Talus Troglodyte… An American Pika Symbiont

In my experience, one of the more rewarding aspects of growing older occurs when some riddle of the past, which long-ago may have lacked enough contexts for clear understanding, is resolved through some current day observation.  A sense of accomplishment always accompanies connecting the two bits of knowledge… no different than when some broken household article is made whole again using an assorted screw or spring picked from the junk bin.

This happened in late September 2019 when visiting one of the large talus slopes near Wyeth, Oregon to re-install one of the temperature loggers I’m using to understand the existence of sporadic permafrost in the Columbia River Gorge.  Before leaving the site, I decided to simply sit for thirty minutes and listen for the call of the talus-dependent American pika, which I’d identified and recorded on the steep slope last year.  I heard no pika, but within two or three minutes a loud, repeating “churring” sound led my attention to a small bird darting in-and-out of the large talus rocks just upslope.   As the bird continued moving in-and-out of the moderate sized boulders, it descended nearer my position in what seemed an investigative manner.  Finally, and within 5 feet of my position, I was able to identify the ruddy-bodied, white-bibbed bird known as the canyon wren (Catherpes mexicanus), whose song for many of us is inseparably wedded to rocky American West canyon landscapes.   But while considering that this was the farthest west and wettest terrain I’d ever seen a canyon wren, a long past unresolved question broke free of the cobwebs, and was seemingly answered by the context of the bird’s behavior and geological habitat.  The old mystery was “why did early naturalists and avian taxonomists attach the name Troglodytidae to the family of passerine birds we now call wrens?

First, however, we need to look at the roots of this unusual word.  Troglodyte may have been first used in Europe during the Middle Ages to describe people who built their homes in association with cliff-side caves.  The word’s origin is from the Greek roots trogle “hole” and dyein “entering”.  Today, troglodyte yet describes people who inhabit beautiful ancient abodes carved into native Tuffeau stone (a type of sandy and chalky limestone deposited in shallow Cretaceous-age seas) in the Anjou Loire Valley of France.  The word was also adopted by early naturalists to describe creatures that relied on caves and concealing rock habitats for their living… and this included the wren family. 

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Figure 1.   A Tuffeau stone “troglodyte” dwelling built into quarry cliff-face in the Anjou Loire Valley of France.

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Wrens (family Troglodytidae) are a mostly new world group of birds that contains 88 species and 19 genera worldwide.  Only one species is native to Europe and Asia (i.e., the “old world”), which is called the Eurasian wren (Troglodytes troglodytes).  This namesake was perhaps earliest described and tagged “troglodyte” by the Swiss naturalist and polymath Conrad Gessner in his very important 1551-1558 Latin-language work Historiae Animalium. Later in 1758, Swedish taxonomist Carl Linnaeus formalized the name under the modern binomial Motacilla troglodytes, although this was revised to the current binomial by French ornithologist Louis Jean Pierre Vieillot in 1809.  Until 2008, the Eurasian wren was considered the same species as our own Pacific wren, at which time genetic and song evidence led taxonomists to separate Troglodytes troglodytes into three closely related species including the Eurasian wren (T. troglodytes), our west coast Pacific wren (T. pacificus), and  our east coast winter wren (T. hiemalis).

Why people from at least the early Renaissance applied the cave-dweller name to the Troglodytidae family became obvious as I continued watching the Wyeth canyon wren.  His vocation seemed entirely devoted to darting below the rocky talus surface and foraging the underworld for food.  Ornithologists have long documented that the bird’s sustenance includes insects, other arthropods, and possibly other small animals.  When done in one area, he would flit back to the surface, scan the surroundings, do a characteristic sweeping bob and beak-dip, call, and then dive back below the talus surface.   

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Figure 2.  Illustration and description of Eurasian wren (Troglodytes troglodytes) from Conrad Gessner’s pioneering 1551-1558 “Historiae Animalium”.

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Similar behavior was reported by Gessner and other early naturalists with respect to the Eurasian wren (Troglodytes troglodytes).  Like our very own Pacific wren, the species was noted in winter “emerging out of the thick bushes or thick branches to enter the small caves that form the holes of the walls”, as reported by the French naturalist Buffon in his 1756 publication “Histoire Naturelle”.   But Buffon also credited Aristotle with first recognizing the bird’s utilization of small caves and overhangs… this incredibly being from the fourth century BC.  Vieillot colorfully describes this same habitat preference in 1809, saying “The eloquent and profound historian of nature has rightly given them the name of Troglodyte, given to them by the ancients, and which paints their taste for small caverns, wall-holes, and generally all obscure places”.  My own experience with Pacific wrens mirrors this preference for sheltered and “obscure places”, as I sometimes note the tiny birds in and around outside firewood stacks seeking food and shelter during the cold winter months.  I even found one trapped inside my woodstove this past spring, which had probably entered the chimney in search of insects, but was then unable to ascend the smooth pipe and escape.  The wren’s innate attraction toward even man-made openings can spell its death… as this event almost showed.  Fortunately, my unreliably altruistic cat alerted me to the bird’s rustling among the cold ashes, and I was then able to return the tiny bird to the outdoors unharmed.  (*See the footnote at the bottom of this article for information relating to the hazards of uncapped and unscreened vertical pipes or birds).

The careful observations of Europeans beginning in the Greek classical period established the fact that the Eurasian wren is inseparably linked to rocky habitats for food, plus shelter from the sometime harsh northern Europe ambient environment.   Note that the word “habitat” simply refers to some specific environment, or set of physical and biological conditions, which certain life forms have adapted to.   Different habitats provide species with their own unique food sources, shelters from unfavorable ambient conditions (including predation, extreme temperatures, aridity, etc.), and optimal breeding conditions.  Cave and blocky-rock geologies such as talus are obviously one specific habitat type that many species have adapted to. 

In the habitat “food realm”, and as earlier noted, the early observers discovered Eurasian wrens foraging rocky crevices for invertebrates.  Recognition of this characteristic holds constant to the current day, and wrens worldwide are still known as mainly insectivores.  Though I have no direct knowledge of the Wyeth canyon wren’s diet, my somewhat extensive winter-to-spring ice crawler (grylloblattid insect) trapping work has yielded considerable information on the diversity of invertebrates that inhabit Columbia River Gorge talus rock environments.  This list includes millipedes, collembolans, flies, midges, several spiders, snails, slugs, beetles, ants, wasps, crickets, worms, silverfish, pseudoscorpions, snow scorpionflies, proturans, and ice crawlers.  The total biomass of these creatures is likely quite large, therefore representing a considerable potential food source for consumers working the subsurface habitat.  (Note:  all Gorge grylloblattid and by-catch data and specimens are in possession of the Oregon State Arthropod Collection in Corvallis, Oregon, and are available for study). 

Equally noteworthy with respect to the habitat “shelter realm”, the early observers noted Eurasian wrens huddled together in protected, collective roosts during particularly cold nights.  Similar observations continue to the present day with respect to our North American wren species, and 31 Pacific wrens were recently found huddling within a nest box during a cold winter night in the state of Washington.  Huddling is a behavioral adaption that allows tiny birds such as wrens and kinglets to conserve body fat, heat, and life itself, during the long and cold nights of winter.   Collective roosting and huddling can result in a 25% reduction in heat loss in the case of two birds, and a 33% reduction in the case of three birds, according to research conducted on goldcrests by Robert Burton.  Even given the utility of huddling behavior, Humphrey Crick found that goldcrests may burn-off a critically high 20% of their body weight on very cold nights in the northern end of their European range.   

