Sunday, November 21, 2010

11-19-10 Gale River Trail: Soil Development and Plant Succession On an Older Landslide Track.

On my way to the Gale River Trail on Friday morning (11-19-10) I was momentarily caught in a "white out" caused by a slow moving snow squall near the north end of Franconia Notch that created a magical world of light feathery snow that fell for 5 during which I felt as though I was caught in a toy globe that you shake and it produces a blizzard. It mantled everything: the highway, cars, and the woods along the road. A freakish part was that one minute I was driving in it and then it was gone, like a dream. Suddenly the sky was blue with sun poking through last remnants of clouds. The intensity of the squall was barely evident just a few miles away.

On the trail I was happy to have the dusting of snow as it highlighted details in the landscape and accentuated the late fall colors. At the same time I was hoping there weren't any hunters in the vicinity who might be using the light snowfall to track deer.

These are glacial erratics sitting just a few yards from the trail that are quite large and practically invisible when leaves are out.

First Crossing. The Gale was up a few inches, enough to get my feet wet on this and at second crossing. The US Forest Service is getting set to relocate the Gale River Trail completely to the west side of the Gale River eliminating the two crossings which present severe hazards after heavy rains and during the Spring run-off, particularly.

After the last crossing on the Gale River the trail climbs more steeply up into the steep-sided valley between the Twin Range and the Garfield Ridge and enters this sanctuary that's far enough back from highway and human habitation to fall completely under the forest's spell, the chorus of river, wind and birds, and a wonderful, infectious timelessness.

It's 3 miles from the trailhead to this tilting boulder that marks the area of the 1954 landslide where my small research site is located. This was my first visit in several months. I've timed it to take measurements before the soil freezes and the snowpack begins its yearly cycle. I picked a perfect day, it turned out, as it was cool and the light, with thin clouds, was flat and perfect for taking photos.

The next 9-10 photos might seem meaningless. I've included them as time-bound documents of the area where a mass wasting event occurred 66 years ago and where I'm researching soil development and revegetation (plant succession) along the path of the disturbance that was a major landslide. The slide stripped away the vegetation and top soil, leaving the area denuded as a glacier might. The research hopes to define a precise time that it takes a disturbed site to return to an optimal equilibrium or "steady state" (sometimes referred to as "climax"). I'm using two "control" sites. One of them is in Glacier Bay, Alaska, and was researched back in 1966 by a team of scientists under R.P. Golthwait. Their results were published as Soil Development and Ecological Succession In A Deglaciated Area of Muir Inlet, Southeast, Alaska (available through Goldthwait Polar Library, Ohio State University, Columbus Ohio, 43212). Fiorenzo Ugolini was the soil scientist on the team and wrote the chapter on soil development. I'll be collecting data at a second "control" site, a slide that came down during the 1938 hurricane, that's similar in exposure and altitude to the Gale River site. I'll write more about that later.

The above photo is looking up across study plot #1 in the direction from which the land slide descended.

This is a diagram of the slide looking north. The slide was about 300 yards long from the point where it broke off Garfield Ridge and traveled downslope to the wast bank of the Gale River.
At the river my theory is that the slide made a sharp turn once it got into the river bed and flowed down stream. It's likely that more than half of the debris from the slide landed in the river and some may have made it across. Whatever landed in the river was swept downstream. However, an enormous amount of debris, including boulders, sand, and gravel, spread out on the west side of the river in a football field-sized area to a depth of 6 0r 7 feet. Tree trunks including the roots were caught in the rubble. The Gale River Trail relocated itself as hikers, confronted by the slide track, threaded their way around the boulders and across the vast open area. Hurricane Carol was the weather event connected with the slide. The hurricane surged on a northerly course through New England on August 31, 1954 quickly dumping several inches of rain in the mountains. It's timing, path and force was nearly identical to the historic September 13, 1938 Hurricane that caused dozens of major landslides and destroyed millions of trees in the White Mountains. (Interestingly, Hank Parker, who worked in the huts in the 1940s and who was at the reunion at Madison Springs Hut on August 30th, told me that he remembers a slide track from the 1938 hurricane that was located slightly uphill close to, and parallel to the 1954 slide track from Hurricane Carol.)

This is a photo taken in November 1968 of the bottom area of the slide looking from south to north. I've written about the research site in several articles (2-14-09, 7-10-09, 9-5-09. 4-24-10) but I'll include this photo again and the one below to save the trouble of looking through the past articles. This photo shows evidence the slide curved into the river bed and headed down stream just the way the avalanche in Ammonoosuc Ravine did last February (2010). It left behind massive boulders that can be seen slightly downstream. The white arrow points to the "tilting boulder" that I sometimes use as a desk and table. Just for reference: this photograph shows the slide 14 years after the mass wasting event occurred. The extent of soil development and re-vegetation can be seen.

