This way of drawing the line is significantly problematized by theemergence of female-friendly and feminist pornography. Examples arefilms like All About Anna (2005,dir. Jessica Nilsson), Molly Kiely's graphicnovel That Kind of Girl (1999),or Dirty Diaries, a collection of Swedishmovie shorts (2009). Mutual pleasure and consent areabsolutely key in these pornographic works which seem to exhibit noneof the moral flaws manifest in mainstream pornography (noexploitation, objectification, or eroticization of genderinequality). What is more, in rejecting sexual repression,self-oppression, and hypocrisy, these works are often said to have apositive, consciousness-raising force (Willis 1995; Taormino et al.2013.
After the bridge, the track heads downhill and the shrubland turns into forest. It\u2019s mountain beech, a low canopy of twisted trees growing at the limit of what they can survive. Climate change crosses my mind. As temperatures warm, treelines will rise, a line of green creeping up the mountains. It may squeeze out some of our native alpine plants, those which grow above the treeline, as their habitat moves higher and higher. It\u2019s another thing I tuck away in the back of my mind, something I want to research more.
I walk down a set of steep steps, then come around a corner and into shrubland again. I hear the rush of the falls. There\u2019s a twenty metre drop, and the water isn\u2019t simply trickling over the edge. It pours through a narrow gap and the force of the flow carries it into a graceful arc before it falls into a pool below. I stand and watch for a while, and I would stay longer but the air is cold and it\u2019s late in the day. So I follow the course of the stream to another bridge and the second part of the falls. The water takes a sharp bend where it has gouged a smooth indentation in the rock and plunges into a deep gorge. The water is so clear I can see the texture of the rock. But the pleasure is marred by a chip packet which someone has dropped. It\u2019s caught in part of a tree branch below me, out of reach.
When Nature lifted the ice-sheet from the mountains she maywell be said not to have turned a new leaf, but to have made anew one of the old. Throughout the unnumbered seasons of the glacialepoch the range lay buried, crushed, and sunless. In the stupendousdenudation to which it was then subjected, all its pre-glacialfeatures disappeared Plants, animals, and landscapes were wipedfrom its flanks like drawings from a blackboard, and the vastpage left smooth and clean, to be repictured with young life andthe varied and beautiful inscriptions of water, snow, and theatmosphere.The variability in hardness, structure, and mineralogical compositionof the rocks forming the present surface of the range has givenrise to irregularities in the amount of post-glacial denudationeffected in different portions, and these irregularities havebeen greatly multiplied and augmented by differences in the kindand intensity of the denuding forces, and in the length of timethat different portions of the range have been exposed to theiraction. The summits have received more snow, the foothills morerain, while the middle region has been variably acted upon byboth of these agents. Again, different portions are denuded ina greater or less degree according to their relations to level.The bottoms of trunk valleys are swept by powerful rivers, thebranches by creeks and rills, while the intervening plateaus andridges are acted upon only by thin, feeble currents, silent andnearly invisible. Again some portions of the range are subjectedevery winter to the scouring action of avalanches, while othersare entirely beyond the range of such action. But the most influentialof the general causes that have conspired to produce irregularityin the quantity of post-glacial denudation is the differencein the length of time during which different portions of the rangehave been subjected to denuding agents. The ice-sheet meltedfrom the base of the range tens of thousands of years ere it meltedfrom the upper regions. We find, accordingly, that the foothillregion is heavily weathered and blurred, while the summit, exceptingthe peaks, and a considerable portion ofthe middle region remain fresh and shining as if they had neversuffered from the touch of a single storm.Perhaps the least known among the more outspoken agents of mountaindegradation are those currents of eroding rock called avalanches.Those of the Sierra are of all sizes, from a few sand-grainsor crystals worked loose by the weather and launched to the bottomsof cliffs, to those immense earthquake avalanches that thunderheadlong down amid fire and smoke and dust, with a violence thatshakes entire mountains. Many avalanche-producing causes,as moisture, temperature, winds, and earthquakes are exceedinglyvariable in the scope and intensity of their action. During thedry, equable summers of the middle region, atmospheric distintegrationgoes silently on, and many a huge mass is made ready to be advantageouslyacted upon by the first winds and rains of winter. Inclined surfacesare then moistened and made slippery, decomposed joints washedout, frost-wedges driven in, and the grand avalanche stormbegins. But though these stone-storms occur only in winter,the attentive mountaineer may have the pleasure of witnessingsmall avalanches in every month of the year. The first warningof the bounding free of a simple avalanche is usually a dull muffledrumble, succeeded by a ponderous crunching sound; then perhapsa single huge block weighing a hundred tons or more may be seenwallowing down the face of a cliff, followed by a train of smallerstones, which are gradually left behind on account of the greaterrelative resistance they encounter as compared with their weight.The eye may therefore follow the large block undisturbed, notingits awkward, lumbering gestures as it gropes its way through theair in its first wild journey, and how it is made to revolve likea star upon its axis by striking on projecting portions of