Rock Surficial Chemical Weathering Processes Igneous andesite in the NW Oregon region is composed of a gray colored porphyritic structured matrix (phenocrysts of larger crystals in a fine groundmass). plagioclase and other minerals, enveloped in a fine grained crystalline or glassy groundmass. The large crystals are composed of plagioclase (pyroxenes, irons etc) in a silicious groundmass, giving a resultant andesite total hardness scale of 6 (Mohs' scale 1-10). Hmmm....let's analyse this further.
Decompositional erosional weathering factors typically include chemical, pressure, and high temperatures, individually, or in various combinations usually sourced from water, ice, sun, or wind. Additional factors include other external erosion events (i.e. mosses & lichens), and while some events may be short, most are longer term activities, thus the entire process tends to be somewhat more visible over a series of many years. Metamorphosis involves deformation of the rock structure, but may include breakage, and smearing factors expressing a degree of torque upon the mineral grains and its matrix.
The mineral crystals found in the gray groundmass of andesite are a strong, well-embedded, erosion-resistant part of the rock matrix structure. The various inclusive andesite rock minerals may range from quartz, feldspars, hornblende, olivines, pyroxenes, biotite, etc. Most of these minerals are not soft; many fall in the the upper end of the 1-7 hardness spectrum. For example: Quartz (7), Olivine (6-7), Feldspars (6-6.5), Hornblende (6), The mineral stabilty of andesite is at the high end of the erosional scale.
When other additional chemical weathering decomposional events intermix, it produces varying degrees of total erosion, by precipitating or dissolving once solid rock down into constituant base elements, which include silicates, aluminum, iron, calcium, and magnesium, which become part of the gravels, sands and mud of all valleys.
For emphatic comparison with other metamorphic or sedimentary rock (using the Mohs' scale hardness factor) the differences in structural rock strengths are quite notable:
Dolomite rock: H 3-4; Limestone rock: H 3-4; Shale rock: easily scratched with knife; Slate rock: scratched with knife; Gneiss rock: H 6-7 unless full of mica. For Sandstone rock the hardness factor varies broadly based upon the cementing materials, which range from silica, carbonates, clay to iron oxides. If the cementing compound and grains are quartz a harder sandstone results. The "gritty" feel of sandstone is based on the grain size, and also when the structure breaks around those grains through the cementing material.
Mosses and lichens (see below) and its underlaying base detritus have a substantial impact on the surficial nature of the boulders, in that they retain both chemical elements (moisture), while actively growing within crevices or weaknesses of the rock matrix, often enhancing the very pockets and tiny crevices which you relish to use for crimps or to hold your foot smear. The source of the gaseous pockets (large and tiny) are incorporated into the original magmas, but are most definitely enhanced (smoothed or etched) by all the later weathering processes. It can be worn smoother or more deeply etched depending on the stability of the groundmass and the various weathering factors. In certain cases a fresh cleavage of stone will yield a smoother surface lacking the grainy texture so desireable for quality crimps and smears for bouldering. On a historically recent lava flow fields, where the chemical weathering and flora aging factors are still minimal (such as the lava field one mile west of Parkdale) jagged rock is prevelant.
Part of the reason why basaltic-andesitic rocks are quite common in the NW Oregon region is because of their long term stability, or resistance to simple or rapid erosional processes. Sandstone (such as found at the Oregon Coast) simply erodes rapidly because of the Pacific Ocean salts and water (chemical) reactions break the rock structure down quickly. Another important weathering factor at Lost Lake Boulders is the 6-month stretch of snow that envelopes all the boulders, as it provides a remarkable encapsulated chemical weathering process on a yearly basis, which essentially ever so slightly alters or removes some minute rock fragments. The freeze-thaw winter cycle, and the hot-cold summer cycle, yields processes that are prime factors effecting the mineral "crispness" of the boulders crimp holds. The freeze-thaw cycle has an expansion ratio of approximately 3%, an impressively effective means of minute surficial erosion of the boulders.
Waters percolate thru/into rock, precipitating, but also can enhance the growth of quartz crystals. Water dissolves and transports soluble materials, taking the chemically weaker materials first, enhancing the surface prominence of quartz-feldspar products (one of the other benefits of rainfall).
Mosses (Peat and True), Clubmosses, and Liverworts:
Some additional important factors in rock surficial etching. Mosses develop into two growth components, gametophyte (the leaf and root-like filaments called rhizoids) and sporophyte (the stalk and a capsule at the tip). Though lacking true roots, the rhizoid does seek minute features or pockets which to nest in for germination purposes. True mosses, over 600+ species strong, grow at all elevations (sea level to alpine) and have the ability to live in either moisture heavy, or moisture limited spots. Brophytes have the ability to live in dry places. During long dry seasons it may appear dead and dry, but quickly relivens when rain or moisture returns. Many True Mosses prefer dry acidic inorganic rocky mineral-rich, sandy or gravelly detritus surfaces or soils, such as the varieties of mosses found at Lost Boulders. Other mosses do superbly well in wet organic humus detritus based zones of shaded forested environments under fir and hemlock trees. Acidic, calcium rich rock faces or soil zones at Lost Boulders provide a suitable environment for luxuriant moss growth activity. Some varieties such as Amphidium lapponicum (Bottle Moss) thrive on moist silicious (silica-rich) basaltic-andesitic rock surfaces, while the Schistiduim apocarpum (Beard Moss) enjoys calcium-rich dry rocky surfaces.