This is a photo of the slide taken five years later in November of 1973, 19 years after the slide, and shows the upslope portion of the slide, with its length and width and the extent of the re-vegetation. The area just behind Ken Olsen is where study plot #1 is located (what's depicted in the photographs from 11-19-10). It's probable that the landslide had a more destructive impact on the forest ecosystem that existed here prior to the hurricane then most other disturbances that can impact a forest ecosystem, even more than fire. The highest cost of the slide to the ecosystem is the nearly total loss of nutrient. Clear cutting, or even an extremely hot wildfire, would leave some nutrient.

In 1973, nineteen years after the slide, the re-vegetation is occurring along the edges of the slide and close to the bed of a small stream that drains the slide. The vegetation is comprised of several shade intolerant species that were present in 1968 including birch, alder, pin cherry, quaking aspen, and balsam fir. It would be impossible to estimate the biomass or basal area of the vegetation from the photo, however we can conclude that the numbers would be low compared to the ecosystem that existed prior to the slide.

This is a magnified view of the above photo from 1968 showing what the area in Plot #1 looked like 14 years after the landslide. In the upper left hand corner you can see tree stems, limbs and roots stacked in rows along the northern edge of the slide track left there by the slide on August 31, 1954. These represent a small percentage of the trees the slide transported. Most of the debris, including tons of vegetation was carried downstream by the river. On July 10, 1885 when the famous Cherry Mountain slide occurred, Oscar Stanley, a witness, said he felt the ground shake and "when I saw the slide it was full thrity feet high, the front of it rolling over and over as it moved." (Flaccus, 184). The speed of that slide was estimated to be 23 mph. On August 31, 1954, Ben Bowditch, a croo member at Galehead Hut, was packing up the Gale River Trail around 3 pm and said he heard a roar, looked up to see a wall of water descending towards him and had to hold onto a tree for atleast an hour while the water surged around and that was carrying whole trees and boulders from the slide site.

I magnified the photo to better show the extent of soil development and plant succession on the levelest part of the slide. Moss is growing in areas between the boulders and, in additon to moss, plants visible include alder (A. rugosa & A. crispa), balsam fir (Abies balsamea), Red cherry (Prunus pensylvanica), aspen (Populus temuloides), and white birch (Betual papyrifera var. cordifolia). These are shade intolerant species (meaning they thrive in direct sunlight) and are often found growing in disturbed sites such as clear cut and burned over areas.

This is another photo of plot #1. I'm currently working on determining the biomass and basal area. It's extremely tedious work and it easy to get distracted so I alternate between doing vegetation measurements and soil depths by hand. For the soil measurements I use thin, solid plastic wands (low impact) to measure soil depths at 1 meter intervals on an east-west transect. A random, secondary transect runs perpendicular to the primary transect. I rely on the local weather station in Twin Mountain to track precipitation and mean temperatures that are adjusted for altitude (2785'). I also plot diurnal-nocturnal temperature fluctuations.

Plot #1 has the small stream that drains the slide track running through it on a diagonal course. Vegetation in the plot is dense along the stream bed but less dense in most other areas of the plot. The above photo is of the west side of the stream in an area of the study plot where the vegetation is of median density. The soil depth here is above the mean and is a brown podzol (also referred to as spodosol) with a thin clay horizon. It is a typical boreal forest soil where the climate is cold and damp. It's acidic due to the granitic parent material from which it evolved. The top horizon has a high humus content. The depth of the soil in the area of the photo is 6.5 inches (16.5 mm) a little deeper than the median in this plot due largely to increased vegetation along the stream, a level slope, and dominance of deciduous birch and striped maple trees that provide leaf litter.

This is another photo of typical terrain in plot #1 for soil measurements showing upended trees and small diameter balsam fir that grow in dense clumps on the steeper slopes.

The Soil development formula is S (soil) = f (time) cl (climate) o (organisms in soil) p (parent material) and r (relief or degree of slope)(Ugolini, 30). In the formula soil, S, is the dependent variable and cl, o, p, and r are the independent variables. In this case the dependent variable, the soil, is being expressed quantitatively as a function of time so the fancy research terminology is "chronofunction" (meaning function of time) (Ugolini, 30). Evaluating the role of time is best where the history of the system is known as here where we have the exact date and time of the primary disturbance.

This is the northern edge of the slide track near the bottom of the slope that faces east. The vegetation here is not representative of the entire study plot and the soil reflects the difference in the top most horizon which is thinner in this area than the rest of the plot.

The total leaf litter accumulation is .5 inches for November 2010. It litter appears to be heavily compacted by recent rains but had been heavily compacted earlier by severe winter storms in February 2010. The slope in plot #1 goes from level and then rises steeply upslope. It faces the east so it gets a lot of sun but also gets the brunt of storms like the one last February that came in from the east. Snow depth in mid-winter in this plot reached 88 inches in late February 2010. The snow had a high water content. I hypothesized that spring run off from the heavy snows may have caused "slush flows" on the steep pitch above the study plot that may have taken leaf litter from the forest floor as they descended downslope. The slush flows are part of the hydrological cycle as well as a form of nutrient transport. Landslides are a from of "mass wasting", the downslope movement of soil, rocks, etc. due to gravity. It's also a form of of fluvial denudation, the normal aging process of land forms and collapse towards the gravity "ideal" of the perfectly level plain. To some degree landslides are also part of the large hydrological cycle as water is an intrinsic participant in landslides and involved in transport of nutrients both in and out of ecosystems.

