The first glacial traces that I noticed in the basin are on the Wassuck, Augusta, and Toyabe ranges, consisting of ridges16 and canyons, whose trends, contours, and general sculpture are in great part specifically glacial, though deeply blurred by subsequent denudation17. These discoveries were made during the summer of 1876-77. And again, on the 17th of last August, while making the ascent18 of Mount Jefferson, the dominating mountain of the Toquima range, I discovered an exceedingly interesting group of moraines, canyons with V-shaped cross sections, wide neve amphitheatres, moutoneed rocks, glacier meadows, and one glacier lake, all as fresh and telling as if the glaciers to which they belonged had scarcely vanished.
The best preserved and most regular of the moraines are two laterals about two hundred feet in height and two miles long, extending from the foot of a magnificent canyon9 valley on the north side of the mountain and trending first in a northerly direction, then curving around to the west, while a well-characterized terminal moraine, formed by the glacier towards the close of its existence, unites them near their lower extremities20 at a height of eighty-five hundred feet. Another pair of older lateral19 moraines, belonging to a glacier of which the one just mentioned was a tributary21, extend in a general northwesterly direction nearly to the level of Big Smoky Valley, about fifty-five hundred feet above sea level.
Four other canyons, extending down the eastern slopes of this grand old mountain into Monito Valley, are hardly less rich in glacial records, while the effects of the mountain shadows in controlling and directing the movements of the residual22 glaciers to which all these phenomena belonged are everywhere delightfully23 apparent in the trends of the canyons and ridges, and in the massive sculpture of the neve wombs at their heads. This is a very marked and imposing24 mountain, attracting the eye from a great distance. It presents a smooth and gently curved outline against the sky, as observed from the plains, and is whitened with patches of enduring snow. The summit is made up of irregular volcanic26 tables, the most extensive of which is about two and a half miles long, and like the smaller ones is broken abruptly27 down on the edges by the action of the ice. Its height is approximately eleven thousand three hundred feet above the sea.
A few days after making these interesting discoveries, I found other well-preserved glacial traces on Arc Dome28, the culminating summit of the Toyabe Range. On its northeastern slopes there are two small glacier lakes, and the basins of two others which have recently been filled with down-washed detritus. One small residual glacier lingered until quite recently beneath the coolest shadows of the dome, the moraines and neve-fountains of which are still as fresh and unwasted as many of those lying at the same elevation29 on the Sierra—ten thousand feet—while older and more wasted specimens30 may be traced on all the adjacent mountains. The sculpture, too, of all the ridges and summits of this section of the range is recognized at once as glacial, some of the larger characters being still easily readable from the plains at a distance of fifteen or twenty miles.
The Hot Creek31 Mountains, lying to the east of the Toquima and Monito ranges, reach the culminating point on a deeply serrate ridge15 at a height of ten thousand feet above the sea. This ridge is found to be made up of a series of imposing towers and pinnacles32 which have been eroded33 from the solid mass of the mountain by a group of small residual glaciers that lingered in their shadows long after the larger ice rivers had vanished. On its western declivities are found a group of well-characterized moraines, canyons, and roches moutonnees, all of which are unmistakably fresh and telling. The moraines in particular could hardly fail to attract the eye of any observer. Some of the short laterals of the glaciers that drew their fountain snows from the jagged recesses34 of the summit are from one to two hundred feet in height, and scarce at all wasted as yet, notwithstanding the countless36 storms that have fallen upon them, while cool rills flow between them, watering charming gardens of arctic plants—saxifrages, larkspurs, dwarf37 birch, ribes, and parnassia, etc.—beautiful memories of the Ice Age, representing a once greatly extended flora38.
In the course of explorations made to the eastward39 of here, between the 38th and 40th parallels, I observed glacial phenomena equally fresh and demonstrative on all the higher mountains of the White Pine, Golden Gate, and Snake ranges, varying from those already described only as determined40 by differences of elevation, relations to the snow-bearing winds, and the physical characteristics of the rock formations.
On the Jeff Davis group of the Snake Range, the dominating summit of which is nearly thirteen thousand feet in elevation, and the highest ground in the basin, every marked feature is a glacier monument—peaks, valleys, ridges, meadows, and lakes. And because here the snow-fountains lay at a greater height, while the rock, an exceedingly hard quartzite, offered superior resistance to post-glacial agents, the ice-characters are on a larger scale, and are more sharply defined than any we have noticed elsewhere, and it is probably here that the last lingering glacier of the basin was located. The summits and connecting ridges are mere41 blades and points, ground sharp by the glaciers that descended42 on both sides to the main valleys. From one standpoint I counted nine of these glacial channels with their moraines sweeping43 grandly out to the plains to deep sheer-walled neve-fountains at their heads, making a most vivid picture of the last days of the Ice Period.