With the especially high susceptibility of small organisms to hypothermia and subsequent death (due to their high surface-area-to-volume ratios), many have evolved the strategy of spending critical times (i.e., cold spells and nesting periods) in close proximity to caves and other temperature-moderated landscape features.  This is unquestionably the case with canyon wrens, as nesting has been observed in cliff rock crevices to take advantage of the favorable thermal environment, and also concealment from predators.  To the best of my knowledge, the scant research on canyon wren life history has yet to show that the birds roost (either collectively or individually) within such geologies for maintaining warmth during cold periods.  However, it seems likely that the behavior exists, since it is so common among other Troglodytidae. 

The main point of this little essay has been to simply profile the life of yet another talus symbiont that has adapted to the Columbia River Gorge’s low-elevation talus environment.  The canyon wren is another animal… like the American pika and ice crawler… whose existence is closely tied to the intensely non-linear heating/cooling mechanisms and resulting thermal diversities that occur within our low-elevation, talus-veneered mountain landscapes.  (For more on the origin of these mechanisms, see “Revised Origin of Cold Talus Habitats in the Columbia River Gorge and Implications for Dependent Species”.  Also see “Ice Mountain —  A Theory of Why Pikas Exist in the Columbia River Gorge” for earlier thoughts on the development of cold and warm talus habitats supporting pikas in the Gorge).

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*Footnote:  Open-topped, vertical pipes pose a tremendous threat to birds, lizards, squirrels, and other animals.  Once inside, birds are unable to fly out, and the smooth sides make climbing impossible. Ultimately, they suffer a miserable death from starvation and exposure.   Such hazards may be most apparent with respect to tubular fence posts, mining claim markers, storage tank vents, etc., but most of our homes are fitted with unscreened roof-top plumbing vent pipes, dryer vents, etc. that also trap and kill wild creatures.   Check your home and property, and make sure all pipes and vents are either capped or screened.  Please refer to the article “Death by Pipe” https://www.partnersinflight.org/wp-content/uploads/2017/03/DeathByPipes-final.pdf for more information.

Author: Steve Stampfli, White Salmon, WA, USA, stampfli@gorge.net Date: January 28, 2020

Revised Origin of Cold Talus Habitats in the Columbia River Gorge and Implications for Dependent Species

Author: Steve Stampfli, White Salmon, WA, USA, stampfli@gorge.net

Low-elevation talus slopes of the western Columbia River Gorge appear to be geologies that can sustain cold and possibly permafrost conditions usually found at either higher elevations or more northerly latitudes.  The formation of likely sporadic permafrost is due the unusual thermal behavior of blocky-rock deposits that cause them to lose heat in winter at a higher rate than heat can be regained during summer.  As a notable result, these cold geologies / habitats support populations of cool-loving and stenothermal animals including American pika and members of the Grylloblatta insect genus.  It is furthermore possible that the process has resulted in significant deposits of underground ice, which may constitute unknown water supplies important to human economies and aquatic life in the Gorge.

As highlighted in Ice Mountain —  A Theory of Why Pikas Exist in the Columbia River Gorge, the situation in the Gorge is not unique, as there are other geologies across the globe that display the formation of cold talus and potentially permafrost in areas that have annual average air and soil temperatures that are well above 0°C (32°F).  Based on extensive work to describe the phenomena at places like Creux-du-Van in the Jura Mountains of Switzerland, scientists have theorized that the creation of localized sporadic permafrost is a result of the “chimney effect” thermodynamic process.  But before examining that term, and whether it adequately explains the processes occurring in our talus slopes, a quick look at the term “permafrost” is warranted.

Permafrost

Permafrost is simply defined as a patch of the earth’s regolith that is frozen, and has been frozen for at least two consecutive years.  And to be clear, regolith is defined as the layer of unconsolidated rocky material including soil between the earth’s bedrock and its atmosphere or waters.

There are four main permafrost zones on earth:  a) zone of sub-sea permafrost; b) zone of continuous land permafrost; c) zone of discontinuous land permafrost; and d) zone of alpine land permafrost.   These delineations are shown on the below map taken from Pewe’s “Alpine  Permafrost in the Contiguous United States:  A Review”.   Cross hatched areas represent the zone of continuous permafrost, hatched areas represent discontinuous permafrost, and solid black color represents alpine permafrost.  The continuous and discontinuous permafrost zones occur well north of the states of Oregon and Washington, generally above 50° north latitude.  While frozen soil in these zones is generally dictated by proximity to the North Pole, alpine permafrost can form much further south, if at increasingly higher elevations.  These areas are mapped in Figure 1, and several patches of alpine permafrost can be seen in our area (i.e., near 45° north latitude) corresponding to Mt. Rainier, Mt. Adams, Mt. St. Helens and Mt. Hood.  It is generally assumed that permafrost in all three zones can only form in places where either high latitudes or elevations result in annual average temperatures of −2°C (28.4°F) or colder.

Figure 1.  Pewe’s map of permafrost distribution across North America.  See above paragraph for legend shading definitions. 

But not all patches of perennially frozen ground on earth are found in the zones pictured above, which are all proximate to the poles or at high elevations.  These outliers are lumped together into a fifth category, called sporadic permafrost, and occur on the equatorial sides of the earth’s bands of discontinuous permafrost, or locally below the elevations of alpine permafrost.

Formation of Sporadic Permafrost in the Gorge

The existence of currently active (as opposed to relict) sporadic frozen patches in areas with annual average temperatures above −2°C must be explained in all cases by mechanisms that cause a relatively higher loss of heat (i.e., cooling) from the blocky-rock feature to ambient environment in winter, than is gained back from the surrounding ambient environment (i.e., warming) in summer.  Perpetuation of even very small seasonal net losses over time can, therefore, result in landform temperatures that are well below annual average ambient temperatures, and even below freezing.  For these mechanisms to operate, however, there must be avenues for free air passage into the soil/rock mantle.  Indeed, I would predict it impossible for sporadic permafrost to develop in fine or mixed grained soils, or solid rock landforms.

To understand how this seasonal thermodynamic imbalance can arise in either cave or blocky-rock landforms, it is useful to remember a very simple maxim which applies to wintertime overcooling:  “hot air rises vertically as a gas, while cold air flows downward as a liquid”.  Both of these represent very efficient heat transfer processes occurring in winter.

Case 1.  The Ice Cave and other Topographically-Contained Landform Features

The simplest illustration of this maxim is what has been called the “Balch effect”, a process that operates in the case of a confined, downward-inclined earth opening.  This situation was perhaps first described by Edwin Swift Balch in his 1900 book titled Glacières, and is best exemplified in our area by the Trout Lake and associated Big Lava Bed lava cave systems.  During the coldest periods of winter (dominated by stable high pressure systems, clear nights and little regional winds), very cold layers of air exist at the land’s surface.  Once formed, this dense, stable, heavy air behaves as a liquid, and flows down-slope in a very non-turbulent manner perpendicular to landscape contours.  When this cold layer encounters any depressions in the earth surface (whether a broad open basin, confined cave, blocky-rock deposit, etc.), it flows in and displaces any air that is even minimally warmer, less dense, and therefore more buoyant.  This obviously causes the upward displacement of any warmer air occupying the depression, resulting in a temperature inversion (i.e., a layer of cold air trapped next to or within the ground).

Topographically-depressed reservoirs of cold inverted air may or may not be stable depending on the ambient surroundings and the nature of containment.  Inverted air masses, in general, are extremely stable as long as they remain “capped” and isolated from outside heating influences, whether caused by the rising of warm air (thermal cell convection), advection due to regional winds, direct conduction from the earth or atmosphere, solar radiation, air pumping due to barometric pressure changes, etc.  Taking the example of cold air trapped in a desert basin, the stable inversion can be rapidly “uncapped” during mornings by solar heating of the basin’s surface, which in-turn results in upward rising convection cells, mixing, and warming of the once stable and overly-cooled lower atmosphere.