One of the best sources of info on White Mountains slides that I know of is Edward Flaccus' 1958 Appalachia article White Mountain Landslides (Appalachia December 1958, 175-191) in which he presents exhaustive data on more than 500 slides that occurred in the White Mountains between the late 1700s and 1957. Of the 540 landslides listed, Flaccus was able to date 135 slides to the year, 127 to the month, and 123 to the day. In the case of the 1954 Gale River slide we have the day and the hour the slide occurred.

Looking east towards the Gale River Trail and the river from the western edge of Study Plot #1.

Flaccus reported that all the slides of which the day's date are known "occurred in connection with heavy rain. Large numbers have occurred during heavy general storms, especially those of the tropical-hurricane type, but there have been a number of occasions on which more localized rains of the summer-thunderstorm kind have been involved. All slides dated at least to the month have occurred in the period of June to November. There are no records of any occurring in the months of snow-melt and spring rains (March to May). Also, all the November slides, with one exception, are attributable to a single storm (November 3-4, 1927) occurring very early in the month. The frequency by months for the period is as follows: June, 15 slides on 5 different days; July, 2 slides on 2 days; August, 63 slides on 4 days; September, 21 slides on 2 days, (total 12 slides on 18 different days)." (180)

One of the earliest of these slides was the most famous of all, the Willey House Slide in Crawford Notch in 1826 in which the entire Willey family and two hired men died during a violent and torrential rain storm that hit the mountains August 27-28 that completely destroyed roads in Pinkham Notch, Littleton and Conway. The Saco River was reported to have risen 24 feet in 7 hours in Conway. The Ammonoosuc River rose 14 feet in the same period of time measured at Fabyan's. The second most famous slide is the Cherry Mountain slide that occurred on July 10, 1885, that trapped Donald Walker and who died of injuries 4 days later on what was to have been his wedding day. A month later, August 13, 1885 the impressive slide on North Tripyramid occurred. Flaccus' article has some impressive photographs from the AMC collection of some of these older slides. The weight of soil and rock transported downslope by all of these slides measures in thousands of tons.

Flaccus did extensive research on 29 of the slides he had identified (This was his doctoral thesis project for Duke University) noting similarities and differences. He identified three sections in each of the slides: the upper "slide section", the highest area of the slide where the soil is bared to bedrock; the "gully section. Where the slope begins to level out, the slide narrows to a gully form and cuts into the till which usually overlies bedrock at the lower altitude." (181); and the "stream scour section" where the channel is "severely washed and much broadened, all vegetation bordering the former stream bed has been removed, and the trunks of the trees bordering the scour are scarred and barked." The Gale River slide has all of these features just as described.

Flaccus measured slope characteristics of the 29 slides and averaged the degree of slope at the "slide section" at 32 degrees with a range of 25 to 35 degrees. He observed that slides are not likely on slopes of less than 25 degrees.

He plotted the altitudes for 270 slides and found that the clear majority of slides, 82 percent, had started above 3000' a.s.l. (182). Flaccus reported that their aspects, the compass direction they were facing, was not a significant factor. After degree of slope the most significant factors, are rainfall (although it's not clear how water is involved in triggering slides), the geology at the location of the slide including type of bedrock, and the "fluvial cycle" which involves the erosion and "aging" of landforms. Earthquakes were ruled out as triggering factors but interestingly some observers thought vegetation, moving violently in high winds associated with storm was responsible for triggering some slides including the South Tripyramid slide in 1889. Lightening along with loud thunder was said to have been responsible for the Cherry Mountain slide in 1885. Clearly the degree of slope and occurrence of torrential rains at the time of the slide are the primary factors but then the question remains about why they only occur in certain locations, why not in many of the locations that meet the criteria for slope, bedrock and altitude?

A brief burst of morning sunlight caught these birches and gave me a some hope that climbing to the summit of South Twin might be a good gamble.

Flaccus added a section on revegetation occurring on the landslides he studied and reported that on the slides upper sections where the bedrock is exposed vegetation will take a long time to recover and at high altitudes pioneer plants my be extremely slow growing. In the lower slide sections he found that the forest will reestablish itself in time and is most rapid on the flatter, deposit areas "which are heterogeneous mixtures of boulders, gravel, sand and organic matter (mostly macerated trees) deposited like moraines."(189). He suggests that slides less than 50 years old show mostly pioneer hardwoods such as the birches in the above photo into which the spruce and fir slowly dominating so that in 150-200 years the slide will not be noticeable to casual observers.

