Saturday, November 14, 2009

11-14-09 Large blocks on JQ Adams have sharp edges

These blocks are on the summit (of JQ). They have relatively sharp, clean edges but, again, there is nothing to suggest that any of the fracturing of the schist is current. The shapes and sizes are irregular as are the shapes and sizes of the blocks that generally make up the felsenmeer and they're encrusted with lichen.

With the intention of completing this discussion about the felsenmeer I want to reinsert the timetable projected by Richard Goldthwait (from The Geology of New Hampshire, 1951) and what he felt is a realistic chronology for the arrival of the last Wisconsian ice sheet and it's ablatement:

180,000 years ago and again more than 50,000 years ago, short mountain glaciers slowly scoured out the deep cirques and valley of the higher White Mountains;

Between 40,000 and 60,000 years ago a great ice sheet gathered in northeast Quebec and grew southward overwhelming mountain glaciers in New Hampshire;

More than 20,000 years ago this ice sheet began to melt and waste away (ablate);

Less than 14,000 years ago the last significant ice mass seems to have completely diappeared from New Hampshire.

This timeline was developed by three generations of Goldthwaits in collaboration with Ernst Antevs, Marvin Billings and Katherine Fowler-Billings, Randolph and Carleton Chapman, D.W Johnson, Armin Loebeck, and many others. It evolved from the best scientific practice during a period stretching more than 50 years up to the early 1960s. The timeline and conclusions drawn by this formidable group of geologists relative to the glacial history of the White Mountains have been challenged by a few scientist, most notably Will F. Thompson, a physical geographer, in 1960, but the challengers didn't produce an alternative chronology so I feel that the timeline developed by Goldthwait, et. al.,is accurate for it's time (the 1960s). It's only a matter of time before we have more accurate measurements some of which are becoming available as I write. In a personal conversation on 11-07-09 with Thom Davis of Bentley College (Boston), a geologist, he observed that cosmogenic measurements taken during the past few years focusing on the age of the felsenmeer on the summit of Mt. Washington point to the accuracy of 14,000 years as the time the continental ice sheet had fully ablated, but he said that there are variations, too, and that they were working out some of the bugs in their measurements. This underscores the difficulty in obtaining an accurate number even with the superior technology. I personally trust the number of 14000 years BP to designate the time that the last Wisconsian ice sheet had completely melted back from the White Mountains.

The smaller block on the left has an unusually sharp, straight edge.

The image, then, of the continental ice sheet between say 18,000 to 14,000 years ago is important in the discussion of the felsenmeer. I've had to correct my perspective several times as I've read through all the literature. In The Geology of New Hampshire (1951) Richard Goldthwait created a reasonably accurate picture of what the ice was doing and what it looked like during those 4000 years that it was melting and evaporating free of the White Mountains. The correct image is of the ice shrinking in place. It did not recede or retreat back to Canada (one image I had). It merely stopped, or, perhaps, slowed down, and melted in place. There were probably times, a thousand years, when it advanced a bit, but like the Greenland ice cap today, it was hemorrhaging most of those years. It was melting from the bottom up and from the surface down while billions and billions of gallons of water poured off the ice in turbulent cascade to form huge lakes and rivers as it rushed to the ocean.

In closeup the block is weathered on both sides but still looks straight enough to have been cut by a saw.

The melting caused the glacier to thin and as it did the high peaks of the White Mountains emerged as islands. Goldthwait wrote, "The highest peaks-Mt. Washington and Mt. Adams-protruded through the ice first as it grew thin and looked much as they do today when they rise above a sea of clouds." (1940, pg. 28)

For thousands of years, then, the higher peaks were Nunataks (from the Inuit: Nunataq), islands protruding above the ice with their summits exposed to the elements while their flanks and the valleys between them were still encased in glacial ice.

Mt. Madison from J.Q. Adams. The light changed briefly when a high layer of clouds moved across the range creating a sensation it was late afternoon. Note that the entire south face of Mt. Madison is free of rime and snow as it's sheltered from the more intense and frigid winds that come out of the north and it faces the sun directly so, generally, it's warmer niche. Mt. Madison's south face, the southeast face of Mt. Adams and east face of Mt. Jefferson usually have deep snow packs in the later winter months due to the prevailing wind coming out of the north and blowing snow from the west side of the range over the ridge where it settles on the leeward slopes of all the Presidential peaks and collects in great depth in the cirques of Great Gulf, Gulf of Slides, and Huntington and Tuckerman Ravines.

