Blanco Canyon Earthcache EarthCache
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This earthcache will teach you about how Blanco Canyon and the surrounding landscape, the Llano Estacado, formed. There is no physical cache container to find; to log this earthcache, you will need to email or message us the answers to the questions below. The questions are repeated in the unencrypted hint for your convenience.
The logging questions can be answered from the posted coordinates in the picnic area. There is a trail over the fence open to the public if you want to inspect the caprock layer or the Quanah Parker Trail arrow up close -- please feel free, but it's not required to log the cache.
THE LLANO ESTACADO
Blanco Canyon is located on the eastern edge of the Llano Estacado, a high, gently sloping mesa that stretches over much of northwest Texas and eastern New Mexico. These plains were once the domain of the Comanche tribes, and this canyon was the site of a fierce 1871 battle between Comanches led by Chief Quanah Parker and US Army troops led by Colonel Ranald Mackenzie, one of the last major skirmishes in the Indian Wars. Even now, this area is still a stark, sparsely populated region. The name Llano Estacado, which literally translates as the Staked (or, more properly, Palisaded) Plains, comes from the appearance of the escarpments at the edge of the plateau. The White River has eroded Blanco Canyon into the eastern edge of the Llano Estacado. As one of the historical markers will tell you, archaeologists confirmed that Spanish explorer Franciso Coronado's expedition twice camped around this area in 1541.
The Llano Estacado gets its name, "palisaded plains," from the appearance of the escarpments on its edge; the sediments under the caprock slope dramatically down from the edge of the plateau, forming sheer cliffs in some areas and steep slopes below the caprock in others. To the east, the Caprock Escarpment forms the border between the Llano and the red Permian plains of Texas; to the west, the Mescalero Escarpment demarcates the edge of the Pecos River valley. The Llano has no defined southern border, it blends into the Edwards Plateau around Big Spring, Texas. Blanco Canyon is sort of a "tributary" of the Caprock Escarpment. The White River formed the canyon as it cut into the caprock and down into the softer underlying sediment.
THE OGALLALA FORMATION
Based on current scientific theory, when the Rocky Mountains lifted up during the Miocene Period, around 65 million years ago, they pushed aside a massive amount of sediments, similar to a very large, very slow mudslide. This alluvial fan spread over an area the size of the state of Indiana: about 150 miles from east to west and 250 miles from north to south. The sand, silt, clay and gravel cemented and hardened into a rock-like layer of calcium carbonate called caliche. This caliche layer is called the Ogallala Formation, and it is present not only here on the Llano Estacado, but elsewhere in the High Plains east of the Rocky Mountains. Also called caprock, this hard caliche layer defines the Llano Estacado. Although the Llano seems to be relatively flat, it is in fact a very gentle slope, about 10 feet per mile, with elevations ranging from 5,000 feet in the northwestern portions (where the alluvial fan started) down to 3,000 feet at the far end to the southeast.
Both the Llano and the surrounding lands are part of the Permian Basin, so named because the area contains one of the thickest layers of sedimentary rock from the Permian Period (about 250 to 300 million years old). But while the lower lands of the Permian Basin below the Llano Estacado have somewhat rolling hills, the weather-resistant caliche layer has maintained the Llano's gentle slope. Where the caprock has weathered away, like it has here, it tends to form dramatic landscape like arroyos and canyons -- once the harder caliche wears away, the layers underneath tend to weather away much more easily.
FORMING THE CAPROCK
The layer of caliche is basically naturally formed cement -- in fact, when it is mined away, it can be used to manufacture cement. The mineral that makes up the sediments of the Ogallala Formation, calcium carbonate, dissolved in water. Over time, as the surface of the ground dried, the mineral laden water was pulled to the surface by capillary action. The calcium carbonate precipitated and cemented together the sedimentary layer at the surface, forming caliche. The thickness of the caliche varies throughout the High Plains, in some places even reaching 400 feet thick.
THE TREELESS PLAIN
When Spanish explorer Francisco Coronado first explored this area, he was taken aback by the lack of vegetation. "I reached some plains so vast, that I did not find their limit anywhere I went, although I traveled over them for more than 300 leagues ... with no more land marks than if we had been swallowed up by the sea ... there was not a stone, nor bit of rising ground, nor a tree, nor a shrub, nor anything to go by." This lack of vegetation comes from a lack of groundwater. First, the area is relatively arid, averaging only about 20 inches of precipitation a year. And even when it does rain, the ground does not retain the water. The caliche layer in the Llano is close to the surface. Water cannot penetrate the caliche layer easily, and the soil on top of the caprock is too thin to retain water when it rains. Because of the overall slope of the Llano, water runs off from west to east. Over time, this surface runoff carved canyons, like Blanco Canyon here.
LOGGING THIS EARTHCACHE
To log this earthcache, email us or send us a message (visit link) and copy and paste these questions, along with your answers. Please do not post the answers in your log, even if encrypted. There's no need to wait for confirmation from us before you log, but we will email you back if you include your email address in the message. Group answers are fine; just let us know who was with you.
1. The name of this earthcache: Blanco Canyon Earthcache
2. The coordinates take you to a stone marker surrounded by a border of smaller rocks. Describe the appearance, texture, and colors of the stone marker and the border rocks. How are they different?
3. Based on your observations of the caprock, do you think the stone marker at the coordinates is made from local stone?
4. Describe the layer of caprock on the rim of the canyon. What signs of weathering can you see?
SOURCES
J.B. Calvert, "Llano Estacado." University of Denver, (visit link)
Barry Hibbs, "Geophysical and Hydrochemical Analysis of the White River Alluvian Acquifer, Crosby County, Texas," California State University - Los Angeles, (visit link)
Texas State Historical Association: Caprock, (visit link)
Texas State Historical Association: Llano Estacado, (visit link)
Environmental Protection Agency, Ecoregions of Texas," (visit link)
Wikipedia: "Llano Estacado;" "Caprock;" "Blanco Canyon;" "Caliche;" "Rocky Mountains"
Additional Hints
(Decrypt)
[To log this earthcache, use the "send message" link in our profile and copy and paste these questions, along with your answers. Please do not post the answers in your log, even if encrypted. There's no need to wait for confirmation from us before you log, but we will email you back if you include your email address in the message. Group answers are fine; just let us know who was with you.
1. The name of this earthcache: Blanco Canyon Earthcache
2. The coordinates take you to a stone marker surrounded by a border of smaller rocks. Describe the appearance, texture, and colors of the stone marker and the border rocks. How are they different?
3. Based on your observations of the caprock, do you think the stone marker at the coordinates is made from local stone?
4. Describe the layer of caprock on the rim of the canyon. What signs of weathering can you see?]
Treasures
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