This is the small brook that drains the landslide and joins the Gale River just downstream from the slide site. Most of the rocks in the photo are granite. The brook is a conduit for nutrients leached out of the slide and transported downstream to other locales. The nutrients include both suspended and heavier particulate organic and inorganic matter, as well as cations and anions (ions) such as carbon, calcium, manganese, potassium, phosphate, etc. plus nitrates and sulfates to name just a few. Most of these come out of the soil, but they also come from the vegetation.

Looking across a shoulder of North Twin towards the summit of South Twin. I decided to try for South Twin on impulse and the warmth of the sunlight.

Looking back at North Twin from the Gale River Trail.

The third and last steep section of the Gale River Trail as it climbs out on Garfield Ridge.

Balsam seedlings along the exposed upper section of Garfield Ridge. There prolific numbers are a response to disturbances caused by high winds from the northwest that upend a lot of the firs from the north flank of Garfield all the way across the ridge and up the west flank of South Twin.

The snow helps one appreciate the sheer numbers of new seedlings huddled in these exposed sites that offer mutual shelter from the winds and help stabilize the soil in case of a blowdown.

Here is a site just below Galehhead Hut that has been disturbed countless times and struggles to achieve a tentative equilibrium on this exposed ridge.

A Christmas card from all the furry little creatures overwintering at Galehead.

South Twin socked in. The winds were light at the hut but the upper elevations were getting a little more and I decided to wait it out for a while before climbing higher. To the west there was some patches of blue sky. You reach decisive moments when you know if you go higher it won't change, but it you go back down it will clear up within 30 minutes.

Galehead Mountain was clear when I first go to the hut.

I sat around in the shelter of the hut for an hour until I began to really feel the cold

and the clouds began to descend again.

Looking down into the Pemi (Pemigewasset Wilderness) from the hut. I thought, with these clouds lifting a bit, I'd gamble a little more and started up South Twin only to have the clouds come down around me while a light snow began to fall at which point I bailed.

The shallow depth and firmness of the snow on the trail made it perfect for running so I was able to get my body temperature back up quickly.

and by the time I was down to the walkout part of the Gale River Trail, on the flats, it was clearing (as predicted) and still early in the day.......

.......but I continued down through these lovely colors.

Sunday, November 7, 2010

11-06-10 Mt. Jefferson: Felsenmeer & Glacial Geology

I finally, finally got North to the "Whites" again after what seemed like an eternity. On Saturday (11-06-10) I drove to the Cog Railway Base Station to meet Thom (pronounced Tom) Davis (P. Thompson Davis) a friend and Professor of Geology at Bentley University in Boston, MA. Our intention was to hike up Mt. Washington via the Ammy to tour the boulder fields, or felsenmeer, on the summit cone. Thom had generously offered me time from his busy schedule to explain current theories on how and when the boulder fields were formed. I was so excited to be in the mountains again I ended up being a bit early and while I waited for Thom I visited with the Ammonoosuc River for an hour. Even after the recent spate of rain the water level in the river had not risen dramatically.

Watching the Ammonsoosuc River churning through this gorge as it cuts a deeper and deeper channel through the bed rock is a reminder that water, in its myriad forms, is a key agent in sculpting the landscape as we see it today. Of course the sculpting has been going on for an unimaginable amount of time measured in millions of years, and it's not just water but the climate itself, the mix of moisture (as rain, snow, frost, and ice), temperature, and wind, that's responsible for the constant evolution of the landscape. What we see in the fractional moment is a mere snapshot, the blink of an eye, in terms of the continuum of change that's occurring around us however slowly.

Thom has been around the White Mountains as long as I have and has been at the fore front of local alpine and glacial geology for many of those years. As a college professor he's authored numerous papers and taken a lead in several ongoing discussions that, at times, become controversial, dealing with the complex nature of the geology and glaciology of the White Mountains. Thom speaks of these discussions as being friendly and collegial. One that he's been involved in for decades focuses on whether alpine glaciers occupied the glacial cirques in the Presidential Range after the Wisconsinan Glacial period. The accepted theory is that alpine glaciers predated the continental ice sheet. Thom's magnum opus is his extensive research of Mt. Katadin in Maine but the White Mountains occupy a lot of his time. He'll be working with geologist Brian Fowler on a new Map of The Surficial Geology of the Presidential Range that Brian collected a trove of data for this past summer. The mapping project is in collaboration with J. Dykstra Eusden, of Bates College, who recently published The Presidential Range: It's Geologic History and Plate Tectonics (2010) with its excellent fold-out map of the bedrock geology of the Presidential Range. The two maps, the surficial geology and the bedrock geology, will compliment each other.

(These new maps update R.P. Goldthwait's Geology of the Presidential Range (1940) and the Geology of the Mt. Washington Quadrangle published by M. P. Billings, et. al. (1946). Also in 1946, Billings and his cohorts collaborated with R.P Goldthwait on a booklet titled Geology of the Mt. Washington Quadrangle published by the New Hampshire Planning and Develolpment Commission. In 1951 Billing's published Geology of New Hampshire reprinted in 1962, 1968, and 1980, that was a companion to R.P. Goldthwait's 1951 publication: Surficial Geology of New Hampshire. A third companion volume published in 1951 covered the minerals of New Hampshire.)