The absence of such “uncapping” mechanisms in the case of the protected ice cave perpetuates the existence of inverted conditions and the reservoir of cold interior air.  Once emplaced during the coldest periods of winter, the stable layer can persist throughout the summer season, aided by the large thermal mass of bedrock, lack of solar inputs, minimal downward conduction of heat from the surface, and absence of upward mixing convection.   The same thing can be occur in other depressed landscapes with openings, including topographically-contained blocky-rock deposits.

Case 2.  The Talus Slope and other Topographically-Uncontained (Sloping) Landform Features

It is more difficult to explain how a similar imbalance might occur in sloping blocky-rock geologies, including talus slopes.  Such geologies are the second landform type seeming capable of forming cold temperatures and potentially sporadic permafrost at low elevations in the Gorge.  The cause of the winter vs summer heating imbalance in such landforms is more complex than in the ice cave, given the vast numbers of multi-level air openings.  The deposits are also generally sloping and uncontained, therefore, seemingly prone to rapid gravity discharge of cold and dense air (and excessive warming) during summer.

Chimney effect diagram

Figure 2.  Conventional “chimney effect” diagram from the Sébastien Morard, Reynald Delaloye, and Christophe Lambiel 2010 article in Geographica Helvetica titled “Pluriannual thermal behaviour of low elevation cold talus slopes in western Switzerland”.

A currently accepted explanation for the formation of “cold talus” and likely permafrost at the base of some blocky slopes is known as the “chimney effect”, explained in the earlier article Ice Mountain:  A Theory of Why Pikas Exist in the Columbia River Gorge.   In short, the chimney effect results in differential heating and cooling of the blocky-rock slope, driven by seasonal differences in temperatures inside vs outside the deposit (see Figure 2 above).  As a result of these temperature and therefore density differences, the theory predicts that relatively warm subsurface air “chimneys” up-contour to the top of the slope in winter, thus forcing the simultaneous suction of cold stable air into the base of the slope.  This action can result in the formation of unusual open tunnels where heated air is output from the top of the snow covered slope.  The rate of cold air inhalation is directly related to the temperature and density differential, thus the velocity and volume of air intake is highest when outside temperatures are coldest.  In summer, air flow direction is reversed, when cold air sinks and flow back out of the bottom of the slope due to its relatively higher density than the outside air.  As this occurs, an equal volume of warm air is presumably inhaled into the upper slope.  This is thought to result in winter overcooling, and perpetually cold conditions inside the lower base of the blocky-rock slope.

There is no question whether chimney action causes seasonal transfers of air and heat wherever there are underground spaces with multi-level openings (e.g., talus slopes, some cave networks, etc.).  On its own, however, the usual chimney effect description doesn’t seem to explain why the total slope heat loss during winter is higher than total slope heat gain in summer.  Superficially, it would appear that the heat content of cold air being drawn into the uncontained slope’s base in winter should equal the amount lost by the discharge of cold air from the base in summer.  However, as in the case of ice caves, blocky-rock slopes display heat gain/loss imbalances that can result in perpetual cold talus and permafrost.  The following two sections will attempt to describe how this might occur.

Local Observational Evidence

Two side-by-side thermodynamic processes appear to drive the very efficient loss of heat from uncontained, blocky-rock landforms during winter, both understood using the simple maxim “warm air rises up as a gas, while cold air sinks down as a fluid”.

The long-wave infrared (LWIR) images below illustrate recently observed surface temperature effects present on talus during both the summer heating and winter cooling seasons.  Both frames show the northwest facing flank of Shellrock Mountain, Oregon, lying near sea-level just south of the Columbia River in the western Gorge.

The following observations related to summer heating period are made after examination of Figure 3.  First, the drainage of dense cold air (blue color) from the slope is immediately apparent along the lower margins of the talus skirt.  (It is hidden below the slope transect on this image due to tree canopy interference).  Second, above the cold air vent, there is almost no overall bottom-to-top trend in summer surface temperature along the slope transect.  Third, there is little variability in slope temperatures, resulting in a fairly smooth temperature graph that lacks spiky bumps and dips.  Surface temperatures are limited within a narrow 1.7°C range.

     

Different observations are apparent during the winter cooling period, as illustrated in Figure 4.  First, and as expected, the drainage of cold air from the bottom of the slope is absent due to internal temperatures now being above outside temperatures.  Second, as also seen in summer, there is little overall trend in surface temperatures from bottom-to-top of the slope transect.  Third, winter surface temperature variability across the transect is high, as evidenced by the graph below the image that ranges between 3.9 and 7.0°C  (3.1°C range).  This observation is best realized when viewing the very spiky nature of the temperature graph.  Finally, the image does not show indication of the presence of large patchy warm air vents on upper portions of the unbroken talus plane.   This supports the contention that warm air is not being conveyed upslope and within the blocky-rock mass, as the chimney effect theory predicts.  While large warm air vents are present on the left side of the Figure 4 image, these vertically-elongated winter features are clustered at the bottom and middle portions of the talus mass, and not at the top of the slope.  The large vents shown occur at topographically-uneven faces of the slope, characterized by convex ridges and concave rills associated with past slope movements.  They are not, therefore, considered relevant to consideration of the chimney effect, or the theory currently offered.

The above observational evidence indicates that significant winter overcooling is being driven by the formation of a multitude of small vertically-rising convection cells originating within the talus, which occur across the entire breadth of the unbroken talus field.  The vertically-rising convection cells are indicated by the individual spikes seen along the winter fall-line transect graph.  Each spike likely represents a column of rising warm air that is very efficiently conveying heated air vertically-upward and out of the slope. By my calculation (and pending possibly unknown limitations of the LWIR camera’s resolution), the average on-ground distance between the presumed convection cells equals 16 feet.  This equates to a density of 170 convection cells per acre.

The winter image also hints that the vertically-rising convective heat transfers are coupled to vertically-downward fluid-like intakes of cold and dense winter air into the landform between convection cells.  These induction areas are likely indicated by the troughs seen on the graph.  The high cooling efficiency of this arrangement somewhat assumes that the closely proximate upward and downward trending air parcels do not significantly intermix either underground or above the surface.  During cold and calm winter weather  patterns, it may be possible that the convection cells persist in a confined upward direction well after they emerge from the talus surface, thus allowing the proximate downwelling of dense cold air with little intermixing.  If this is the case, the effect may be identical to the up-and-down convective movements of air parcels during thunderstorms, where there is little intermixing.

Assuming the above two linked mechanisms drive the primary winter cooling process, it is not likely that significant amounts of cold air are being inducted into the base of the slope, as the chimney effect model predicts.  Instead, it appears that the entire blocky-rock deposit is being cooled from surface to base, as one uniform mass, during winter.  If bottom-of-slope intake does happen, it would probably only be forced when a continuous blanket of snow is present, creating a closed conduit for the warm and low-density air being buoyed upward.

It is also necessary to touch upon why summer heating mechanisms are comparatively weaker than the cooling mechanisms of winter.  This is fairly easy to understand in the relatively simple case of the ice cave.  Once warm air is displaced by the down-gradient flow of cold air into the contained and “capped” underground cavity, the cold inverted air is very stable in temperature and volume.  In a relatively small cave, the only means of introducing summer heat and uncapping of the inversion would be via the very inefficient downward conduction of ambient heat from above.

