the grand canyon of arizona-第23节
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ll defined。 As the uplift continues； the cherty limestone and possibly the cross…bedded sandstone are both cut through； as the plateau slowly emerges。 Whether the process of uplift is slow or rapid； as soon as a stratum emerges； it becomes subject to the influences of weathering； and the uppermost strata appearing first； they are weathered most。 Hence the recession of the uppermost cliffs is greater than that of the cliffs lower down。 The differences in hardness and resistance to weathering are alone responsible for the step…like profile of cliffs and terraces。 The lower platform owes its width entirely to the rapid weathering and recession of the soft shales； which overlie the Tonto sandstones。 The red…wall limestone； on the other hand； remains standing out as a cliff because of its exceeding durability。
The Faults。 During the final uplift； the river cut through the Cambrian and Algonkian strata； and into the Granite Gorge as we find it to…day； and the process is still slowly going on。 During these various periods of uplift； there were other changes occurring。 Sometimes the uplift was uneven； certain parts of the plateau being lifted more rapidly than other parts； then occurred breaks in the strata； called faults。 There are a great number of these faults in the plateau country； most of them crossing the Canyon from north to south。 This faulting； as is readily seen； would produce cracks； and as the uneven uplift continued； the strata on one side of the crack would be lifted higher than the strata on the other side。 Or； the strata on one side of the crack would be uplifted； while the other would subside。
Bright Angel Fault。 El Tovar rests directly upon the strata affected by the Bright Angel Fault line。 On going down the Bright Angel Trail； one cannot fail to see； as he passes the tap of the cross…bedded sandstone； the break in the strata。 To the left it is fully one hundred and fifty to two hundred feet higher than it is on the right。 The same depression may be observed in driving out to Hopi； Point； or returning。 The stratum on which the road is made should be at the same level as the stratum on which El Tovar rests。
Fault at Bass Camp。 This fault is but one of a score or more on the plateau。 At Bass Camp there was a fault which displaced the strata on each side of the 〃break〃 to the extent of four thousand feet。 Later； another fault occurred； which readjusted the displacement somewhat； and reduced the difference to two thousand feet； yet left the evidences of the former wide divergence。 It was also during these uplift periods that the volcanic mountains of the region came into existence； as the San Francisco Range； Mounts Kendricks； Sitgreaves； Williams and Floyd on the south； and the UinkaretsMounts Trumbull； Logan； Emmaon the north。
Lava Flows。 In one place； south of Mount Emma； Powell's party saw where vast floods of lava had flowed from it into the river。 They declare that 〃a stream of molten rock has run up the Canyon three or four miles； and down； we know not how far。 The whole north side； as far as we can see； is lined with the black basalt； and high up on the opposite wall are patches of the same material； resting on the benches； and filling old alcoves and caves； and giving to the wall a spotted appearance。〃 All these volcanic mountains can be seen from Hopi or Yavapai points； near El Tovar。
The Algonkian Strata。 The Algonkian strata of the Grand Canyon are by far the most interesting； Major Powell was the first to call attention to their existence in his report of explorations of 1869…1872； and he discusses their origin and history as far as was possible with the small amount of data he had at hand。 Later Dr。 Charles D。 Walcott； his successor as Director of the United States Geological Survey； and now the Secretary of the Smithsonian Institution； spent a full winter in the heart of the Canyon； especially studying the unique formations。 Unique they are； for； though found elsewhere on the earth； they are exceedingly rare； and； up to this time； had received little study and were unknown and unnamed。 The area studied by Walcott lies at the very entrance to the Grand Canyon； near where the Marble Canyon and Little Colorado Canyon join the main one。 While the series cross the river and are a fine feature of Red Canyon Trail； the main study was done on the north side。 Dr。 Walcott thus locates the site of his studies： 〃This area； between 35 degrees 57 minutes and 36 degrees 17 minutes north latitude； and between 111 degrees 47 minutes and 112 degrees west longitude； is in the valley portion of the Canyon； between the mouth of Marble Canyon and a point south of Vishnu's Temple； a little west of where the Colorado River changes its course from south to southwest。 It is wholly within the greater depths of the Grand Canyon； east and southeast of the Kaibab Plateau。 The intercanyon valleys of this portion of the Grand Canyon extend back from three to seven miles west of the river； and are eroded in the crest of the Monoclinal fold that forms the eastern margin of the Kaibab Plateau。〃