On our hike Saturday I found that Thom possesses an encyclopedic knowledge of local geology and it was a great pleasure and educational experience to hike with him. Since we had a late start and the day was a bit dark with a thick mist settled low over the mountains on Thom's suggestion we decided to hike up Caps Ridge Trail to the summit of Jefferson to find some felsenmeer to poke around in instead of hiking up Mt. Washington.

This is Mt. Jefferson (5716') (in a photo from 8-29-10)(note the felsenmeer in the foreground). Caps Ridge Trail perches on that smooth incline slanting down on the right from the summit. The trail begins at 3,011 feet right off the Jefferson Notch Road (closed from mid-November until mid-May). This relatively high starting elevation shortens the hiking time up to the ridge. It's a rugged trail in places, offering some challenges particularly with winter conditions.

The smooth-looking incline of Caps Ridge in the photo shows the direction of the "continental" glacier, the "Wisconsinan", as it ground its way over and around the Presidential Ridge. The vast ice sheet traveled right to left in the photo, or northwest to southeast. The Great Gulf Wilderness is on the left in the photo, in the shadows.

A lovely, light snow was falling as we left the started up Caps Ridge. The trailhead is a little higher than the Base Station thus a small change in the weather. From the trailhead up to about 4,300 feet the Caps Ridge Trail crosses granite bedrock called "two mica granite", an igneous rock classified as "a light gray to white granite" found in several areas in the Mt.Washington quadrangle including a large area north of Pinkham Notch.

As we climbed Thom reminded me that felsenmeer occurs in all types of rock including granite, sandstone (in the Canadian Rockies), volcanic (the Olympic Mountains) and in metamorphic schists as in the Littleton Formation of the Presidential Range in the White Mountains. Different rock types react differently to the physical and chemical processes involved in the formation of felsenmeer but the key ingredient is climate. The climate responsible for the formation of the felsenmeer includes lots of water and daily (diurnal) or seasonal temperature fluctuations that cycle between freezing and thawing over relatively short periods of time. Since I kept referring to the ancient past in reference to the felsenmeer, Thom reminded me that iit's still going on today.

The forest between the Jefferson Notch Road and treeline on the Caps Ridge Trail shows the impact of perennial disturbances. The ridge portrudes northwesterly from the main ridge of the Presidential Range and is like a ships prow that's subjected to a continuum of intense storm activity and high winds. It also creates a venturi-like effect that increases air density and, with it, the speed of air masses climbing up over Mts. Jefferson and Clay.

In the freeze-thaw cycle, as the water melts and expands, it can exert a force of 22,000 pounds per square inch and in a paper on felsenmeer Thom that cited it stated a force that great easily fractures granite.

Frost plays a pivotal role in the formation of felsenmeer: first by prying apart (fracturing) jointed bedrock into rough blocks (boulders) and stones and, second, by heaving the blocks upwards from the bedrock several feet (1-2 meters) until they rest on the surface or on top of each other where they are evident today in the vast boulder fields called "felsenmeer" (German for "sea of rocks") on the higher summits and plateaus of the Presidential Range.

The mist and falling snow persisted as we climbed above treeline and across the first of several "Caps" which are massive protrusions of bed rock. The trail goes up straight over each of the caps which provides some novice rock climbing in a few places and some fine views of the ranges.

This massive "chunk" of mica schist, a member of the "Littleton Formation", looks intimidating in the mist and snow. In my youth, presented with this in my path, I would have eagerly climbed the rock, rather than hiking around it, pretending I was on a first winter ascent of the Eiger.

Initially the Littleton Formation consisted of thick sediments deposited on the floor of an ancient ocean where they were transformed into sedimentary rocks. Much later they were transformed into metamorphic rocks, in this case mica schists, under enormous pressure and heat, the result of continents, tectonic plates, shifting and colliding. The current theory holds that the White Mountains were formed during the Acadian Orogeny during the mid-Devonian epoch more than 400 million years ago. Eusden, using a computer model, determined that at the conclusion of the Acadian mountain building period the White Mountains were as high in altitude as the present day Rockies; around 15,000 feet (6 km) above sea level.

This large block of the Littleton mica schist is serving as a trail marker (the rectangle of yellow paint). Thom pointed out that the cracks are visible traces of the folding that occurred in the rock before it cooled. He added that the schist was "deformed" several times over the last 400 million years, the last time roughly 200 million years ago.

He also pointed out these stones sheltered under the block of schist a number of which are "glacial erratics".

After crossing over the last Cap, at about 4,500' we entered a large boulder "field". This is the felsenmeer and both the sizes and shapes of the rocks vary enormously. How the boulders get stacked and lie on top of each other, even huge blocks like the one in the foreground, is the feature of the felsenmeer that's captured my curiosity.