Looking at Mt. Madison with this dusting of snow it's possible to see where the bedrock protrudes along the ridge to the very summit and the felsenmeer appears to have fractured from that spine and fallen down both sides of the mountain from the ridge.

If you picture Mt. Madison with a vast sea of ice coming to within a few feet of the summit and you could sit on J.Q. Adams for a thousand years while the ice melted you might have the illusion that it's the summit that's rising when it is actually the ice surface that's decreasing in altitude and exposing more and more of the land mass. Imagine being able to run from the summit of "J.Q." straight across to the summit of Madison, or Carter Dome, on the ice! Think how easy it would be to do the '4,000 footers', just wait until the ice melted down to 3,999 feet and then do them all in a couple of days on skis. No more sweaty, tiresome hiking up mountain after mountain wondering what possessed you to do something so pointless!

Here's a dizzying view down the south face of "J.Q." into the U-shcaped cup, or cirque, of Madison Gulf. According to Goldthwait this U-shape was "carved" by one of the nine small, local, or alpine, glacier that formed on the south, east, and northern flanks of the Presidentials. He reported that, "Madison glacier was short and did not flow far enough down the slopes to join the Great Gulf system." (1940, pg 13.) The Great Gulf 'system' consisted of an 8 mile-long glacier extending from the 'schrund' halfway up the Great Gulf headwall all the way down the valley visible in the above photo. It incorporated two smaller glaciers formed on Mt. Clay and Mt. Jefferson. Looking down the face of Mt. Adams there is more evidence of mass wasting with scree-like boulder fields towards the south. The Star Lake Trail that I used when I climbed Mt. Adams back in July traverses this slope several hundred feet down.

The southeast face of Mt. Adams is a broad, slightly concave slope more than a thousand feet long. Enormous amounts of snow accumulate on this face and lingers well into the late spring. Once the snow settles, usually by mid-March, the snowfields on Madison, Adams and Jefferson provide excellent skiing. I've found that this slope and the east face of Mt. Jefferson extending all the way down to the floor of Jefferson Ravine have some of the best skiing in the Presidentials.

Goldthwait observed that the continental ice sheet melted faster on the south and east sides of the White Mountains, again due to a generally warmer macro/micro-climate, which might be a significant factor in the low concentration of felsenmeer on the east-facing flanks of the Presidentials (again, not completely as on Mt. Washington's east slope).

This is the upper most view of the east slope of J. Q. to just below the summit of Mt. Adams and no there's felsenmeer . There's a lot of vegetation as noted back in July with balsam 'krummholz' growing to within 18 feet of the summit of Adams. Several indicators provided by the high elevation of the krummholz are: it's warmer on this slope then other slopes of Adams, there is moisture readily available, and there's soil. As Kate, one reader pointed out, frost hardiness is one of the primary limiting factors, or stressor, and, along with the wind effects the formation of 'timberline'. Frost hardiness is an adaptation by plants to temperatures that normally kill most living tissue. In perennial plants with high levels of frost hardiness, like balsam fir, dwarf (or alpine) birch, black spruce, the sugars in the plant cells are converted to starches when the length of night increases and the ambient temperature decreases substantially. The starches become colloids in the cell vacuoles and overwintering proceeds. This is a continuous process throughout the winter as these plants photosynthesize whenever there's available sunlight.

Looking over at the summit of Mt. Adams from J. Q. Adams. Note the large outcropping in the center of this photo which is the eroded top of an upwardly arching fold of bed rock that may be Tourmaline or another mineral that was forced upwards hundreds of millions of years ago between the beds of Littleton Schist. I have to admit I haven't noticed this outcropping before or explored it but I'll put it on my list of things to see and do on Mt. Adams in the near future.