There are also interesting remnants of Algonkian directly opposite El Tovar to the west of the Bright Angel Creek。 They are easily discernible by their brilliant geranium or vermilion color。 They extend for a mile or more westward； and rise above the Tonto sandstones； which properly belong above them。
The most remarkable deposit and exhibition of Algonkian strata in the Canyon； so far as known； occurs directly east of the great Kaibab Plateau； opposite the Little Colorado River。 Here there must be several； possibly five or six thousand feet of these interesting strata； which Nature has allowed to remain up to our day。 Geologists are now investigating them more thoroughly than ever before； and we may expect； when they publish the reports of their labors； that our geological knowledge of the Algonkian epoch； and possibly of other puzzling matters； will be much increased by the light they will throw upon them。
CHAPTER XIV。 The CanyonAbove And Below
The Canyon Rim。 There are several rather remarkable and surprising points of difference between the Canyon on the rim； and the Canyon in its depths。 Above； the whole Canyon region； save during the rainy season； is waterless； and while not barren； owing to the growths made possible by winters' snows and summers' rains； it is a veritable desert as far as water； whether in streams； creeks； rivulets or springs； is concerned。
Drainage of the Canyon。 On both sides of the Canyon； all the surface water of the rains drains away from the Canyon for miles； and not until it has flowed； perhaps from within a few feet of the edge of the abyss itself； from twenty to a hundred miles； does it empty into the drainage channels which； burrowing down into the earth； reconvey the water back； by circuitous routes； into the depths of the Canyon； there to add to the flow of the Colorado。
Rain at El Tovar。 Take rain that falls； for instance； at El Tovar itself； within sight of the Canyon。 After a heavy storm； the visitor may see it dashing down the Bright Angel Wash （up which the railway runs） to Bass Station； where it turns and enters the narrower section of the Wash。 It flows in a general southwesterly direction； and enters the Coconino Wash； which discharges into the open plain； once the bed of the great inland Eocene Sea。 Here it disappears。
An Underground Stream。 In this plain are some breaks in the rocky bed； which allow the water to flow down to join the underground current of the Havasu （or Cataract） Creek； which runs on the northern slope of Bill Williams Mountain。 This underground stream （as explained in the chapter on Havasu Canyon） emerges at the head of the village of the Havasupai Indians； in a thousand springs； and then flows on； over several precipices； to the lower levels； thus making the exquisite waterfalls that have rendered this Canyon world…famous。 It finally reaches the Colorado some fifteen miles away； where its clear blue waters are soon lost in the muddy flood of the 〃Red。〃
Water in the Canyon。 After one has ridden in the hot summer sun over this waterless region； and seen the waterwagons of the miners and sheep men； and the great train of water…tanks being hauled for the guests at El Tovar； it is a surprise and a wonder to find below； in the heart of this rocky…walled Canyon； a mighty river dashing its headlong way to the west。 Many a time； after a week of riding horseback on the plateau above； until every particle of moisture seemed to have evaporated from my body； have I gone down the trail to the river and camped there； enjoying a swim several times a day； and rowing up and down one of the quiet stretches； between the rapids； where boating is not only possible but reasonably safe。 In the Bright Angel and the Shinumo on the north side； and the Havasu on the south side； one may swim； or at least soak and paddle； in cooling waters； where waving willows； giant sycamores； and green cottonwoods sway above the streams； and rich verdure of great variety lines their banks。 What a wonderful contrast；above and below！
Difference between the Rim and the River。 Another remarkable difference； or surprise； is found when one leaves the rim above； where the weather is lovely and there is