If you enlarge this photo on your computer you can see soil around the base of these boulders which is likely a relatively new soil consisting of "fines" (small particles) and pebbles created by the continual erosion of the larger boulders by "frost weathering".

At this point, the formation of the felsenmeer has been explained in rather simple terms, but, as Thom observed, it's a much more complex process involving interactions between the types of bedrock, the degree of slope, temperature gradients, available water, soil development, and the specialized environment in which this all takes place. I'll try to help you navigate through the beauty of these complex processes starting in a minute, but first there's some terminology that needs defining.

The mist was beginning to thin as we approached 5,000' and there was as blue tint in the sky behind Thom and there was a the feeling it was about to clear.

Two terms directly related to the felsenmeer include: "Quarternary" and "Periglacial". The Quarternary Period is a unit of geologic time comprising the last 2.6 million years. It is often referred to as the Quarternary Ice Age. It began with the beginning of the Pleistocene and the beginning of a cold, dry climate that produced the glaciation of the northern hemisphere. The Quarternary also covers the time that human civilization began to emerge. To refresh your memory the Quarternary is the present time period of the Holocene Epoch of the Cenozoic Era. The Holocene bring us to the present "interglacial period".

A minute or two later, with a little fanfare, the clouds rolled away to the south opening up vistas that continued to widen as we climbed.

"Periglacial" in one usage describes geomorhpic processes (e.g. the felsenmeer) occuring on the periphery or edges of glaciers and glacial areas. My attempt at a definition of Periglacial is as follows: An area not (necessarily) buried by glacial ice but subject to intense freeze-thaw cycles and that may have geomorphic processes occurring as the result of permafrost. On-line dictionaries and encylcopedias have more definitions that may, or may not, be useful.

Periglacial Processes and Environments (1973) by A. L. Washburn (Albert Lincoln Washburn and referred to simply as "Link") is considered the standard reference in the field today for studying periglacial processes. With Thom's help I was able to obtain a copy of Washburn's book from a small shop in Cornwall, UK. (The postage was more than the book price.) For the past few weeks I've been reading Washburn and a other papers on periglacial phenomenon from around the world that Thom forwarded to me and I've been enjoying this leap into an astonishing new world. I've discovered that my curiosity with felsenmeer is well deserved and that many of the questions I've had regarding its formation are shared by many others.

The clouds continued to peel away exposing the summit of Mt. Washington and a bit of Mt. Clay.

In his book, Washburn reports that the term Periglacial "was introduced by Lozinski (1909) to designate the climate and the climatically controlled features adjacent to the Pleistocene Ice Sheets (the large glaciers covering most of the northern hemisphere).
"It's been extended to designate nonglacial processes and features of cold climates regardless of age andof any proximity to glaciers. As a result there have been varying usages. Although not without criticism because of its lack of precision, the term is being widely used in the extended sense, as herre, because of its comprehensiveness.

The term has not generally recognized quantitative parameters, although some rough estimate of precipitation and temperature limits have been given. According to Peletier's (1950) estimate the periglacial morphogenetic region is characterized b an average annual temperature ranging from 5 degrees (F) to 30 degrees (F) (-15 C to -1(C)). Peletier quanitified annual rainfall (excluding snow) ranging from 5 inches to 55 inches (127 mm to 1397 mm). The diagnostic criterion is a climate characterized by significant frost action and snow-free ground for part of the year." (Washburn, pg. 1)
Frost action described by Washburn includes "Frost Wedging": "the prying apart of materials, commonly rock, by expansion of water upon freezing. It's synonymous with frost splitting and congelifraction. Frost wedging characteristically produces angular fragments that can be of widely varying sizes, ranging from huge, house-size blocks to fine particles" (58), as in the photo above and several others presented here. This felsenmeer is part of an extensive area beginning at 5,000 feet and that wraps around the Jefferson summit. Whether there is a distinct lower edge, or boundary, for the felsenmeer is often talked about by researchers. In the White Mountains the felsenmeer, generally, is confined to above 5,000 feet but that may be because of the slope which steepens below that altitude in many places.

Washburn writes at length about the subtle details regarding rock material, the environments, the climate including zonal climate, local climate and micro climate, time, and topography, etc. He writes of the interrelationship between these factors as "in periglacial environments, thawing of snow or ice adjacent to dark rocks warmed by insolation (the sun) is common at subfreezing air temperatures and must be a potent factor in frost wedging when meltwater seeps into joints and refreezes." (58). In another observation he says "The frequency of freeze thaw cycles is an important control in the effectiveness of various kinds of frost action, including forest wedging. However, the purely climatic factor of the number of times the air temperature passes through the freezing point is not, in itself, an adequate measure of the effectiveness. The insulating effect of snow and vegetation, the nature of the rock material, and the rapid attenuation of temperature fluctuations with depth must all be taken into account in evaluating the fequency and effectiveness of freeze-thaw cycles in rock materials." (58)

Well above treeline the trail takes the aspiring hiker over several false summits that, from above, looks like this. The desire to go higher for us was the desire to get above those clouds in the background and bask in the sun for a bit.

