesses formed in a cliff wall. Alcoves differ from caves in that caves are underground chambers, not found in Mesa Verde. Alcove formation is caused by water that seeps into cracks, travelling down through a porous sandstone layer, freezing and thawing in them, eventually expanding and slowly pushing the rock apart. These portions fall off in blocks, creating the alcoves seen at Mesa Verde. These blocks of sandstone were shaped and used by the Ancestral Puebloans in the construction of their homes. Areas of shale (that water cannot penetrate) below the sandstone layers force the once downward flow of water to move sideways within the rock. This creates seep springs, pockets of water emerging from cliff faces.
Mesa Verde is quite interesting for the combination of geology and erosive forces that shape the canyons of the area, and it is this fascinating geology that enabled the Ancestral Puebloans to inhabit the cliffs that these canyons created. Their lives were undeniably intertwined with the earth and all of nature surrounding them. If not for the amazing combination of geological processes at work here, the people may not have made Mesa Verde their home.
|Qualifying to log a find: take the tour, and then... Email the answers to the questions; do NOT post the answers or spoilers in your log. Logs that give away the answers or are unaccompanied by an email with the answers will be deleted.
- Estimate the width (in feet) of the dwelling of Balcony House.
- What type of sandstone is prominent here?
- How did the sandstone (as opposed to some other kind of rock) contribute to the survival of the cliff dwellers that lived here? Describe something you see in Balcony House that is evidence of how this kind of rock could contribute to their survival.
- (Suggested, not required) While IN the Balcony House (NOT at the trailhead above) take a photo of you and your GPSr, showing something in the background that makes it clear you're in the Balcony House (for example, see this photo).
- Optional, use your GPSr to take one elevation reading at the trailhead and another elevation reading from inside Balcony House. Report both readings and the difference in feet of elevation between the two. At the least, estimate the difference between the elevation at the trailhead and inside Balcony House.
Your answers should be emailed when you post your find.
Note: Since Balcony House is a part of Mesa Verde National Park, there is an admission fee to enter the park. Also, Balcony House, which isn't visible from any road, is accessible only by a ticketed, ranger-led tour; tickets can be purchased at the Visitor Center for $3. Please note the terrain rating. While it is a short hike to Balcony House, it is steep and possibly challenging for those with a fear of heights or with claustrophobia; the hike includes a climb up a 32-foot ladder and a short crawl through a tunnel. The coordinates posted for this cache are for the trailhead at the start of the ranger-led tour, but you need to purchase your ticket first at the Visitor Center. The tour is available during late-Spring to early-Fall; call for precise dates. It will certainly be a highlight of your visit to Mesa Verde!
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