thewalls while it pursues the grand smooth curves of general descent.Where it strikes a projecting boss it gives forth an intense gaspingsound, which, coming through the darkness of a storm-night, isindescribably impressive; and when at length it plunges into thevalley, the ground trembles as if shaken by an earthquake.On the 12th of March, 1873, I witnessed a magnificent avalanchein Yosemite Valley from the base of the second of the Three Brothers.A massive stream of blocks bounded from ledge to ledge and plungedinto the talus below with a display of energy inexpressibly wildand exciting. Fine gray foam-dust boiled and swirled alongits path, and gradually rose above the top of the cliff, appearingas a dusky cloud on the calm sky. Unmistakable traces of similaravalanches are visible here, probably caused by the decompositionof the feldspathic veins with which the granite is interlaced.Earthquakes, though not of frequent occurrence in the Sierra,are powerful causes of avalanches. Many a lofty tower and impendingbrow stood firm through the storms of the first post-glacialseasons. Torrents swept their bases, and winds and snows slippedglancingly down their polished sides, without much greater erosiveeffect than the passage of cloud-shadows. But at length thenew-born mountains were shaken by an earthquake-storm,and thousands of avalanches from cañon walls and mountainsides fell in one simultaneous crash. The records of this firstpost-glacial earthquake present themselves in every cañonand around the bases of every mountain summit that I have visited;and it is a fact of great geological interest that to it alonemore than nine-tenths of all the cliff taluses which formso strikingly a characteristic of cañon scenery are due.The largest of these earthquake taluses are from 500 to 1,000feet in height, and are timbered with spruce, pine, and live-oakover their entire surfaces, showing that they have not been disturbedsince their formation, either by denudation or accessions of freshmaterial.The earthquake which destroyed the village of Lone Pine, in March,1872, shook the Sierra with considerable violence, giving riseto many new taluses, the formation of one of which I was so fortunateas to witness.The denuding action of avalanches is not unlike that of water-torrents.They are frequently seen descending the summit peaks, flowingin regular channels, the surfaces of which they erode by strikingoff large chips and blocks, as well as by wearing off sand anddust.A considerable amount of grinding also goes on in the body ofthe avalanche itself, reducing the size of the masses, and preparingthem for the action of other agents. Some avalanches hurl theirdetritus directly into the beds of streams, thus bringingit under the influence of running water, by which a portion ofit is carried into the ocean.The range of rock avalanches, however produced, is restrictedwithin comparatively narrow bounds. The shattered peaks are constantfountains, but the more powerful mountain-shaking avalanchesare confined to the edges of deep cañons in a zone twelveor fifteen miles wide, and gradually merge into land-slipsalong their lower limits.Large rock avalanches pour freely through the air from a heightof hundreds or thousands of feet, and on striking the bottom ofthe valley are dashed into a kind of coarse stone foam. Or, theymake the descent in several leaps, or rumble over jagged inclinesin the form of cascades. But in any case they constitute currentsof loose-flowing fragments. Landslips, on the contrary, slipin one mass, and, unless sheer cliffs lie in their paths, maycome to rest right-side up and undivided. There is also amarked difference in their geographical distribution, land-slipsbeing restricted to deeply eroded banks and hillsides of the lowerhalf of the range, beginning just where rock avalanches cease.Again, the material of land-slips is chiefly fine soil anddecomposing boulders, while that of rock avalanches is mostlyof unweathered angular blocks.
Fig. 1Let Figure 1 represent a section across a valley in which morainematter, A, is deposited upon the inclined bed-rock, B B B.Now, strong young moraine material deposited in this way, in akind of rude masonry, always rests, or is capable of resting,at a much steeper angle than the same material after it has grownold and rotten. If a poultice of acid mud be applied to a strongboulder, it will not be much affected in an hour orday, but if kept on for a few thousands or tens of thousands ofyears, it will at length soften and crumble. Now, Nature thuspatiently poultices the boulders of the moraine banks under consideration.For many years subsequent to the close of the ice period verylittle acid for this purpose was available, but as vegetationincreased and decayed, acids became more plentiful, and boulderdecomposition went on at an accelerated rate, until a degree ofweakness was induced that caused the sheerest portions of thedeposits, as A B D (Fig. 1), to give way, perhaps when jarredby an earthquake, or when burdened with snow or rain, or partiallyundermined by the action of a stream.It appears, therefore, that the main cause of the first post-glaciallandslips is old age. They undoubtedly made their first appearancein moraine banks at the foot of the range, and gradually extendedupward to where, we now find them, at a rate of progress measuredby that of the recession of the ice-sheet, and by the durabilityof moraines and the effectiveness of the corroding forces broughtinto action upon them. In those portions of the Sierra where themorainal deposits are tolerably uniform in kindand exposure, the upper limits of the land-slip are seento stretch along the range with as great constancy of altitudeas that of the snow-line.The above-described species of land-slip is followedup the range by another of greater size, just as the differentforest trees follow one another in compliance with conditionsof soil and climate. After the sheer end the deposit (AB D, Fig. 1 ) has slipped, the whole mass may finally slipon the bed-rock