From studies in the Narvik Mountains of Norway, The Drakensberg Plateau of South Africa that Thom sent be papers on as well as Washburn's work in northern Greenland and arctic Canada, and Goldthwait's work in the White Mountains there's a lot of information about felsenmeer we can rely on. Here's a short list of things we definitely know: felsenmeers have an average depth of 39 inches (1 meter) although they're reported, in some studies, to be 70 inches (2 meters) in depth. They're found in high mountain periglacial environments (such as the area above 5,000 feet a.s.l. in New Hampshire's White Mountains) near or above the Arctic Circle, in Iceland, and other areas mentioned above. They are common in these regions, e.g felsenmeer is not unique to the White Mountains and Ragnar Dahl's prolific studies (1956-1966) of felsenmeer in the Narvik-Skjomen area of Norway indicates extreme similarities in the felsenmeer he studied and the felsenmeer found in the northern Presidential Peaks (Mts. Washington, Clay, Jefferson, Adams, Sam Adams, and Madison) of the White Mountains.

We also know that felsenmeers form on slopes of 25 degrees or less. (I'm accepting this until there's an opportunity to accurately measure degree of slope on the east side of the Mt. Washington summit cone.) A higher degree of slope results in the boulders being transported by gravity downslope. The existence of the felsenmeer and the processes involved in their formation all fall into the category of "mass wasting", and, one of my big questions, the age of the felsenmeer, is accepted by most researchers as relatively young. Most of those studies state that felsenmeers formed since the end of the last ice age 14,000 to 20,000 years ago.

Thom and others have tried dating the felsenmeer using cosmogenic derived data based on the exposure of the rocks to cosmic rays. That data has contained some flaws that make it difficult to form conclusions. At any rate, the question of precise age of the felsenmeer is still open although the figures presented seem reasonable and comparisons with other periglacial environments these processes might still active and on-going. Daily and monthly temperature gradients and mean temperatures for each of the 12 months of the year are available through the Mt. Washington Weather Observatory and indicate the potential for the occurence of periglacial processes during several months of the year including spring and fall. In Norway the micro climates in and around rocks and the amount of available moisture necessary for freeze-thaw cycles to occur were studied carefully over several years. The findings in those studies would most likely have a close "fit" to conditions here, in the White Mountains.

Questions that come up, at least for me, involve the position of some glacial erratics in the felsenmeer like the sub-angular boulder in the center of the photo that Thom pointed out just literally a few feet below the summit of Jefferson and...

this one located right at the summit. We assume that felsenmeer formed following glaciation and was not part of the glacial process so the presence of erratics in the boulder fields poses several questions regarding their transport there. R. Dahl (1966) quotes studies in which erratics were found in block fields that are "allochthonous" meaning from out of that area and possibly derived from glacial till deposited there. Other studies cited by Dahl considered the felsenmeer to be both "autochthonous" meaning locally derived and allochthonous. One report stated that, "it is not uncommon to find many erratics which are not frost-weathered in the block-field zone. If they are numerous, it is possible that the block field consists of glacial till." (R. Dahl, 58)

Looking at this photo of Jefferson's summit brings up one a nagging questions about the felsenmeer and how these large blocks got piled up on top of each other in this random assortment. An answer is provided by Washburn and his explanation of two more terms from the periglacial lexicon: Frost heaving and Frost Thrusting.

"Pressure generated by freezing water is exerted in all directions," Washburn wrote, "but they are expressed in soil movements only upwards and horizontally. The vertical expression is called heave and the horizontal, thrust.

"Blocks, frost wedged from bedrock, along joints, are raised (heaved) well above the general surface in places although the blocks are still tightly held by the surrounding bedrock." he added.
Photos in Periglacial Processes and Environments show huge blocks that have been heaved upwards and that are resting on other blocks in the same manner as evidenced on the summits of Mt. Monroe, Mt. Adams, and on Mt. Jefferson, where the summits themselves consist of felsenmeer. The obvious conclusion is that, as the felsenmeer is not of great depth and the bedrock is only a few feet below the random assortment of blocks, the individual blocks were frost heaved upwards in the manner described and at somewhat different times.

Another term, "upfreezing", describes the mechanical action of frost on pushing stones upwards to the surface. In 1973, at the time Washburn's book was published, "the mechanics of upfreezing is poorly known," the author wrote. He experimented with variations of this process by placing "targets"(e.g. wooden dowels) in the ground at varied depths and measured elapsed times for them to be pushed out of the ground. He and other researchers then developed what were called the "Frost-Push" hypothesis and the "Frost-Pull" hypothesis" both of which are variations of frost heaving but have importance in the periglacial process called "Patterned Ground" which is a well known phenomenon in the alpine areas of Mt. Washington.