Another limiting factor in the way 'timberline' evolves is soil. As Monihan and others have pointed out the plants making up the highest communities in the White Mountains, mainly black spruce, alpine birch and balsam fir, reproduce by "layering". Black spruce and balsam fir rarely produce seed cones above 4800-5000 feet. Layering is the predominant form of propogation and utilizing root-forming (meristematic, or root apical meristematic) tissue in the plants' lower branches, those closest to the available soil, and eventually these branches grow as separate plants. Since reproduction is absolutely necessary for these alpine plants that depend so much on each other in creating a niche the soil itself becomes a limiting factor.

It was so warm out of the wind on top of "J.Q." that I wanted to take a nap there in just my T shirt. I headed back to the col between J.Q and Mt. Adams descending across a gently sloping sedge lawn to regain the Airline Trail. The lawn was surrounded by blocks of schist in random sizes that were, in some places, clumped tightly together, and in other areas, spread out like rocks on a New England pasture. The col itself is a level, diamond shaped lawn surrounded by blocks of schist.

This is a map drawn by Richard Goldthwait (with the assistance of many graduate student interns) in 1937 of the area I was standing in when I took the above photo. It shows a "horseshoe-shaped lobe" of felsenmeer, large and small blocks, that have moved down the steeper incline from the summit of J. Q. Adams into the col between J. Q. and Mt. Adams. The manner in which the blocks appear to have "flowed" downhill from the bedrock above and then been pushed outwards, away from the "lawn" they surround, by the freezing and thawing of the soil cells over an immense amount of time contributed to Goldthwait's concept of how the blocks of schist moved, what he termed "creep".

A glimpse back over at the summit of J. Q. and the area identified in the above map from the Air Line Trail. On the map you can see the Air Line Trail where it cuts across the lawn/soil cell near the bottom of the horseshoe-shaped lobe. In the photo you can just make out two hikers, one wearing a red parka, who are near the edge of the lobe.

Goldthwait (1940) wrote of the felsenmeer: "The blocks form a distinct blanket over till (soil left by the melting glacier) as on the summit of Mt. Washington. Where not to numerous the blocks are arranged in a pattern simulating nets or stripes or horseshoe-shaped lobes and enclosing areas of open fine soil matted with grass. These soil cells are common on Boott Spur, Bigelow Lawn, and parts of each peak above 5000 feet altitude. Steeper slopes like those on the west and northwest sides of Mt. Washington, Mt. Jefferson, and Mt. Adams have horseshoe-shaped banks of blocks 20 to 60 feet long and 15 to 50 feet broad. Each lobe encloses a high grassy center inclined at 10 degrees to 20 degrees (16 degree average).

"Two kinds of motion are evident in such soil cells. The stretching of the block nets into block stripes on slopes which increase downwards from 3 degrees to 5 degrees and viscous shape of the block lobes clearly showdownhill creep of masses of soil by soliluction. The segregation of the big blocks into nets, stripes, and walls leaving open grassy coneters ia distinct but little understood sorting process. This sorting does not involve a deep circulation of blocks upward from within the soil because several excavations have revealed the very shallow nature of these forms. The blocks did not move far up out of the till in any sort of up-freezing process. However, the sorting does involve an actual expansion and outward push from each soil center or soil stripe towards the blocks because the blocks tend to be pushed together like dominoes on edge. This is undoubtably due to the fact that the fine soil retains more water than the loose blocks. When this freezes and expands it exerts a horizontal push on the blocks" ((Goldthwait, 1940; pgs 35-37).

Once out of the col and back on the Airline Trail on the final bit up to the summit of Adams the landscape changes to one dominated by felsenmeer, the "distinct blanket of blocks". There are no soil cells matted with grass or horseshoe-shaped lobes on this part of the mountain.

The felsenmeer actually begins lower on the mountain than the col between JQ and Adams. The felsenmeer begins a little above the Gulfside Trail where the trail traverses a level plateau above the lip of Kings Ravine. The felsenmeer extends northwestward almost to the col between Adams and Sam Adams near Thunderstorm Junction. The eastern boundary runs parallel to the Airline Trail up to the summit of Adams and includes some of the north and west sides of J. Q. Adams. The felsenmeer appears to wrap around the summit of Mt. Adams like a cloak.