The inefficiency of summer heating in a sloping blocky-rock landform such as a talus slope is, however, more difficult to explain than in the contained ice cave example.  The difficulty stems from the fact that talus deposits are inclined and lack the bowl-like topographic containment of an ice cave; therefore, any cold air reservoirs forming in winter above the bedrock surface would tend to flow out of the slope’s base in summer.  While this unquestionably occurs (see evidence of lower-slope cold venting in Figure 3), the fact that this does not result in a high degree of summer heating is likely because the sub-surface flow of the inverted air mass is greatly slowed by physical resistance within the porous talus.  This resistance is compounded by the long distance the cold subsurface air must follow from top to bottom of the talus slope interior.  The inverted air mass contained in the base of a cold talus slope, therefore, might be comparable to a perennial lake having a restricted overflow/outlet channel, which due to its configuration lacks the ability to rapidly drain, and is thus fairly stable in volume.

Finally, note that this same internal resistance is likely responsible for the earlier hypothesized low rate of inhalation of cold air into the base of the slope in winter.  It is presumably much more efficient that the intake of cold air occurs vertically and downward, and immediately proximate to the multitude of vertically-acting warm air convection cells.  A vertically downward pathway for winter air intake is logically the shortest, least resistant, and most efficient pathway.

Applied Engineering Evidence

Civil engineers working in northerly latitudes have long recognized that roads, pipelines and other structures built upon relatively warm permafrost are subject to failure upon melting of the permafrost layer and deflation of the local landscape surface.  Melting is a consequence of replacing native soil and vegetation layers with non-porous compacted earth and pavement, and therefore, loss of the temperature buffering and cooling mechanisms important to maintaining the permafrost layer.

To counteract the loss of permafrost after construction, D.J. Goering at the University of Alaska Fairbanks has experimented with systems known as air convection embankments for protecting roadways and other structures built on warm permafrost.  Such systems involve perching structures atop a layer of porous gravel or rock having low fines content and narrow particle size gradation.  In the beginning, such construction may have been believed simply a means of insulating the frozen ground surface from the summer’s heat.  Eventually, however, Goering came to realize that a passive refrigeration effect was largely responsible for maintaining frozen ground conditions in the underlying soil layers.

To understand the apparently passive cooling mechanism, Goering built an experimental eight-foot thick, unconfined porous rock embankment near Fairbanks, and laced it with electronic temperature probes placed in a three-dimensional grid pattern.  After monitoring the internal and external temperatures for two years, and then modelling the internal heat flows, he was able to decipher how ground temperatures at the base of the embankment were being maintained below freezing.  The experimental findings closely match the LWIR imagery observations and the ideas presented in the last section of this article.

The following quote from the 2003 paper titled Thermal response of air convection embankments to ambient temperature fluctuations, effectively summarizes Goering’s findings:

“During the winter, the embankment is cooled at its upper surface due to low ambient air temperatures.  If the cooling is strong enough and the embankment material is of sufficient permeability, natural convection of the pore air will occur during winter months due to the unstable pore-air density gradient that develops.  The convection can transfer heat upward out of the embankment at a rate that may be more than an order of magnitude larger than conductive heat transfer, resulting in greatly enhanced winter cooling.  During summer the pore-air density gradient is stable and convection does not occur. Thus the embankment acts as a one-way heat transfer device or thermal diode that effectively removes heat from the embankment and underlying foundation material during winter without re-injecting heat during subsequent summers”.

Diagrams showing the isotherm lines and convection cell boundaries discovered by Goering illustrate the internal processes likely responsible for over-cooling the interior of Columbia River Gorge talus slopes.  These diagrams are presented below as Figures 5 and 6.  The non-spiky summer surface temperatures earlier shown in Figure 3 are explained by the stable and laminar sub-surface thermal patterns depicted in the experimental embankment shown in Figure 5 below.  Likewise, the more spiky surface temperature range seen during winter in Figure 4 is explained by the formation of the vertically-oriented internal convection cells seen in Figure 6.

     

Conclusions

Recent results of the Shellrock Mountain LWIR imagery work, combined with experimental evidence reported by Goering in 2003, support the conclusion that vertically-oriented, cell-confined “pore air convection”, and proximate subduction of cold and dense winter air is responsible for the existence of cold and sometime frozen ground in open, blocky-rock deposits of the Columbia River Gorge.  Very significant temperature declines can occur within blocky-rock slopes and embankments within a period of a few days or even hours during cold periods. These rapid events represent periods of intensely non-linear cooling, and have a disproportionally large impact on ground temperatures when averaged over the year.  The experimental evidence also indicates that gravity-driven outflow of cold air from a slope or embankment base in summer is a relatively inefficient means of landform warming, which does not necessary result in the melting of permafrost.  Even lacking the topographic containment of an ice cave, the inverted cold air mass remains relatively stable within the sloping blocky-rock deposit during summer.  This is probably due to high internal resistance to summer gravity-driven outflow of the stable inverted air system, as it flows downward along the long talus slope / bedrock interface.

Given the likelihood that pore air convection is the main mechanism responsible for winter over-cooling and sporadic permafrost formation within sloping blocky-rock deposits, I suspect that the winter-time chimney effect can be viewed as an inefficient manifestation of pore air convection occurring under snow layers.  In such circumstance, the very efficient co-existence of upward trending warm air convection cells with side-by-side cold air downwelling is interrupted by the snow layer.  As warm air rises within the blocky-rock deposit and nears the rock / snow interface, it is forced to follow an upslope path through the porous rock just below the snow surface.  Perhaps more important is the fact that the volume of warm air displaced upward is not being directly replaced by cold downwelling air from the open atmosphere.   Instead, rising warm air trapped below the snow layer causes a slow suction of cold air into the slope via transfers through the snow layer, and into the base of the slope.  The resulting mixture of inside / outside air then moves upward below the snow / rock interface at a relatively low velocity.  The rate of winter slope cooling is, therefore, significantly retarded by a) the low volumes of cold and warm air that can transfer through the snow cover, b) the high flow resistance encountered by rising air being sucked upward within the porous rock deposit, and c) the fact that the external cold air and internal warm air are being constantly mixed within the porous slope just below the snow layer.

The above conclusions indicate that the creation of sporadic permafrost and periglacial landforms is most likely to occur in zones characterized by low snowfall accumulation and periods of cold winter temperature.   Such conditions were at a maximum in the late Pleistocene, some 16,000 to 20,000 years ago throughout the Columbia Basin of the Pacific Northwest.  During that time, climates were dominated by cold and dry continental air masses (high pressure systems), that blocked entry of wet maritime weather systems onto the continent.  There is also evidence that lesser such conditions existed into the Holocene period, and may be still present today, evidenced by sporadic permafrost scattered across the Pacific Northwest.  In the case of the western Columbia River Gorge, the occurrence of scattered permafrost can be partially attributed to the fact that the region exhibits large masses of porous talus occurring in low-elevation snow-free zones, which is favorable to efficient pore air convection.  Equally important, however, is the fact that dry and cold continental weather patterns are still very dominant aspects of our winter weather.  Each winter, we experience periods when calm and cold air settles into the Gorge from the east, resulting in prolonged periods of sub-freezing temperature.  These periods, which Goering has shown to have the ability to cause intensely non-linear cooling of blocky-rock deposits, must largely account for the occurrence of our cold and likely frozen blocky-rock slopes.

