Mt. Bross, Middle Park/Upper Colorado River

Immediately above the Hot Springs, Mount Bross rises abruptly for over 1,500 feet. It is composed throughout of the characteristic lignitic beds, mainly coarse grits and sandstones, yellow, gray, and white, with laminated arenaceous shales, which contain many fossil leaves, barely, if any, disturbed from a horizontal position.

Annual Report for the 1873 Field Season (Hayden 1874, 168)

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View East up Grand River from Mt. Bross, Middle Park

(Annual Report for 1873 Field Season [Hayden 1874], Figure 16, after page 170)

DRAWN/TAKEN FROM GEOGRAPHIC COORDINATES: LATITUDE: 40°05′01′′ N | LONGITUDE: 106°07′01′′ W | UTM zone 13N | 404,782 mE | 4,437,424 mN
VIEW ANGLE: West-northwest clockwise through north-northeast | COUNTY: Grand | NEAREST CITY: Hot Sulphur Springs

This view is from the far eastern crest of Mt. Bross (don’t confuse this Mt. Bross with the 14,172-foot Mt. Bross just south of Hoosier Pass in the Mosquito Range). You are looking upriver on the upper Colorado. The dipping sedimentary rock formations are typical of the Middle Park landscape.

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Middle Park is the smallest of the four major parks that run from the northern border of the state (North Park) to the southern border (San Luis Valley). These parks are specifically and geologically defined as large, relatively flat, structural basins surrounded by higher mountains. These basins are all at relatively high elevation themselves but are down dropped in relation to the surrounding terrain by faulting. When the mountains are uplifted, the parks are also, just not to the extent as the bordering mountains.

When one gets an expansive view of North and South Parks and the San Luis Valley, they look basin-like with almost homogeneously flat terrain and relatively uncomplicated topography. They are not homogeneous, of course, but in comparison to the much more geologically and topographically complex Middle Park, they certainly appear so. The William Henry Holmes landscape drawing for this section vividly shows the geologic complexity of Middle Park. Holmes is drawing from a vantage point at the far southern end of Mt. Bross, high above the small resort town of Hot Sulphur Springs. The town is named for the springs that emanate from deep fractures in the bedrock that allow sulfur-laced hot waters to work their way to the surface. You cannot see these springs in the drawing/photograph.

Holmes is looking generally eastward, and the complex geologic structure stands out even to the geologic neophyte. The first impression is of gently bent rock strata that are part of a large synclinal feature—a syncline being a concave upward fold of rock strata. Because of erosion, the southern (to the right) flank of the syncline has several levels of exposed strata. These folds were the result of some of the orogenic episodes that uplifted and compressed surrounding areas unevenly, and through time and pressure folded these rock layers.

Most synclines are composed of sedimentary rock strata. Here that is essentially true, but there exists another landscape element that adds some more complexity. There has been considerable volcanic activity throughout Middle Park, and this eastern end of the park has its share. Many of the exposed rocks in the syncline are volcanic (doleritic) breccia strata that are hard and resistant to erosion. These volcanics are a substantial part of the left-hand two-thirds of the scene.

The right-hand one-third of the scene shows less severely folded sedimentary layers that are part of a large collection of rock called the Middle Park formation. This is a Paleocene or lower Tertiary deposit of arkosic sandstone and conglomerate along with small coal or near-coal strata and having volcanic clasts embedded in the rock matrix. Hayden and his survey team write about rock such as the Middle Park formation as being “lignitic.” This is one of his most used descriptions pertaining to almost any rock that might have contained any amount of organic matter that may or may not have turned to coal.

There are some small ridges at the bottom left of the drawing that are called “Cretaceous quartzite” that are now referred to as the common Dakota sandstone. The Hayden Survey uses the term quartzite to mean sandstone made up mostly of quartz grains; modern use of the term quartzite usually refers to a metamorphosed sandstone. To add some more geologic confusion to the scene are some Precambrian gneissic-granites in the lower right-hand section. And finally are the innumerable faults, from very small to large, that cut across the terrain of the scene and Middle Park. The portion of the chapter in the Annual Report for the 1873 field season (Hayden 1874) that this panorama depicts was written by A. R. Marvine. He writes in excruciating detail through several dozen pages of the report about this small segment of Middle Park. Obviously, he too was quite taken by the convoluted nature of the geology here.

When one first reads the title of this drawing, “View East up Grand River from Mt. Bross, Middle Park,” the natural assumption is that the Grand River will be the main topic of the sketch. Marvine, however, hardly mentions the river, which even then was known to be the biggest river in the territory. Water is (and was) critical to Colorado (see section 1, on Colorado Springs/Pikes Peak). It is often cited that Colorado is the headwater area for several major rivers that have huge economic and social impact on the West—it is at times referred to as the “Mother of Rivers.” The four most significant include the rivers of the Grand (now called the Colorado), Rio Grande, Arkansas, and the Platte (both North and South). The Grand/Colorado has the biggest impact and affects the hydrologic life of seven states and Mexico.

MiddleParkMiddle Park, East from Mt. Gross
(photo by William Henry Jackson, courtesy of the University of Chicago Library) Jackson’s several photos of Middle Park provide more information about the “Grand” River than the text in any of the Survey’s reports (Hayden 1874).