The felsenmeer on Adams, in other words, covers an extensive area and when you look across this "sea of rocks" the sheer mass of all the rock is impressive. There's an enormous amount of "loose" blocks of schist covering hundred and hundreds of acres and it's impossible not to wonder where they all came from, when, and why they so uniformly cover parts of the mountain.

"Following glaciation the most marked changes affecting the Presidential Range have been surface changes wroiught in a period of intense frost," Goldthwait wrote. "All of the ledges above 5300 feet on Boott Spur, Mt. Washington, Mt. Jefferson and Mt. Adams are riddled with cracks and half detached blocks. Many of these may have been glacially smoothed as the ice sheet uncovered the peaks. However, freezing water had wedged open the cracks little by little and detached most of the smoothed surfaces. Several centuries of such quarrying has littered the mountain tops with a veneer of angular rough blocks."(1940; pg 30)

This photo is from just below and looking up at the summit of Adams. Goldthwait suggests that the blocks are like pieces of a massive puzzle that have toppled a short distance from a parent ledge. "More often an angular block will be found to fit exactly onto a rough ledge directly up the slope, or, groups of pieces just below the ledges which have quartz veins will show fragments of the same veins. the ragged angularity of the blocks also suggests that most of them were moved by post-glacial creep rather than by the moving glacier." (1940; pg 30)

After reaching the top of Adams I descended again in a straight line down the north side. This photo is looking back up towards the summit of Adams. The random, jumbled formation of the blocks is striking as is their varied shapes and sizes. There is distinct weathering of the rock evidenced by the rounded edges of many of the blocks.

This is a view across the north side of Adams a few hundred feet below the summit and shows a relatively gentle slope, a pocket, blanketed by the blocks. There are no lawn fragments of soil cells in this vast area.

Goldthwait, in his 1939 paper, asks: "When was the frost so active? One can only speculate how long features like upended long blocks might remain in place and how long patterns of blocks might remain in place and how long blocks might retain their definity. The best guess is that the preservation of soil cells has not lasted longer than the 10,000 years and more since last remnants of the ice sheet lingered in northeast Quebec. It should be noted also, that all side of the blocks have been pitted by the chemical action which lichens promote and etched by the driving snow and frost. For a long time these blocks were toppled and turned end over end to become uniformly etched." (Goldthwait, 1940; pg. 30)

Ernest Antev, a colleague of James Goldthwait, Richard Goldthwait's father, referred to the felsenmeer as "archaic" and "prehistoric".

In a summary written for the 1951 publication of "The Geology of New Hampshire, Part I Surficial Geology" Goldthwait writes: "During the uncovering of summits of the White Mountains by the melting ice sheet, intense frost action split ledges into angular blocks, moved them about, and redistributed the till and boulders. Millions of these frost-cracked blocks make the cone of Mt. Washington look like a great rock pile even though solid ledge lies only a few feet down. For a considerable time while only the very surface of the mountain was thawing and being loosened from the frozen ground under it, all the high-level blocks and juicy dirt masses were slowly moving downhill.

"The most striking result of this prehistoric frost action is the gathering of rough stones into belts which form patterns like a net over the flatter surfaces. Apparently the stones and blocks were forced outward from dirt centers. Upon freezing, the whole soil mass expands outward from the clay-rich centers which hold more water, and as it thaws, some of the fines (smallest soil particles) seem to fill spaces occurpied formerly by rocks thus crwding them outward. As adjacent soggy soil centers expand reatedl, stone and blocks from opposite directions are squeezed together to form boulder-filled troughs. The slabby pieces are pushed together so tightly that many stand up on end like tombstones." (Goldthwait 1951, pgs 51-52)

In a 1968 paper presented at Dartmouth College Goldthwait made minor changes to this nut-shell description of the post glacial geology of the Presidential Range. The thrust of that paper was to respond to the question of whether the small local alpine glaciers returned to the northern Presidential peaks in the period of time following the melting of the ice sheet.

This "lawn" or soil cell is close to the Gulfside Trail four hundred feet below the summit of Adams. Note the steepness of the slope covered by felsenmeer in the immedate distance.