Finally, the apparent overwhelming dominance of non-linear winter cooling within blocky-rock landforms indicates that long-term plant and animal habitat temperature trends are not simply dictated by annual ambient temperatures, or even by annual high temperatures.  It is therefore impossible to conclude that simple rises in regional or global average temperatures can be directly correlated to an increased threat to populations of stenothermal talus or cave dwellers.  Instead, experimental findings reported in this article indicate that the long-term thermal stability of blocky-rock habitats is dictated by the number and length of periods when temperatures drop below specific levels.  This, of course, greatly complicates any attempt of forecasting long-term population trends or threats of species declines for organisms dependent upon such geological habitats.  This is not to say that such threat analysis is impossible for rock and cave dwelling organisms such as pikas and grylloblattids, but only that conclusive answers will likely depend upon multi-disciplinary efforts involving geologists, meteorologists, climate scientists, statisticians, biologists and physicists committed to the work.

Steve Stampfli

21 May 2019 at White Salmon, Washington

– END –

Stronghold of the Ice Crawler

Author: Steve Stampfli, White Salmon, WA, USA, stampfli@gorge.net

The occurrence of currently active geologic and weather processes that result in formation of both summer cold and winter warm temperature geological zones (and biological habitats) in Shellrock Mountain talus slopes is certain.   But in addition to that, it now appears possible that a second western Columbia River Gorge area could harbor several acres of relict periglacial terrain that dates back many thousands of years.  That seemingly bold statement is supported by growing biogeographic evidence.

Evidence of the second periglacial area arose via a March 6, 2018 email from biologist Jim Kirk, who had recently read the first article in the GorgeScienceShare blog “Ice Mountain – A Theory of Why Pikas Exist in the Columbia River Gorge”.   Kirk is an experienced field biologist who worked during the early 1980s describing the distribution of plethodontid salamanders in the western Gorge.  His email concluded with the amazing statement that he had trapped grylloblattid insects (ice crawlers) just above the Columbia River and west of Shellrock Mountain in February 1983… some 36 years ago.

It appeared that Kirk had discovered one of nature’s rarest and elusive insects.  But even more remarkable was the fact that the discovery was made far from their typical mountain, snowfield and glacial haunts, at an almost sea-level elevation in the western Columbia River Gorge.

Figure 1.  Recently molted immature ice crawler (Grylloblatta) from a lava tube cave near Mt. St. Helens in the state of Washington (photo courtesy of Joe Warfel).

~ The Ice Crawler ~

Ice crawlers are members of one of the world’s oldest insect orders, Notoptera, which date back 200 -250 million years to the Permian period of the late Paleozoic era.   When Notoptera first appear in the fossil record, the earth’s climate was typified by high carbon dioxide levels, and much warmer temperatures than today.  It was also a time when a huge amount of forest vegetation was being produced, and its carbon photosynthetically fixed and geologically sequestered.

The fossil record shows that early members of the order had two pairs of large wings that enabled them to travel widely throughout the hot and tropical forests, feeding on pollens from early conifers and other early plant types.  They filled a pollinator role in the primordial forests, much in the same role as today’s bees and wasps.  But then, a series of changes in the earth’s climate and biology occurred that would change the planet’s evolutionary path forever… the advent of flowering plants.

As Harvard biogeographer, writer and photographer Piotr Naskrecki wrote in his 2010 “The Smaller Majority” blog, “gradually, they (ice crawlers) disappeared from the fossil record. Strangely, there is not a single ice crawler known from the period after mid-Cretaceous. Their disappearance coincides roughly with the appearance of flowering plants, or angiosperms, and the nearly concurrent diversification of beetles and other plant pollinators. It seems that rather than allowing themselves to be outcompeted by this new army of more advanced plant-associated insects, the ancestors of ice crawlers found survival in a completely new lifestyle”.

Instead of being forced into extinction by the myriad new insect forms tailored to angiosperms, the ice crawler’s ancestors took advantage of previously unoccupied habitats that were forming on the then cooling earth.  These habitats amounted to the periglacial environments forming around the margins of glaciers and snowfields, plus the interior of frozen rock fields and icy caves.  In adapting to these cold and largely subterranean environs, the early Notoptera shed their wings and adopted a lifestyle based upon hunting other insects, and scavenging what food was carried into their range by wind and gravity.  Rapid decomposition and lack of inundation by fine particles in their new rock and snow haunts was not conducive to fossilization of their remains, hence the seeming disappearance of grylloblattids from the fossil record.

Today’s Grylloblattidae are a rare family of insects restricted to cold mountainous areas in western North America, and parts of northeastern Asia including Japan, both Koreas, China, far eastern Russia and south central Siberia.  As of 2018, the family exhibited just 33 species and 4 subspecies, within 5 genera worldwide. It belongs to the second-smallest insect order, Notoptera, along with the family Mantophasmatidae (rock crawlers).  All grylloblattid species are highly endemic, thus have very small geographic ranges (i.e., a median geographic area of only 179 square kilometers, or 79 square miles).  In North America, there are now 15 documented species and 3 subspecies, plus a number awaiting verification via physical and genetic analysis. North American distribution is limited to the states of Washington, Idaho, Montana, Oregon and California, and the provinces of Alberta and British Columbia.  (Note:  much of the technical information on grylloblattids presented in this article is from Schoville and Graening, 2013. “Updated checklist of the ice-crawlers of North America, with notes on their natural history, biogeography and conservation”).

The chief reason ice crawlers display such small endemic ranges and have such poor dispersal abilities is their evolutionary adaption to very narrow habitat temperatures (i.e., stenothermalism).  Almost all ice crawlers are found in habitats with rocky retreats that maintain steady cool temperatures and humidities throughout the year.  Fifty years ago, a pioneering grylloblattid researcher named Bill Kamp recognized that the cryophilic (i.e., “cold loving”) nature of the genus Grylloblatta along with its unusual distribution correlated with Pleistocene glacial advances.  He proposed that surviving populations would be limited to areas that were previously glaciated or at the edge of glaciers (i.e., periglacial environments) since the last glacial maximum some 21,500 years ago.  Ice crawlers are normally active above-ground during the night, but only when temperatures hover around freezing.  They show a preferred temperature range of 0-1° C.  The range associated with an undescribed species on Mt. Rainier, for example, shows acute temperature thresholds between -8.5 and 15° C.   This supports the colorful statement that human touch can transmit enough heat energy to kill the insects.

~ The Stronghold ~

Jim Kirk’s announcement of his 36 year old discovery was notable from the biogeography standpoint, since it was signal of yet another cryophilic and stenothermal organism being harbored in the taluses of the western Gorge.  Proving the continued presence of the organism would also support the odd probability presented in the first article that low-elevation permafrost conditions still exist hidden in the Gorge.

With a little research, I soon determined that there are several prominent entomologists in North America and northeast Asia who specialize in the study of ice crawlers, and who may be interested in understanding the significance of the animal’s occurrence in the Gorge.  One of these is Dr. Sean Schoville of the University of Wisconsin Department Of Entomology, who further specializes in the tools of molecular ecology.  Molecular ecology is the exciting, relatively new field that utilizes DNA analysis to unlock how new species evolved on our planet, and how they fit into the modern-day ecological framework.  Just as any of us are now able to use emerging genetics labs to uncover our own human history, scientists like Schoville use similar sequencing equipment to analyze insect DNA for understanding species evolution and ecologies.   (See https://www.biographic.com/posts/sto/bugs-on-ice for a well-written description of ice crawlers and the folks who study them).  Other prominent ice crawler researchers are located right here in Pacific Northwest, in the persons of Dr. Chris Marshall and Dr. Dave Lytle, both entomologists in Oregon State University’s Department of Integrative Biology.  This team recently uncovered two new grylloblattid species in the mountains of Oregon, including the snowfields around Mt. Hood (see this OPB Oregon Field Guide video segment .