I have thus far directed attention only to the most recent and appreciable44 of the phenomena; but it must be borne in mind that less recent and less obvious traces of glacial action abound45 on ALL the ranges throughout the entire basin, where the fine striae and grooves46 have been obliterated47, and most of the moraines have been washed away, or so modified as to be no longer recognizable, and even the lakes and meadows, so characteristic of glacial regions, have almost entirely48 vanished. For there are other monuments, far more enduring than these, remaining tens of thousands of years after the more perishable records are lost. Such are the canyons, ridges, and peaks themselves, the glacial peculiarities49 of whose trends and contours cannot be hid from the eye of the skilled observer until changes have been wrought50 upon them far more destructive than those to which these basin ranges have yet been subjected.
It appears, therefore, that the last of the basin glaciers have but recently vanished, and that the almost innumerable ranges trending north and south between the Sierra and the Wahsatch Mountains were loaded with glaciers that descended to the adjacent valleys during the last glacial period, and that it is to this mighty51 host of ice streams that all the more characteristic of the present features of these mountain ranges are due.
But grand as is this vision delineated in these old records, this is not all; for there is not wanting evidence of a still grander glaciation extending over all the valleys now forming the sage plains as well as the mountains. The basins of the main valleys alternating with the mountain ranges, and which contained lakes during at least the closing portion of the Ice Period, were eroded wholly, or in part, from a general elevated tableland, by immense glaciers that flowed north and south to the ocean. The mountains as well as the valleys present abundant evidence of this grand origin.
The flanks of all the interior ranges are seen to have been heavily abraded52 and ground away by the ice acting25 in a direction parallel with their axes. This action is most strikingly shown upon projecting portions where the pressure has been greatest. These are shorn off in smooth planes and bossy53 outswelling curves, like the outstanding portions of canyon walls. Moreover, the extremities of the ranges taper54 out like those of dividing ridges which have been ground away by dividing and confluent glaciers. Furthermore, the horizontal sections of separate mountains, standing35 isolated55 in the great valleys, are lens-shaped like those of mere rocks that rise in the channels of ordinary canyon glaciers, and which have been overflowed56 or pastflowed, while in many of the smaller valleys roches moutonnees occur in great abundance.
Again, the mineralogical and physical characters of the two ranges bounding the sides of many of the valleys indicate that the valleys were formed simply by the removal of the material between the ranges. And again, the rim57 of the general basin, where it is elevated, as for example on the southwestern portion, instead of being a ridge sculptured on the sides like a mountain range, is found to be composed of many short ranges, parallel to one another, and to the interior ranges, and so modeled as to resemble a row of convex lenses set on edge and half buried beneath a general surface, without manifesting any dependence58 upon synclinal or anticlinal axes—a series of forms and relations that could have resulted only from the outflow of vast basin glaciers on their courses to the ocean.
I cannot, however, present all the evidence here bearing upon these interesting questions, much less discuss it in all its relations. I will, therefore, close this letter with a few of the more important generalizations59 that have grown up out of the facts that I have observed. First, at the beginning of the glacial period the region now known as the Great Basin was an elevated tableland, not furrowed60 as at present with mountains and valleys, but comparatively bald and featureless.
Second, this tableland, bounded on the east and west by lofty mountain ranges, but comparatively open on the north and south, was loaded with ice, which was discharged to the ocean northward61 and southward, and in its flow brought most, if not all, the present interior ranges and valleys into relief by erosion.
Third, as the glacial winter drew near its close the ice vanished from the lower portions of the basin, which then became lakes, into which separate glaciers descended from the mountains. Then these mountain glaciers vanished in turn, after sculpturing the ranges into their present condition.
Fourth, the few immense lakes extending over the lowlands, in the midst of which many of the interior ranges stood as islands, became shallow as the ice vanished from the mountains, and separated into many distinct lakes, whose waters no longer reached the ocean. Most of these have disappeared by the filling of their basins with detritus from the mountains, and now form sage plains and "alkali flats."
The transition from one to the other of these various conditions was gradual and orderly: first, a nearly simple tableland; then a grand mer de glace shedding its crawling silver currents to the sea, and becoming gradually more wrinkled as unequal erosion roughened its bed, and brought the highest peaks and ridges above the surface; then a land of lakes, an almost continuous sheet of water stretching from the Sierra to the Wahsatch, adorned62 with innumerable island mountains; then a slow desiccation and decay to present conditions of sage and sand.