"These large soil cells or groups of blocks are not moving today. To make sure of this, two hundred blocks, in all sort of position were painted and accurately located by measurements with steel tape from solid ledges. After a year these were remeasured and none of them had moved beond the small limit of error of the measurements. Even long pointed blocks tipped on end and small blocks balanced on top of larger ones stayed in place." (Goldthwait, 1940; pg. 30)

"Furthermore the green and gray lichens which cover all these rough schist blocks take many years to grow and yet virtually all of the blocks on these high peaks rest lichen-side up. No fresh split rock surfaces appear on the ledges." (Goldthwait, 1940; pg. 30)

Snow settles in the joints between the blocks of felsenmeer sublimating into ice through compaction during the winter months. There has been controversy on the role of the ice in the interstices of the felsenmeer and whether it provides the necessary moisture to move the blocks in normal seasonal freezing and thawing cycles. If the blocks were moving, even infinitesimal distances, as a result of the routine seasonal freezing and thawing of the moisture between the blocks there would probably be some evidence of the motion today. As Goldthwait points out, other than the mechanics of the moisture-frost-expansion hydraulics that far back in a prehistoric time pushed rocks aside into discernible patterns, there is no evidence to promote this theory that the felsenmeer is is constant motion.

A balsam fir encased in a blanket of snow where it will harbor for the winter. This is probably one of the key survival strategies of plants in the alpine zone, not just to stay low, but to trap snow that forms a protective blanket and that also holds tight to moisture for later use.

The sedge, mosses, tufts of diapensia and other plants have similar strategies. They "hold onto" the snow and create a microenvironment that gives them a surprising amount of protection from the wind.

I'm now going back five months to the hike I made up Adams in July and look at some pictures of the felsenmeer again. This is a photo of the summit of Mt. Adams taken on the northwest side of the summit cone. These large and small blocks of schist are lying directly on the bed rock. Some are stacked up on top of others.

This is the southeast side of the summit of Mt. Adams, the "warmer side" with the black spruce (Picea marinara) happily growing in this extreme alpine environment at 5781 feet. Notice the soil cells with the diapensia-sedge-moss communities that are also well developed on this extreme site. But more interesting is the jumble of blocks of schist that comprise the summit itself. They are stacked on top of each other as if dumped from a truck. If there was a clean, smooth ledge here when the ice sheet melted below summit level that was then fractured by an extreme period and magnitude of frost how did the blocks end up stacked up? Solifluction, by itself, wouldn't have the energy required to lift these blocks to stack them like this.

The ferocity of the frost that must have occurred after the ice sheet honed the mountains down to a smooth ledge of bed rock and then melted away must have been extreme. It would have had to occur after the ice sheet had melted considerably. One theory speculated that the frost action occurred during Younger Dryas (YD) event that featured several hundred years of extremely cold weather. Part of the theory is that the YD occurred because of a Deglaciation Climate Reversal (DCR) that occurred about 14,000 years ago that was triggered by massive amounts of fresh water re-entering the oceans during the melting of the Wisconsian ice sheet. Mean temperatures may have dropped quickly by several digits, as much as 15 degrees (C) based on ice core samples in Greenland. The YD certainly could have caused the magnitude of frost necessary and for a great length of time and it would also have increased solifluction markedly so it may be the event that formed the felsenmeer. (One way to look at this is that in a round about way the Wisconsian ice sheet caused the frost, which caused the mantel to fracture and produce the felsenmeer.)

Then looking due west towards Mt. Sam Adams (on the left in the near distance) the felsenmeer spreads out on either side of a slight ridge that runs west from the summit. Again we see a huge mass of rocks running for a half mile or so, randomly sized, all weathered and crusted with green and gray lichens. They are indeed prehistoric but are they just remnants of the old "skin", the mantel of bedrock that covered the post-glacial landscape? Could the ridge have been higher before it began to fracture? The ridge itself is bedrock, Littleton Schist, and is the likely source of most of the felsenmeer we see in immediate foreground of the photo.