by the further decomposition, not only ofthe deposit itself, but of the bed-rock on which it rests.Bed-rocks are usually more or less uneven. Now, it is plainthat when the inequalities B B B crumble by erosion, the massof the deposit will not be so well supported; moreover, the weightof the mass will continue to increase as its material is morethoroughly pulverized, because a greater quantity of moisturewill be required to saturate it. Thus it appears that the supportof moraine deposits diminishes, just as the necessity for greatersupport increases, until a slip is brought on.Slips of this species are often of great extent, the surface comprisingseveral acres overgrown with trees, perhaps moving slowly andcoming to rest with all their load of vegetation uninjured, leavingonly a yawning rent to mark their occurrence. Others break upinto a muddy disorderly flood, moving rapidly until the bottomof the wall is reached. Land-slides occur more frequentlyon the north than on the south sides of ridges because of thegreater abundance of weight-producing and decomposing moisture.One of the commonest effects of land-slips is the dammingof streams, giving rise to large accumulations of water, whichspeedily burst the dams and deluge the valleys beneath, sweepingthe finer detritus before them to great distances, andat first carry boulders tons in weight.The quantity of denudation accomplished by the Sierra land-slipsof both species is very small. Like rock-falls, they erodethe surface they slip upon in a mechanical way, and also bringdown material to lower levels, where it may be more advantageouslyexposed to the denuding action of other agents, and open scarswhereby rain-torrents are enabled to erode gullies; but thesum of the areas thus affected bears an exceedingly small proportionto the whole surface of the range.The part which snow avalanches play in the degradation of mountainsis simpler than that of free-falling or cascading rocks,or either species of land-slip; these snow avalanches beingexternal and distinct agents. Their range, however, is as restrictedas that of either of the others, and like them they only carrytheir detritus a short distance and leave it in heaps atthe foot of cliffs and steep inclines. There are three well-markedand distinct species of snow avalanche in the upper half of theSierra, differingwidely in structure, geographical distribution, and in the extentand importance of the geological changes they effect. The simplestand commonest species is formed of fresh mealy snow, and occursduring and a short time after every heavy snow-fall whereverthe mountain slopes are inclined at suitable angles. This speciesis of frequent occurrence throughout all the steep-flankedmountains of the summit of the range, where it reaches perfection,and is also common throughout the greater portion of the middleregion. Avalanches are the feeders of the glaciers, pouring downtheir dry mealy snow into the womb-amphitheaters, where itis changed to névé and ice. Unless distributedby storm-winds, they cascade down the jagged heights in regularchannels, and glide gracefully out over the glacier slopes inbeautiful curves; which action gives rise in summer to a mostinteresting and comprehensive system of snow-sculpture. Thedetritus discharged upon the surface of the glaciers formsa kind of stone-drift which is floated into moraines like thestraws and chips of rivers.Few of the defrauded toilers of the plain know the magnificentexhilaration of the boom and rush and outbounding energy of greatsnow avalanches. While the storms that breed them are in progress,the thronging flakes darken the air at noonday. Their muffledvoices reverberate through the gloomy cañons, but we tryin vain to catch a glimpse of their noble forms until rifts appearin the clouds, and the storm ceases. Then in cliff-walled valleyslike Yosemite we may witness the descent of half a dozen or moresnow avalanches within a few hours.The denuding power of this species of avalanche is not great,because the looseness of the masses allows them to roll and slipupon themselves. Some portions of their channels, however, presenta roughly scoured appearance, caused by rocky detritus borneforward in the under portion of the current. The avalanche is,of course, collected in a heap at the foot of the cliff, and onmelting leaves the detritus to accumulate from year toyear. These taluses present striking contrasts to those of rockavalanches caused by the first great pre-glacial earthquake.The latter are gray in color, with a covering of slow-growinglichens, and support extensive groves of pine, spruce, and live-oak;while the former, receiving additions from year to year, are keptin a raw formative state, neither trees nor lichens being allowedtime to grow, and it is a fact of great geological significancethat no one of the Yosemite snow avalanches, although they haveundoubtedly flowed in their present channels since the close ofthe glacial period, has yet accumulated so much débrisas some of the larger earthquake avalanches which were formedin a few seconds.The next species of avalanche in natural order is the annual one,composedof heavy crystalline snows which have been subjected to numerousalternations of frost and thaw. Their development requires a shadowedmountain side 9,000 or 10,000 feet high, inclined at such an anglethat loose fresh snow will lodge and remain upon it, and bearrepeated accessions throughout the winter without moving; butwhich, after the spring thaws set in, and the mountain side thusbecomes slippery, and the nether surface of the snow becomes icy,will then give way.One of the most accessible of the fountains of annual avalanchesis the northern slope of Cloud's Rest, above the head of the YosemiteValley. Here I have witnessed the descent of three within halfan hour. They have a vertical descent of nearly a mile on a smoothgranite surface. Fine examples of this species of avalanche mayalso be observed upon the north side of the dividing ridge betweenthe basins of Ribbon and Cascade