After contacting Sean, Chris and Dave with details of my own work, and the report of Jim Kirk’s original discovery, all three agreed to help sleuth whether ice crawlers were indeed harbored in the Gorge, and if so what species are present and how they fit into the broader North American distribution.  In addition to these three, others who agreed to provide advice during the project included Jim Kirk, Dr. Scott Hotaling of Washington State University School of Biological Sciences, and Dr. Jeff Holmquist of UCLA Institute of the Environment and Sustainability.  The US Forest Service also agreed to become a partner via issuing a special use permit for grylloblattid collection activities, effective September 2018.

The very first visit to the site’s on-ground coordinates supported expectations of what I would find.  Most of the north-facing slope was dominated by well-sorted talus that was relatively free of fine-grained rock and soil particles.  Such “open” talus slope conditions seem prerequisite to free air exchange, and active slope cooling / warming mechanisms that can result in temperature-moderated habitats (see Ice Mountain article for description of Balch and chimney effects).  Infrared imaging currently being used at Shellrock Mountain is indicating that summer surface temperatures at the bottom of certain talus slopes are approximately 10° C cooler than temperatures slightly upslope.  Similarly during winter, mid-slope warm vents areas are being shown to have temperatures about 5° C warmer than nearby cold zones. The existence of habitats that display cold and hot zones in close proximity could be vital to organisms like ice crawlers, which are physiologically limited by both hot and cold extremes in summer and winter.  Importantly, LWIR imagery is showing that talus hot and cold zones can be only tens-of-feet of one another, therefore seasonally traversable by organisms with limited migrational ability.

But beyond the talus substrate, I noticed something related to the topography that I’d never seen before.  Kirk’s original trapping site and the surrounding thirty acres had somehow been shaped into a series of five, symmetrical east-west trending ridges and trenches.  The appearance was reminiscent of the artificial earthen structures built as fortification around hillforts and castles during Europe’s prehistory and Middle Ages (see Figure 2 and Figure 3 below).  If still present, Kirk’s anomalous low-elevation ice crawler population seemed to be harbored within a natural fortress comprised of a series of ramparts.  There was irony in the situation, since grylloblattids appeared to be taking refuge in a landform resembling the fortresses used by our own ancestors long ago for repelling invaders.  Of course, in the ice crawler’s case the refuge was likely providing stable temperatures in a larger world of much broader temperature extremes.  But that colorful wondering aside, the chief task for the moment was determining whether ice crawlers still occupied the site.

Figure 2.  Artificial earth ditch-and-rampart defenses from the Bronze Age at the Ipf Hill Fort, Bopfingen, Germany (from Dark Avenger at de.wikipedia ).

Figure 3.  Interior of 4th natural rampart at the “Stronghold” grylloblattid survey site, viewed from the east end (Stampfli photo).

The Columbia River Gorge grylloblattid survey was initiated on-ground in late October of 2018, and within one month the first ice crawler was trapped at the “Stronghold” study site.  This confirmed the validity of Jim Kirk’s historic observation, and happily signaled that this uniquely cryophilic (cold loving) and stenothermic (narrow temperature range) insect still inhabited the apparently ancient landform.

Sampling is on-going at the 30 acre site, plus some nearby talus slopes.  As of December 31, 2018, I had collected a total of 76 individuals for morphologic examination by Marshall and Lytle at OSU, and accession into the Oregon State Arthropod Collection.  Tissue samples for genetic analysis and species determination are also being forwarded by the OSU team to Schoville at the University of Wisconsin.  The western Gorge grylloblattid project is still in its early stages.  Therefore, the identification of what species are present is incomplete, as is understanding of the broader Gorge distribution and how Gorge species may relate to the higher elevation populations found on Mt. Hood, Mt. Adams vicinity, and elsewhere in the western US.

~ Periglacial Landforms in the Columbia River Gorge ~

There is no evidence that either continental ice sheets or Cascades Range alpine glacial conditions extended to low elevations in the western Columbia River Gorge during the height of the Pleistocene or later Holocene epoch.  The Laurentide ice sheet reached a point about 150 miles north of the western Gorge some 16,000 – 20,000 years ago, thus did not directly impact the area.  However, the massive ice sheet’s influence on western US climate, geology and natural history was enormous, given two primary factors.  First, the North American jet stream had become split, and the southern branch (and therefore the location of winter storm tracks) shifted south.  This southerly shift robbed the Pacific Northwest of its marine-derived moisture and moderated temperatures.  Second, due to the anticyclonic (i.e., clockwise) direction of winds that prevailed over the ice sheet, easterly “continental” wind patterns accompanied by dryness and cold became dominant (see Kathy Whitlock’s 1992 paper entitled “Vegetational and Climatic History of the Pacific Northwest during the Last 20,000 Years: Implications for Understanding Present-day Biodiversity”).  As a result of these two factors, plus the already cooling global climate, processes that supported the formation of periglacial steppe environments and landforms became dominant in the Pacific Northwest interior at the end of the Pleistocene.  From the geomorphology standpoint, mechanical weathering processes such as the freeze-thaw responsible for the formation of fractured rock deposits and localized permafrost conditions would have become very active during this epoch and later glacial re- intensifications during the Holocene.

Perhaps the most obvious example of a once large-scale, likely inactive periglacial landform in the Gorge is found in the Catherine Creek area east of Bingen, Washington.   This location exhibits large areas of what has been termed “fractal patterned ground”, and also what I believe to be a dormant or fossil rock glacier.  This feature would have once transported rock in an icy matrix down to the Columbia River from the 1,000 foot elevation scarps to the north.  Similar large-scale, but now likely dormant or fossil periglacial features can be witnessed just across the river near Mosier, Oregon.  These mostly unstudied and poorly understood landforms will be the subject of a future blog article.

There are at least two examples of relict, likely active periglacial landforms in the western Columbia River Gorge.  Both of these occur within the 20 mile reach between Shellrock Mountain and Multnomah Falls.  Not surprisingly, this is also the reach that displays anomalous low-elevation populations of the cold-adapted and stenothermal American pikas and grylloblattid insects.  The first example is the Shellrock Mountain talus slope described in the Ice Mountain article.  The second likely active feature is the subject of this current writing.

Over the course of several visits to the Stronghold site, I tossed around various explanations for how the linear ridge-and-trench (rampart) topography could have come to exist.  The question was also posed to a few professional geologists for their interpretations. To enable better examination, it was apparent that having a broader “looking glass” via the use of lidar imagery would be helpful.  Thanks to assistance of Hood River County GIS Coordinator Mike Schrankel, the below lidar image was soon acquired.

Figure 4.  Lidar imagery of suspected Pleistocene and Holocene pro-nival ramparts, being overtaken by more recent alluvial, landslide and talus fans, west of Shellrock Mountain, Oregon.  These ramparts represent at least one of the landforms now known to support grylloblattid (ice crawler) populations in the western Columbia River Gorge.

The first of the eventually rejected explanations for formation of the landforms shown in Figure 4 is some type of bedrock-source movement, such as rock falls, rock avalanches and/or translational rock slides.  The source of material for all of these mechanisms would principally be mechanical weathering of the currently 800 foot tall head scarps (cliffs) uphill of the features.  Typically, as bedrock scarps mechanically erode, they gradually shed rock, and “march” backward and usually upslope (in this case, to the south and toward the bottom of the image).  This results in stable, tapering talus and debris fans, and not trenches and ridges.  This holds true in all climatic and geological environments I am aware of.  It is also true that such large-rock dominated fans display high internal friction, and are not prone to rotational debris slides (slump-type failures), which could theoretically result in irregular ridge-like features on receiving lower slopes.  Note that the rampart features are mostly composed of well-sorted talus, and not the very mixed materials observed at surrounding fans of alluvium and landslide debris, which conceivably could be prone to mass movement and irregular downslope deposition.