At the end of the ridge coming down from the summit of Adams we come to this plateau. The felsenmeer doesn't end here even though it is a gentle slope. You can see what Goldthwait decribes as the soil cells and net-like formation of randomly sized rocks around these cells. Mt. Sam Adams, in the background, is 5585 feet in altitude. It looks like it is actively crumbling in several places. You can see the bedrock portruding upwards and the loose blocks of schist assembled below these points. Blocks are strewn across the plateau and some are stacked on top of each other. Two definite mechanisms created this landscape. Frost action caused fracturing of the bedrock formations, either outcrops or continuous ledge. Gravity cause the blocks to roll from the peak and ridges and formed slag piles like you see at quarries. On the plateau there is evidence of solifluction moving blocks into tightly formed "clumps". The only thing missing is the frost because, evidently, the frosts that occur in the current epoch are not anything like the frosts that caused this quarrying and solifluction. It might be reasonable to say that the frost that created the felsenmeer was intense but it also occurred more often in an average year then frosts do now. In other words, perhaps, due to longer fall and spring seasons with fairly cold temperatures and shorter summers, there was more frost activity, generally, in the alpine zone.

Mt. Jefferson from Adams to show the extent and location of most of the felsenmeer which cloaks the north and west side of the mountain with a feature somewhat like the "block glaciers" of Kings Ravine and Ravine of the Castles to the north and west of Mt. Adams. The block glaciers in those ravine are so called because they are massive areas of rock covering very steep terrrain and look like they were once moving like an ice glacier in a downward path from the higher peaks. The rock glacier in Kings Ravine includes huge boulders of schist that may have ridden piggy back on the melting glacial ice sheet in order to become lodged where they are today. On Jefferson the felsenmeer extends all the way down to the floor of Jefferson Ravine. There are relatively large areas of felsenmeer on the east face of Jefferson as well.

Mt. Madison from the Gulfside Trail in a photo taken about 50 years ago. Compare it to the one taken from here on 11-07-09 back at the beginning of this blog section and see if the krummholz has changed in any way area wise, or in altitude.

Mt. Madison from J. Q Adams taken in 1967. Madison Spring Hut is down in the lower left hand corner and the Carter Range is in the background to the right.

If we paint a picture, then, based on Goldthwait's description of the final years of the glacial ice sheet the landscape includes the high summits poking up out of the ice sheets resembling islands. These islands, or Nunataks, had somewhat smooth surfaces of polished bedrock which in the White Mountains would be granite in most places and schist across the Presidential Range. The bedrock is covered with detritus left by the ice sheet including tons of glacial "till" that included sand and gravel, and thousands of glacial "erratics" dumped out of the melting ice. Erratics (also part of the till) are represented by pebbles, stones and, in some cases, boulders weighing thousands of tons. Some erratics are round and smooth like river stones, some are rougher because they were lodged higher up in the ice or didn't travel as far as others. Some traveled in the ice a few hundred yards and some for a dozen or so miles from their points of origin. Goldthwait had a small collection of erratics he and his graduate students found across the Presidentials that are now at the Mt. Washington Observator Museum. One, my favorite, is a pink ball of Scrag granite that weighs 3 or 4 pounds and that came from Jefferson, a few miles away.

Then, even before the ice sheet is completely melted, an event occurs causing frost of a magnitude that has not occurred since. The frost causes fracturing (or quarrying of the solid bedrock surfaces everywhere that the mountain's summits are protruding up through the ice sheet. The frost also causes intense, on-going solifluction in the nascent soils that have been evolving from the till and from weathering of the bedrock.

For a period of years, perhaps a thousand years or more, the upper surface of the mountains, the mantel, is going through a profound change and a new landscape is evolving as the smooth rock breaks into large and small blocks that either stay in place where they were or they move a few inches, or yards, or roll down the mountain some distance.

I'm still impressed with the enormous mass of the blocks and have questions not answered by Goldthwait's summary. As the summits began to appear above the melting ice, forming Nunataks, were they higher then they are today by 25 or 30 feet? Has all the quarrying by the frost lowered the altitude of some of the highest ridges? If you could put the blocks back where they came from (reverse the film so to speak) would they just form a mantel of surface bedrock 3 or 4 feet thick? Or, would they add height to the existing summits?