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1
perishable
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| adj.（尤指食物）易腐的，易坏的 | |
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grooved
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| v.沟( groove的过去式和过去分词 )；槽；老一套；（某种）音乐节奏 | |
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glacier
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| n.冰川，冰河 | |
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sediments
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| 沉淀物( sediment的名词复数 )； 沉积物 | |
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detritus
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| n.碎石 | |
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derived
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| vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取 | |
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arid
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| adj.干旱的；(土地)贫瘠的 | |
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sage
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| n.圣人，哲人；adj.贤明的，明智的 | |
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canyon
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| n.峡谷，溪谷 | |
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canyons
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| n.峡谷( canyon的名词复数 ) | |
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blurred
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| v.（使）变模糊( blur的过去式和过去分词 )；（使）难以区分；模模糊糊；迷离 | |
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12
remains
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| n.剩余物，残留物；遗体，遗迹 | |
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phenomena
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| n.现象 | |
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glaciers
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| 冰河，冰川( glacier的名词复数 ) | |
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15
ridge
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| n.山脊；鼻梁；分水岭 | |
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ridges
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| n.脊( ridge的名词复数 )；山脊；脊状突起；大气层的)高压脊 | |
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17
denudation
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| n.剥下；裸露；滥伐；剥蚀 | |
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ascent
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| n.(声望或地位)提高；上升，升高；登高 | |
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lateral
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| adj.侧面的，旁边的 | |
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extremities
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| n.端点( extremity的名词复数 )；尽头；手和足；极窘迫的境地 | |
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tributary
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| n.支流；纳贡国；adj.附庸的；辅助的；支流的 | |
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residual
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| adj.复播复映追加时间；存留下来的，剩余的 | |
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23
delightfully
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| 大喜，欣然 | |
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imposing
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| adj.使人难忘的，壮丽的，堂皇的，雄伟的 | |
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acting
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| n.演戏，行为，假装；adj.代理的，临时的，演出用的 | |
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volcanic
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| adj.火山的；象火山的；由火山引起的 | |
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abruptly
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| adv.突然地，出其不意地 | |
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dome
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| n.圆屋顶，拱顶 | |
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elevation
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| n.高度；海拔；高地；上升；提高 | |
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30
specimens
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| n.样品( specimen的名词复数 )；范例；（化验的）抽样；某种类型的人 | |
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creek
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| n.小溪，小河，小湾 | |
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32
pinnacles
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| 顶峰( pinnacle的名词复数 )； 顶点； 尖顶； 小尖塔 | |
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eroded
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| adj. 被侵蚀的，有蚀痕的 动词erode的过去式和过去分词形式 | |
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34
recesses
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| n.壁凹( recess的名词复数 )；（工作或业务活动的）中止或暂停期间；学校的课间休息；某物内部的凹形空间v.把某物放在墙壁的凹处( recess的第三人称单数 )；将（墙）做成凹形，在（墙）上做壁龛；休息，休会，休庭 | |
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35
standing
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| n.持续，地位；adj.永久的，不动的，直立的，不流动的 | |
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countless
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| adj.无数的，多得不计其数的 | |
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dwarf
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| n.矮子，侏儒，矮小的动植物；vt.使…矮小 | |
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38
flora
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| n.(某一地区的)植物群 | |
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39
eastward
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| adv.向东；adj.向东的；n.东方，东部 | |
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determined
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| adj.坚定的；有决心的 | |
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mere
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| adj.纯粹的；仅仅，只不过 | |
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42
descended
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| a.为...后裔的，出身于...的 | |
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43
sweeping
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| adj.范围广大的，一扫无遗的 | |
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44
appreciable
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| adj.明显的，可见的，可估量的，可觉察的 | |
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45
abound
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| vi.大量存在；(in，with)充满，富于 | |
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46
grooves
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| n.沟( groove的名词复数 )；槽；老一套；（某种）音乐节奏v.沟( groove的第三人称单数 )；槽；老一套；（某种）音乐节奏 | |
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47
obliterated
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| v.除去( obliterate的过去式和过去分词 )；涂去；擦掉；彻底破坏或毁灭 | |
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48
entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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49
peculiarities
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| n. 特质, 特性, 怪癖, 古怪 | |
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50
wrought
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| v.引起；以…原料制作；运转；adj.制造的 | |
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51
mighty
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| adj.强有力的；巨大的 | |
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52
abraded
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| adj.[医]刮擦的v.刮擦( abrade的过去式和过去分词 )；（在精神方面）折磨（人）；消磨（意志、精神等）；使精疲力尽 | |
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53
bossy
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| adj.爱发号施令的，作威作福的 | |
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54
taper
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| n.小蜡烛，尖细，渐弱；adj.尖细的；v.逐渐变小 | |
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55
isolated
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| adj.与世隔绝的 | |
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56
overflowed
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| 溢出的 | |
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57
rim
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| n.(圆物的)边，轮缘；边界 | |
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58
dependence
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| n.依靠，依赖；信任，信赖；隶属 | |
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59
generalizations
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| 一般化( generalization的名词复数 )； 普通化； 归纳； 概论 | |
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60
furrowed
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| v.犁田，开沟( furrow的过去式和过去分词 ) | |
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61
northward
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| adv.向北；n.北方的地区 | |
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62
adorned
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| [计]被修饰的 | |
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