The clouds seemed to settle down into the cooler area of the valley but then began to yo-yo around us and a higher level of clouds filtered the afternoon light making it cooler and making it feel later than it was. Odd pieces of Mt. Washington are showing through rents in the clouds to the extreme left.

Another question I have about the formation of the felsenmeer within the time line we have discussed is whether the boulder fields began to form after the culmination of the ice sheet and as it began melting back leaving the summits clear of ice little by little down to about 5,000 feet a.s.l. as in the photo above if you imagine that the clouds are the top of the ice sheet.

The reason for asking is that it might explain several things. One is that the melting ice would have provided the ample water needed for frost wedging of the bedrock as well as the ambient temperatures close to those proscribed by Washburn and others as optimal for periglacial processes including frost wedging/weathering to occur.

Thom's response to my questions about timing and time lines is that almost all of the periglacial processes we've been exploring occurred concomitantly (in the same time period) as the ice sheet dissolved.

In this zone on the south slope of the Mt. Jefferson 300 feet below the summit the slope eases and we find soil that has collected here from the mass wasting of materials from the boulder fields higher up on the mountain. The soil is periglacial in origin and in its more primitive state would have been mostly fines and gravels from the frost weathering process but once vegetation is supported an O horizon develops as in the photo.

This photo shows the bedrock to the right and gelifluction (a form of "mass wasting") occurring in the movement of the soil, to the left in the photo, down slope. Terms for mass wasting described by Washburn include avalanche, slushflow, slumping, frost creep, rock glaciers, and gelifluction. Gelifluction, similar to solifluction, is the slow downward flowing of waste saturated with water over frozen ground. Solifluction is the same process but not restricted to cold climates or frozen ground. Washburn states that "Gelifluction is unequivocally periglacial." (173). His insightful research into frost heaving and mass wasting opened up a window on myriad kinds of vertical movements caused by frost action but also lateral movements and combination of the vertical and lateral movements such as "mass displacement" and "frost cracking".

Mass wasting may have been the origin of the larger, nearly level areas of vegetation on the Presidential ridge, what are referred to as "lawns'. These lawns on the Presidential Range were referred to by Goldthwait and others as remnants of the New England Peneplain, an ancient erosional surface left over from pre-glacial epochs. The lawn in this photo is a segment of what is descriptively called Monticello Lawn as it's located on Mt. Jefferson. Monticello Lawn consists of many acres and curves around the southeast side of the Mt. Jefferson summit cone at around 5,000' a.s.l. Parts of Monticello Lawn contain "hummocks" and "steps" which are features of periglacial environments and the lawns, themselves, are likely the result of periglacial processes such as mass wasting as mentioned above, as are smaller grassy areas (smaller lawns), referred to by Goldthwait as "grass cells" that are conspicuous in the area above treeline. I've often thought about doing a research project focusing on these "cells" to better understand their origin, micro climate, expansion and/or contraction, and their ecological significance.

A last thought about Monticello Lawn is a memory of a distant summer when some overly ambitious (exhuberant?) hut croo set up a croquet game complete with stakes and wickets, colorful croquet balls and a couple of mallets leaning on a well anchored lawn chair on which a Sunday edition of the New York Times was also anchored (from the wind) to look like someone had been playing a game of croquet and just left--all for the amusement of passing hikers.

This Bigelow sedge shows the raking force of the wind as it moves from the northwest around the summit and across the lawn. I've been here on winter trips when the only way across was to crawl because the wind was so violent. Washburn makes several observations about the contribution wind makes to the periglacial environment including the creation of dunes and sculpted rocks called ventifacts. The intensity of the wind that blasts the Presidential Range is world famous and impacts the periglacial environment by inhibiting vegetation growth above 5,000' a.s.l. and it may sculpt rocks and landforms as well.

Looking back up to Jefferson's summit as we begin descending back down into the clouds.

Washburn's explorations of vertical and horizontal frost action in periglacial environments has increased understanding of other periglacial processes like "frost sorting" which produces small and large stone stripes, stone polygons and large and small stone circles that are found on nearly level ground or on slopes of 3 degrees or less like the lawns around Mt. Jefferson, and Bigelow Lawn. If Thom and I had been carrying a tall step ladder we could have taken a photo from the top of it looking straight down on these rocks in the foreground to show they've been frost-sorted to into large stone polygons with Bigelow sedge in the cell-like centers.

In the past year we looked at block nets and block lobes (on Mt. J. Q. Adams), block streams and what might be a rock glacier on the Kings Ravine headwall all of which are associated with the periglacial processes of "creep". We've also looked at sorted and unsorted stone stripes and stone polygons on Bigelow Lawn on Mt. Washington's east side just north of the junction of the Davis Path and Camel Trail that rival those photographed by Washburn in Greenland and Arctic Canada.

Time to head down.

Winter's approaching.

This is the western edge of the lawn. To the left the slope drops steeply towards the valley. The gentle slope of the lawn is important as it defines the limits of vegetation here as well. From here we descended back down into the mist and light snow that was still falling. It was unique to hike down the mountain and into a snowstorm.