When I look at the above this photo of Madison (taken in 1967) it's possible, because of the angle of sunlight, to see the folds of Littleton Schist arching up towards the south. The blocks of schist emanating from those exposed folds is all about. Some of it sits close to the bedrock and some has spilled downwards towards the hut. The summit is an outcropping of one of the folds and in this photo, the next photo up of Madison in shadow and the picture taken on this trip, 11-07-09, may present evidence that the summit, after the ice shrank away from the upper part of the mountain, may have lost some of it's height due to the quarrying along the summit ridge and it might explain how the existing felsenmeer, on both Madison, Adams and Jefferson, moved down the mountain and also how the blocks tumbled into their present placement stacked up on each other as many of them are.

I felt like it was getting very late in the afternoon because of the light. A high layer of clouds continued to move across the range from the northwest and the temperature continued to drop by 10 degrees or more so I head back to Madison Hut on the Gulfside Trail.

Before descending to the hut I went out to the parapet on the Air Line Trail where there's a spectacular view down into Kings Ravine. Mt. Adams is to the left and that's Mt. Sam Adams on the left center skyline. (The other bump on the skyline to the right is called "Mt. Adams 4" on some maps.) The ledge in the lower left corner of the photo is part of what is referred to as the "bulkhead" and it's located on the left side of the Kings Ravine headwall.

This photo (taken in July 1969) shows the bulkhead from a vantage point further down the Air Line Trail below the "knife edge". That's J.Q Adams in the center and Mt. Adams to the right. From this angle the bulkhead is impressive as are the massifs of both J.Q. and Adams. You can "feel" how the bedrock "flows" upwards in a fold that has then been cutoff along the highest ridge by the glacial ice sheet(s).

From still another angle you can see this close up the bulkhead which represents the bedrock and may be similar in "look and feel" to what the surface of the entire range was like as the peaks emerged above the ice sheet.

This couloir is the route the Chemin des Dame Trail descends from the Air Line Trail to the floor of Kings Ravine. It is also a boulder path, a stair way, constucted of blocks of schist that have cleaved off the bulkhead over a long period of time.

Close by is this "gendarme" located at the top of the knife edge portion of the Air Line Trail (and pretty much why it called the Airline). From here it's obvious that the loose, cleaving schist on this promontory is tumbling, bit by bit, down into the ravine below. This is called down wasting (as is the making of the felsenmeer itself) and it's likely going on today thanks to gravity.

Looking down at the floor of Kings Ravine with its extensive boulder field. The mass of boulders has been referred to as a "rock glacier" by the Goldthwaits and others. To some it has traveled too far down this cirque to have just tumbled there so it is called a "glacier", a stream of rocks from above that was pushed (but stopped long ago) by its own mass down the mountain like a glacier. Varying theories of how the pile of down wasted rock got so far down the ravine include one by Richard Goldthwait that I favor which is that the melting ice sheet carried rocks of all sizes including massive boulders in "piggy back" fashion down the side of the mountain finally depositing all the detritus at the far end of the cirque. Before the huts had refrigerators the Madison Hut croos would retrieve ice from the caves that exist in this so-called rock glacier to make ice cream.

Another example of this idea of "rock glaciers" is on the southwest side of Carter Dome where broken rock has created a glacier-like stream of rock that extends down into Carter Notch. The terminus of this stream is often referred to as the 'ramparts' and it is laced with caves that sometimes have ice in them all summer. On the Wildcat Mountain side of Carter Notch there are also caves that the Carter Hut croos used to store perishable food during the summer. Some of the caves are quite deep and extensive.

Back on the Gulfside Trail this is a view of the north side of J.Q. Adams with the massive boulders that look like they're just hanging there on a thread and capable of smashing down at any moment. Again there's the sense of there being enormous energy in all that mass. When the felsenmeer was formed a lot of energy was released during the breaking up of the slabs of bedrock and there's still a lot of energy there.

This is pretty much the extent of what we know about felsenmeer:

It's derived from the local rock. (glacial erratics of various pedigrees, shapes and sizes are mixed in with the felsenmeer. The erratics are relatively local.)

The vast areas of lichen encrusted felsenmeer that we see on the northern peaks of the Presidentials is made up of millions and millions of separate boulders that were once the top 3 or 4 feet of original bedrock which in this case was predominantly Littelton Schist.

Schist, a metamorphic rock, is more likely to fracture into blocks and form felsenmeer than igneous rocks like granite.