Lichens:
Lichens are a fungus, cultivating photosynthesized algae within, providing the algae with carbohydrates, vitamins, and proteins. Lichens also thrive in variable locales, from open-sloped boulder or talus slopes with an acidic environment, while others grow in ventilated somewhat shaded tree zones. They generally prefer acidic mineral soils, and tend to concentrate radiation atoms to a considerable higher degree than other plants.
Basaltic-andesitic rock has a variety of minerals, from iron, magnesium, potassium, to aluminum silicates. Two common features to look for are Quartz and Feldspar (which has a mixture of either a sodium-rich oligoclase predominance, or blends across to calcium-aluminum rich silicates at the other end of the spectrum. So, its certainly understandable why mosses and lichens flourish on talus and boulder fields in that they are seeking these very constituent elements which boulderers so rapidly attempt to scrub away. But, like the seasonal rainstorms, most mosses and lichens rapidly re-germinate.
Calcite (calcium carbonate) chalk, which has a hardness factor of 3, when utilized in conjuction with grinding pressure (both hand and foot) may have some reductionary effect on the original crispness of the crystalline minerals. Though one might consider limiting the use of chalk, on the other end of the point, calcium is a desired mineral for lichens/mosses and tends to assure a rapid regrowth session.
To use or not to use a brush. A few swipes with any type of brush removing the initial moss/lichen is unlikely to have any substantive impact other than the loss of the moss/lichen element for one season. Moss/lichen growth tends to enhance surficial features. The long-term boulderer generally effects the long-term quality of the bouldering lines crimp holds by repeated use. The slower processionary factors found in a long-term chemical weathering process, may increase a bit by the human event factor, and may eventually reduce some of the "crispness" features of the original angular cleavages of the surface crystalline mineral grain crispness via foot pressure.
To boulder or not to boulder. The logical solution perhaps, is to simply diversify, and send a variety of lines. Frequent different areas, run a variety of lines in a day, explore and tap and expand other bouldering sites scattered over entire broad regions, so there will be a tremendous selection available, thus minimalizing the compounding effect of reductionary abration of the surficial mineral grains of the andesite. If subjectivity is an issue, avoiding the bouldering or climbing game simply assures a much longer gradual erosional period being placed on the boulders. When objectivity is the desired goal, plethoric diversification is your brothers best friend. On the plus side, many types of mosses and lichens have rapid regrowth, and will continue to do its specifically designed processes, enhancing surface mineral characteristics through the etching pronouncement processes that remove the softer base matrix.
Naturally, rock surficial resistance is generally quite high for basalts and andesites, the two most common rock types found within this region that are frequently rock climbed upon.
Rock shoe rubber, using the Shore A Hardness (Durometer) Scale is approximate with the Durometer A range of auto tire treads, a method that tests its elasticity hardness on items ranging from plastics to rubbers. The Mohs hardness scale compares scratch resistance against another substance.
For the human PH alkaline/acidic scale the acid-mantle sweat perspiration is 4.0-5.5, surprisingly quite acidic. Human hands yield oils, sweat and water molecules, additional minor elemental combinants that may effect general long-term surficial rock structures.
Additionally, as a side note, various rock shoe rubber types have scalable properties (rebound resilience, abrasion, and hardness). For example, a rock shoe rubber might have a Hardness Scale (Shore A) factor 67-71+/- (or higher 76-80+/-), an abrasion factor variant (290-302), and general resilience or rebound variables (11-13% +/-). Most rock shoe rubbers vary in scale depending on its original designed purpose, edging, alpining, smearing, etc. Based on some known scalable factors it may be worth further discovery to determine applicable rock shoe pressure event factors placed upon various rock surface types.
In summation, the shorter the bouldering problem, or the shorter the rock climbing route (i.e Classic Crack at Broughton) the higher the incidence of long-term abrasion on the hand and foot holds. These events are somewhat compounded when a boulderer or climber uses or stands on a dirty surface (ground) or grimy crashpad. So, bouldering, due to its brief problem shortness factor (1-7 moves long) it tend to experience a higher degree of worn-ness of the rock surface. Long lead rock climbs (40' to 200' +) are much better situated in the respect that long-term abrasion is evenly distributed across the entire length of a given route, infinitely stretched when the route is multi-pitch. You might never see a wear factor on long multi-pitch routes like SE Face of Beacon Rock, for example. But, you will certainly see wearness factors on heavily traveled bouldering problems (i.e. at Carver), especially the short boulder problems.
Certainly its advantageous in all degrees to encourage the entire quantity of Portland's rock climbers (and boulderers) to distribute across the entire spectrum of climbing and bouldering sites, thus minimalizing the possible quantitative factors of surficial abrasion. This event is relieved by marketing informational guidebooks. Contrary to the often voiced ideology pressed by various entities who desire to 'herd' the outdoor rock climbing (or bouldering) public entity into specific climbing site cul-du-sacs, thus somehow limiting the public from enjoying a great variety of climbing sites (and protecting something else), carries the presumption that Portland's outdoor sports rock climber will 'decrease' in totality. Such is not the case, in quantity, nor in popularity. Our region has a surprising plethora of decently high quality, seasonally (and multi-seasonally) accessible, close proximity climbing and bouldering site opportunities of virtual unlimited scope. The enthusiastic interests of participants who enter the sport of bouldering/climbing at local indoor gyms (or through coordinated events in clubs or groups) all lead to a greater yearly expansion of the outdoor climbing and bouldering activity. One valid reason this sports industry experiences such continuous and advantageous growth is its being based upon worthy outdoor recreational qualities and values, and its those values that carry suitable capacitive rewards that meet the satisfaction of outdoor enthusiasts.