During the late nineteenth and early twentieth centuries, immigration into and development of the West was at a fever pitch. Much of this development was in farms and ranches, but there was also mining and rapid urban growth too. All of these activities take water, and water is scarce here. California was in particular a huge development nexus, especially in the south around the Los Angeles Basin, during this time. It was obvious even to a casual observer that the Colorado River was the backbone of water for the entire region. Water wars, both in and out of court, were increasing exponentially.

Finally, Congress mandated that the water in the Colorado River be divided up equitably and legally; the negotiations that took place produced what is called the Colorado River Compact of 1922. This is when the name of the Grand River from its headwaters in Rocky Mountain National Park to its junction with the Gunnison River at Grand Junction, Colorado, was renamed the Colorado River. The upper basins states (Colorado, Wyoming, Utah, and New Mexico) would get an allocation of 7.5 million acre-feet of water per year, and the lower basin (California, Arizona, and Nevada) would get an equal amount to be divided up by each basin as they saw fit. Mexico would receive the remainder of the river water, about 1.5 million acre-feet per year, although this was not established until a treaty was signed with Mexico in 1944.

All seemed pleased with the compact except for the fact that the total assumed volume of water (16.5 million acre-feet) was determined during a very wet time period in the Southwest. Today the average flow of the Colorado River averages less than 15 million acre-feet and may be even closer to 13.5 million acre-feet. All of the problems, intrigue, and legal battles that this shortfall causes are beyond the scope of this project, but it does not take much imagination to get an idea of the renewed water wars (almost all in court this time) that this overallocation causes and will continue to cause long into the future.

One of the general characteristics of the landscape drawings in the Hayden Survey publications is the nearly total lack of vegetation depicted in the scenes. The most obvious reason for this is that the survey was looking mostly at the geology, topography, farming/ranching potential, and mineral resources. The natural vegetation was not a big part of their work, even though the extensive forests of Colorado were considered a valuable resource themselves. But if Holmes had drawn in the vegetation, at least at close range, you would have seen many landscapes covered in extensive forests. Large stands of spruce, fir, and aspen would be in evidence. Even larger, more expansive stands of lodgepole pine, with its olive green tint, would fill large parts of the panorama.

Lodgepole pine is a species of tree eminently adapted to its environment. The name is apt because the tree grows very straight and narrow with few branches, and Native American groups often used the trunks for the poles for lodges and teepees. The dominant ecological characteristic of the lodgepole pine is that it has adapted to and become dependent upon fire. In fact, the lodgepole pine forest is one of the best indicators of frequent fire zones in the mountains. For example, the tree’s cones are mostly serotinous, meaning that they actually need fire to open and have the seeds within dispersed. Beginning growth occurs rapidly after the fire has gone through an area, giving the lodgepole pine ecosystem the designation of a pioneering species. A major example of a lodgepole pine forest fire is the Yellowstone National Park conflagration in 1988; almost all the areas burned were lodgepole, and after twenty-plus years the forest is recovering well.

A common vegetation community characteristic of the lodgepole is how tightly spaced the trees grow. A stand is often called a dog-hair forest because the trees are as close together as the hair on a dog’s back. This dense forest and the fact that fire has been suppressed in almost all forestlands in Colorado over the last century leads to a serious problem now faced by people in Middle Park. A natural pest that periodically appears in pine forests of the West is the mountain pine beetle (Dendroctonus ponderosae). The beetle itself weakens the tree as it lays its larvae in the outer, cambium or phloem layer of the tree. This is the section of the trunk that acts as a conduit for nutrients and water. Beetle-affected trees will have innumerable tunnels and galleries etched out by the parent beetle where the larvae can incubate.

The real killer for the tree, however, is a fungus that the beetle carries that spreads and clogs up the sapwood. The wood is stained blue by this pathogen, hence the name, blue-stain fungus. Trees killed by the beetle/fungus team will have a very distinctive blue color in the wood. Once the tree is infected, there is almost no hope of saving it although the pines have developed a few mechanisms for getting rid of the beetles before fungal infection.

Usually only localized infestations occur, and the beetle threat recedes. Because the beetle cannot fly, it must be in close proximity to other trees for it to spread. This is exactly the scenario in Middle Park in which the lack of fire has allowed dense stands of trees to develop. Huge, homogeneous areas of pines (mostly lodgepole but some Ponderosa) have been devastated since the mid-1990s and the epidemic is spreading. Control (almost never total eradication) of the beetle can occur in several ways. Fire can obviously clear out the dense forest and give the beetles nowhere to spread. Extreme cold weather, –30 degrees F or lower, for at least five consecutive days will kill the larvae. Spraying with pesticides has resulted in limited success. Finally, drastic thinning of the tree stands will make it more difficult for the beetles to spread. Currently, Middle Park is the center of the beetle problem in Colorado, but other areas are bracing for a similar fate (see section 7, on Longs Peak).

The beetle kill in this area may become an ironic reflection of the past. With the loss of all of the trees, the landscapes of Middle Park might end up looking eerily similar to the nearly treeless drawings seen in the survey depictions. The cycles of nature move slowly but always inextricably as we may see in the near future here.