The felsenmeer is probably more than 10,000 years old. The rock mantel, meaning the uppermost part of the bedrock that makes up the mass of the Presidentials, that broke up to form the felsenmeer had been smoothed by the Wisconsian glacial ice sheet, or continental glacier, which completely covered the White Mountains for 40,000 years.

The felsenmeer was formed as the mantel, or surface of the bedrock, was subjected to intense frosts over a long period of time, maybe as long as 1,000 years, that began when the glacial ice was melting downwards from the higher peaks. The frost caused "quarrying" (cutting or splitting:breakage) of the surface rock. The cold temperatures may have been associated with a the Young Dryas event beginning about 14000 years ago which, according to theory, was a climatic change sometimes referred to as "the little ice age."

The energy (work) involved in the breaking up of the bedrock came from a consistently cold, damp climate associated with a widespread climate change that caused intense frost to form in higher elevations of the white mountains. The frost, through on-going freeze-thaw cycles caused existing cracks in the bedrock slabs to expand until the slabs broke into smaller blocks.

The felsenmeer formed, generally, only above 5300 feet in elevation in the White Mountains (according to R. Goldthwait) . It's possible that the Wisconsinan ice sheet had not down wasted below the 5000 foot level at the time, or because of the intense cold was not down wasting at all.

The activity associated with the formation of the felsenmeer on the Presidential Range has been dormant for thousands of years. While there is inevitably some frost splitting of rock occurring throughout the White Mountains during particularly cold winters there is relatively little movement in the felsenmeer at this time.

"Mass Wasting" is a term used to describe the inexorable process by which all mountains eventually comply with gravity and wash, wear, erode, and/or fall down. This includes large dramatic events like huge landslides and small, barely noticeable events like a small bit of rock breaking off an outcropping and tumbling down a few yards into some bushes. It's like a clock ticking. It usuallys takes hundreds and hundred of millions of years for a mountain to be "born" (called orogenesis) and then mass waste back to a level plain again. The felsenmeer represents a stage in the mass wasting of the White Mountains and their transformation to smaller and smaller particiles eventually becoming small enough to wash away.

My last thoughts revolve around the part the felsenmeer plays in the natural history of the White Mountains. The story of the felsenmeer is a signifcant chapter in the geologic history of the mountains and it still has a signficant presence, e.g. it represents a dramatic change in the landscape. Continuing research will shed more light on how old the quarried blocks are and may provide valuable information about the climate that caused the transformation and, in turn, give us clues about the period of time immediately following the down wasting of the ice sheet.

For the moment the felsenmeer represents a very unique environment occurring near the ground and all across the range. It both hinders and supports attempts by vegetation to colonize the alpine areas, and it changes the way moisture moves on the ground and changes in the atmosphere close to the ground. It plays a significant role in the growth and long term stability of the krummholz which in turn plays a role in soil development and stability, moisture retention, shelter for birds, mammals, insects, etc. So there's quite a bit to think about.

Here's someone that dresses like I do! He looked quite relaxed so I asked him what time it was expecting him to say 3:30 or 4 pm, but he said it was only 1 pm. I'd completely lost track of time!

Still, I had a hut related reunion dinner to go to at the Highland Center in Crawford Notch that was slated to begin at 4:30 pm so I decided to go down at a leisurely pace. I took one last look up at J.Q. Adams and put my pack back on.

Madison looks Christmassy with the snow and the balsams. When the hut was closed for the season in September the windows were shuttered and the doors replaced with solid steel plate to prevent hikers from breaking into the hut during the winter and early spring. All the huts have suffered massive damage from vandals as well as hikers in distress who break in to find shelter. The cost of repairing the damage is astronomical. "Hut Checking" croos are sent out all winter as a preventive measure as well, and to report damage before others capitalize on it and make it worse. This is not a new phenomenon. I often worked for room and board at Pinkham Notch in the early 60s by going out hut checking in the winter and had some nasty experiences with vandals breaking into huts who, when caught in the act, threatened me with physical assault and, once or twice, with guns. Luckily that hasn't happened to any of the hut checkers in a long time

1 comment:

Philip Werner said...

I am always completely mesmerized by your posts and pictures. Thanks!