A second currently rejected explanation of the Stronghold’s ramparts is that they were formed by a common periglacial process known as thermokarst deflation.  Just as “sinks” or depressions are formed in limestone terrains due to the dissolution of soluble bedrock from below, depressions can also be formed in permafrost terrains via the melting of subsurface ice.  Elongated and concave (dish-shaped) thermokarst depressions can form at the base of frozen talus slopes, when their basal ice lenses disappear during persistent warm periods.  I have found likely examples of such thermokarst at the 4,000 foot elevation on the Washington side of the Columbia River.  While the Stronghold seems to exhibit characteristics favorable for the formation of permafrost and the accumulation of subsurface ice, it is not clear why a series of parallel thermokarst depressions would result upon thawing.

The third hypothesis that might explain the origin of the Stronghold’s talus ramparts relates to the series of glacial outburst floods that occurred at the end of the Pleistocene epoch some 13,000 to 15,000 years ago.  Although far-fetched, the hypothesis is interesting to consider, and could deserve more careful consideration by geologists.  Many travelers on I-84 westbound have noticed what looks like a westward trending side canyon on the south side of the interstate west of the Shellrock area.  This appears to be an ancient 3.8 mile long high-water passage “channel” formed during the floods.  The channel passage climbs 400 vertical feet to a crest of 570 feet before dropping back down to the Columbia River.  At least one of the flood events may have reached an elevation of some 750 feet in this reach of the Columbia, thus easily filling (and perhaps creating) this channel passage via massive river erosion.  Interestingly, this projected flood crest is at, or a little below, the elevation of the Stronghold ramparts.  It is therefore conceivable that large blocks of ice floated by the floods could have bulldozed deep gouges into the talus dominated shoreline, and resulted in the striated surface seen on the lidar image.  Although it is hard to flatly reject the possibility that ice age floods bulldozed the Gorge’s Pleistocene shorelines, it is unclear how such gouging action could have resulted in such a well-spaced series of relatively uniform gouges.

The fourth possible, and I think most likely explanation of the Stronghold terrain, is that it represents a series of relict periglacial landscape features known as pronival ramparts.  Such ramparts are simply ridges of moderately well-sorted talus debris that was originally shed from an overhanging headwall, landed atop a steep snowfield, rolled down the snow/ice slope, and was finally deposited at the base of the snowfield.  Sorted talus is a material that geologists typically see just below headwall sources, so the first clue to the rampart’s periglacial origin is its anomalous location well downslope of the main cliff pediments.  Pronival ramparts account for such anomalous location of graded talus given the fact that the snow field ramps act much like a combination “grizzly screen /conveyor belt”, which “screens”-out smaller particles as the mixed material works its way down the snow slope.  Eventually, only the larger rocks find their way to the base of the snow field for final deposit.  Rock sorting on snow slopes is therefore very similar to that occurring on an angle-of-repose receiving slope, where fine particles (the lesser volume, in this case) settle to the slope first, while larger diameters (the bulk of the volume) roll or slide to the bottom.  Here they can form rampart features in straight or arcuate ridges, well downslope of any cliff base talus accumulations.  Note, however, that rock-on-snow transport can occur at low gradients, and the eventual point of deposition can be anomalously far downslope.

Figure 5.  Genesis of a pronival rampart (from http://www.landforms.eu).

To enable formation of multiple and large pronival ramparts in the western Gorge, the presence of intermittent perennial snowfields would have been necessary, perhaps beginning in the late Pleistocene and ending as recently as the Little Ice Age (about 1900 AD).  The possibility is not hard to accept when realizing that deep depths of hard firn or ice pellets covered the Oregon side of the western Gorge as recently as the winter of 1884-85 (near the end of the Little Ice Age), and again 1922 (see discussion and historic snowbank photo in Chapter 4 of the Ice Mountain blog article).  It is logical to assume that even those recent and relatively small snow or ice fields could have lasted throughout following summers, given up to 20 foot depths of ice and the high degree of topographical shading on the Oregon side of the Columbia.

But what could explain the multiple parallel ramparts at the Stronghold site, instead of there being only one?  One idea is that the ramparts were deposited sequentially during the series of cold climatic periods that occurred in the late Pleistocene and Holocene.  As episodic cold periods favorable to mechanical freeze-thaw action ensued, the hard snow ramps necessary for rampart formation may have formed and lasted for decades or even centuries. They may have also been insulated from summer melting by veneers of insulating rock and soil, much as can be witnessed protecting the rock-veneered glaciers on Mt. Hood today.

It might, therefore, be reasonable to hypothesize that rampart formation corresponded to the major periods of cooling that began as early as 20,000 years ago, and ended as late as 1,900AD.  If glacial flood elevations did not rise above the lowest rampart (and thereby wash it away), it is conceivable that it was deposited during the first Cordilleran glacial maxima event (Evans Creek Stade) some 17,000 -22,000 years ago in the late Pleistocene.   Following this, a subsequent rampart could have formed during the second Cordilleran glacial maxima known as the Vashon Stade, some 14,000 – 14,500 years ago.  Following the end of the Pleistocene (and glacial floods), the Pacific Northwest entered a 3,000  year span of warming during the early-mid Holocene epoch (Holocene Climatic Optimum) between 6,000 and 9,000 years ago.  At the end of this warm period, the region experienced a new series of recent cooling periods that could correspond to subsequent rampart depositions.  A first Holocene “new glacial maxima” period occurred some 5,000 -6,000 years ago, which was followed by a second such period 2,500 – 3,500 years ago.  A third and final Holocene glacial maxima, known as the Little Ice Age, started in 1,350 AD and lasted until the current era of glacial retreat began in 1,900 AD.  That said, there seems no current way to determine ages of the five ramparts, and thereby sequence their formation.   Sequencing might be possible if a person had the ability to date the cliff and talus features in consideration of the past climates.

While the north and west slopes of Shellrock Mountain likely display currently active periglacial processes and permafrost, the Stronghold situation is less certain.  The strongest evidence in favor of permafrost at the site is biological, and the fact that the landform supports a population of insects that are believed to have dispersed along the advancing and receding margins of the Pleistocene continental ice sheet.  Additionally, these animals display physiologies that require current day habitats that never stray far from the freezing point.

Acquiring physical evidence of permafrost conditions within the Stronghold ramparts is in its early stages.  So far, fall-season LWIR imagery has indeed shown anomalously cold zones at the bottom of the trench features.  Additionally, the persistence of tiny interior patches of snow was noted during late fall 2018.  Both of these could be evidence of active Balch and chimney-effect processes.  Better knowledge will be available in the future, given the fact that sub-surface temperature loggers were installed in fall 2018 to track bi-hourly temperatures for the next several years.

Acknowledgments:

I thank Jim Kirk, Sean Schoville, Chris Marshall, Dave Lytle, Scott Hotaling and Jeff Holmquist for their considerable technical, curatorial, lab, and advisory work  related to this project.  I also thank Steve Castagnoli for providing use of the entomology lab at OSU’s Mid-Columbia Agricultural Research and Extension Center in Hood River, and Hood River County GIS Coordinator Mike Schrankel for producing lidar images .

Comments on this article can be posted below, or via email at stampfli@gorge.net.

Mouseland

Author: Steve Stampfli, White Salmon, WA, USA, stampfli@gorge.net

Cover of 1901 book by Edward Earle Childs

 

When U.S. Captain George B. McClellan traversed Washington’s Cascade Mountain Range in 1853 (nine years before he would briefly serve as general-in-chief in Lincoln’s Union Army), his wagon train was well equipped with a trained naturalist, other scientists, artists, interpreters, and native guides.  The main purpose of his “Northern Survey” was to locate a possible transcontinental railroad route, but a secondary reason was simple scientific and ethnographic exploration of the American west.

The McClellan Survey began at Ft. Vancouver, Washington on June 15, 1853, and worked its way up the Columbia River until veering north into the Cascade Range west of Trout Lake, Washington.  In mid-August, the expedition encountered a curious landscape dominated by a long series of lava caves, natural bridges and rough-bottom trenches, stretching along a 12 mile line from the Big Lava Bed eruption cone down to the present site of Trout Lake, Washington.   Modern day travelers retrace the route via driving State Highway 141 west of Trout Lake, merging onto USFS Road 24 along Dry Creek to Peterson Prairie, then continuing along roads 60 and 66 to the South Prairie vicinity.  Along the path are found the current day “Trout Lake Ice Cave” and “Natural Bridges” waysides.

During the Holocene epoch (6,200-8,200 years ago) lava eruptions from the Big Lava Bed cone flowed east-northeast toward Trout Lake.  During one such flow, the surface cooled and crusted over (much as a cold mountain stream might freeze-over from the top), thus creating a sub-surface conduit carrying the stream of molten rock.  Once the eruption stopped, the underground conduit drained of lava, thereby creating a long vaulted underground passage.  In the centuries that followed, some long sections of the passage collapsed forming open trenches with boulder-strewn floors.  Other short sections remained standing as “lava bridges”, while other longer sections of standing conduit resulted in what we now term “lava caves”.

When arriving in the region, the 1853 expedition’s first source of knowledge would have undoubtedly come from their native guides, plus contacts they had with the native people who inhabited the high country around Mt. Adams in summer.  As a result, the expedition was able to describe the area traversed, and record local American Indian mythologies that told of the origins of the terrain.  The following transcription is one such origin myth, copied directly from the 1854 Annual Report of the Commissioner of Indian Affairs to the US Congress:

“In descending the valley from Chequoss (note, historians conclude this is likely Indian Heaven), there occurs beneath a field of lava a vaulted passage, some miles in length, through which a stream flows in the rainy season, and the roof of which has fallen in here and there. Concerning this, they relate that, a very long time ago, before there were any Indians, there lived in this country a man and wife of gigantic stature. The man became tired of his partner, and took to himself a mouse, which thereupon became a woman. When the first wife knew of this, she was, very naturally, enraged, and threatened to kill him. This coming to the man’s knowledge, he hid himself and his mouse-wife in a place higher up the mountain, where there is a small lake having no visible outlet. The first woman, finding that they had escaped her, and suspecting that they were hidden under ground, commenced digging, and tore up this passage. At last she came beneath where they stood, and, looking up through a hole, saw them laughing at her. With great difficulty, and after sliding back two or three times, she succeeded in reaching them, when the man, now much alarmed, begged her not to kill him, but to allow him to return to their home, and live with her as of old. She finally consented to kill only the mouse-wife, which she did, and it is her blood which has colored the stones at the lake. After a time, the man asked her why she had wished to kill the other woman. She answered, because they had brought her to shame, and that she had a mind to kill him, too; which she finally did, and since when she had lived alone in the mountain.

Another story about the same place is to the effect that it was made by a former people called the Seaim, a name corresponding with the jargon word for grizzly bear. The mouse story seems to be interwoven with the Klikatat mythology; for, besides the name of this place, Hool-hool-ilse, (from hool-hool, a mouse,) one of the names of their country, is Hoolhoolpam, or the mouse-land. This is given to it by the Yakamas…”.

Consideration of this historical source leads to the remarkable conclusion that the Yakama people of the mid-1800s most associated their allied Klickitats with a land dominated by the presence of some small animal, whose common name was translated by expedition members to mean “mouse”.  But was the land’s ubiquitous namesake truly a mouse, or even a member of the rodent family?  Or, given all the verbal and written translations and transcriptions involved in capturing the archetypal myth, did the expedition err in nomenclature?

It is certainly true that many rodents live in association with blocky rock environments like collapsed lava tubes, lava bridges, lava caves, lava plains, mountain sides, and talus slopes in the Pacific Northwest.  Rodents found in such areas include marmots, pack rats, chipmunks, ground squirrels, deer mice and others.  But to anyone who has spent time along this section of the McClellan Trail, it is obvious that Mouseland (hoolhoolpam) must instead be reference to the American pika.  Evidence of this is expressed by the currently high concentration of these members of the rabbit order (Lagomorpha) that inhabit the area, plus the fact that many Mouseland cave names reference this very visible and audible animal.  Current day place names include “Pika Here Cave”, “Pika Ice Cave”, “Squeaking Pika Cave”, and even “Chubby Bunny Cave”.

Along one lower reach of lava trench separated by bridges and caves, I have noted pikas in nearly every trench section, often in close proximity.  Pikas are territorial and usually widely dispersed on open talus, but perhaps the many deep trenches separated by basalt walls and rubble results in sufficient isolation without the usual distance seemingly required on open talus slopes.  As is often the case, perhaps “good walls” make “good neighbors” in the pika community.  Overall, my informal surveys have recorded the animals along at least half of the Mouseland reach, from 2400 to 3000 foot elevation.

Pikas, like all organisms, are subject to strict habitat criteria, including specific temperature ranges.  Their temperature tolerances are likely narrower than many other mammals, simply due to the fact that early members of their family (Ochotonidae) evolved in association with highly buffered temperature environments, typified by natural cooling and heating mechanisms (e.g. Chimney and Balch effects), constancy of the earth’s heat, plus the insulation afforded by winter snow cover and blocky rock deposits.  There is a huge metabolic efficiency advantage bestowed upon animals that can evolve in association with such environments, given the fact that the calories normally required for keeping warm and cool can be devoted to other important life activities such as acquiring food, reproduction, resting, reflection, and even play.

The drawback of genetic adaption to a narrow physical environment (i.e., habitat) is that it means such organisms are unable to venture far from that physical range.  Thereby, a state of what’s called “endemism” comes to exists.  Endemism is defined as a species’ ecological and genetic state being unique to a limited geographic location, or habitat condition.  Such species display relatively small geographic ranges consequent to their highly specific habitat requirements, and inability to migrate far from their “islands”.  Some highly endemic species such as ice crawlers (or grylloblattids) have very small species distributions, many being less than 100 square miles.

All of this leads to the difficult question of whether seemingly protected but narrow temperature range (stenothermal) organisms like pikas are at greater risk of extinction due to global warming than wider temperature range (eurythermal) organisms, such as tree squirrels.  On one hand, the cave and rock dwellers exist in a very stable temperature controlled habitat that is highly “decoupled” from ambient conditions at the earth’s surface.  It’s logical to assume that these sheltered but temperature-limited organisms can survive regular, short-term climatic cycles in place, perhaps better than more eurythermal forms.  On the other hand, if these short-term cycles of variability end-up trending toward consistently higher ambient temperature norms, this could result in a small but significant change in the subsurface environment, and be enough to put highly sensitive endemic and stenothermal species like pikas and grylloblattids at an even higher risk of extinction, especially since migration to new “islands” of suitable habitat is nearly impossible.