twhite That sounds entirely feasable, since the original Central Pacific route between Bowman and Colfax, though somewhat 'roundabout', avoids the heavy tunnelling of the Harriman second trackage. And the gradient isn't that bad, either, I think it's about 2% rather than the 2.2% on the original line between Rocklin and Bowman. Actually, the heaviest grades are encountered between Colfax and Emigrant Gap, where there are several stretches of 2.4% on parallel double track. After that, between Emigrant Gap and the summit at Norden, the grade eases considerably, which I've always found interesting, as that is when the line enters the true 'Mountain' country--but it only proves that Judah knew what he was doing when he laid the original CP line out as a 'ridge-top' route. That long ridge rises gradually to the Summit, instead of just jutting up suddenly. ... there is a fairly stiff 2.2% grade just east of the Chinese Wall through Summit Tunnel, but with the power available to the UP these days, that would seem like a somewhat minor problem.
That sounds entirely feasable, since the original Central Pacific route between Bowman and Colfax, though somewhat 'roundabout', avoids the heavy tunnelling of the Harriman second trackage. And the gradient isn't that bad, either, I think it's about 2% rather than the 2.2% on the original line between Rocklin and Bowman. Actually, the heaviest grades are encountered between Colfax and Emigrant Gap, where there are several stretches of 2.4% on parallel double track. After that, between Emigrant Gap and the summit at Norden, the grade eases considerably, which I've always found interesting, as that is when the line enters the true 'Mountain' country--but it only proves that Judah knew what he was doing when he laid the original CP line out as a 'ridge-top' route. That long ridge rises gradually to the Summit, instead of just jutting up suddenly.
... there is a fairly stiff 2.2% grade just east of the Chinese Wall through Summit Tunnel, but with the power available to the UP these days, that would seem like a somewhat minor problem.
Tom, with a copy of the Southern Pacific 1980 track charts covering the Donner Pass route, I have the means to confirm or refute your statements. The grades varied all over the place, so I'll give the highlights.
Between Rocklin and Foothill the eastbound track held pretty steady at 1.5%, the eastbound track was steeper such as the 2.65% grade above Penryn. While the westbound track continued at 1.5%, the westbound track had 2.12% to milepost 137
Beyond Long Ravine, east of Colfax, both tracks had a steady 2.43% grade to Emigrant Gap where the grade dropped to 1.88% until Norden. There was a short stretch of level track eastbound just west of the summit while the westbound track had a 1.88% grade. From east of the summit, eastound had a 1.47% grade while the westbound's was 2.0% From milepost 196 to Truckee the grade was 2.26%.
And just think that John Signor's book on Donner Pass said the grades didn't exceed 2.2%!
By the way, the steepest grades encountered between Roseville and Oakland via Martinez were 1.00 eastbound for the southern approach and 0.48% the the westbound approach to the Suisun Bridge between Benicia and Martinez. Some eastbound trains required a helper: I've seen photos of Consolidations pushing behind the caboose in this service.
Mark
trainfan1221 I wasn't aware BNSF used that route, I know its the old Western Pacific line but thought UP had quite a few trains there.
I wasn't aware BNSF used that route, I know its the old Western Pacific line but thought UP had quite a few trains there.
Here is a peek of a contemporary BNSF train on UP's Feather River route.
markpiercea copy of the Southern Pacific 1980 track charts
markpierceBeyond Long Ravine, east of Colfax, both tracks had a steady 2.43% grade to Emigrant Gap
markpierce John Signor's book on Donner Pass said the grades didn't exceed 2.2%
timzThose are the usual SP charts, with 5 or 10 miles to the page? If so, they tell you almost nothing about the grades-- they just claim to give the "maximum grade" and the "ruling grade", the latter being hard to define. (The former's not that easy, either)
Yes, the pages are in 5 and 10-mile segments. Nevertheless, the track charts show grade segments in lengths in smaller increments when there are grade changes. Some grade segments are in lengths much shorter than a mile, so we're not talking about averaging grades over a length of 5 or 10 miles here. Anybody out there have a better source of information on the grades than those track charts?
Mark:
You're right about that grade around Penryn--it actually seems like a little bit of a roller-coaster when you're coming down it off of Newcastle.
I've never really understood the term "Ruling Grade" as it applies here--even though Signor says that it was 2.2% average. I know that the Pacific Railroad Act specified 2.2% for the grade over the Sierra (based on the old B&O grade over the Alleghenies), but I would say that the CP just considered it to be an 'average' for their Sierra mileage not cut into stone, as it were.
Of course, Charlie Crocker also paid a geologist to tell the government that the Sierra Nevada began near what is now Roseville due to the soil composition changes on the east bank of a creek, LOL! That got the railroad additional funds for 'mountain' building and geologically eliminated the Sierra Foothills entirely.
And the Sierra doesn't rise gradually out of the Valley, it does so in a series of 'steps'--you can even notice it from parallel I-80. A big rise from around Loomis to Auburn, then some easing into Colfax, then another big rise from Colfax up to Emigrant Gap (with the heaviest grades), then a long gradual rise to the Summit. So in effect, even despite those short segments of 2.4, 2.5 and 2.6% gradients, SP was able to say that the 'average' ruling grade from Rocklin to Summit was 2.2%.
But as I said, I've never understood the term 'average ruling grade'. Tennessee Pass in Colorado is a good example: A section of 3-3.2% grade on an otherwise 1.5% stretch of track gave the Pass a ruling grade of 3%. Still trying to figure out how they arrived at that. But that's just me, I suppose.
Tom
Tom View my layout photos! http://s299.photobucket.com/albums/mm310/TWhite-014/Rio%20Grande%20Yuba%20River%20Sub One can NEVER have too many Articulateds!
Ruling Grade is sort of a holy gilded touchstone thing to the railfan community, I think because it enables simplified, precise comparisons between railways that stand independent of all the messy stuff that's hard to get information on or bring into a coherent picture, like fuel costs, labor costs, car-hire costs, etc., not unlike ERAs for baseball pitchers. In reality, ruling grade is imprecise in its definition and understood by railways to be little more than a rough guide. If someone at the railway says, for example, that the ruling grade on Route A is 1.8% and on Route B is 2.0%, that doesn't mean very much to anyone at the railway because in the whole scheme of things it's assumed there will be are many other factors at play. One territory I once dispatched had a succession of ruling grades between 1.2% and 1.8%, according to the track charts, but all that meant was a train spent a lot of time slogging up all of them, and could find novel ways to stall on any of them. Now if you're talking about two grades that are 1.0% and 2.0% -- now that's significant.
I don't know what an "average ruling grade" would be, that's a term that is paradoxical. A grade is either a ruling grade, or it isn't.
For everyday purposes, think of a "ruling grade" as the grade that determines the maximum tonnage that a locomotive (or m.u.'d diesels, with or without DPU) can haul "single," i.e., with one train crew collecting pay. That in itself implies that at maximum tonnage the locomotive will be just able to move the train (and perhaps not be able to restart it), and it implies an economic model of railroading that consists of heavy trains moving at lowest cost, and implies a known drawbar strength and train/track dynamics regime. If the economic model is based on something different, such as one that emphasizes speed and de-emphasizes cost, or if somehow the drawbar strength or train/track dyanamic regime could be changed drastically, the ruling grade on the same hill may be something quite different.
The reason railways use "ruling grade" is because maximum grade and average grade are even more useless as tools to understand the railway's vertical profile. Maximum grade is measured over some minimum distance, right? So if one happens to pluck two closely spaced points at random, and those points happen to each be on either side of a bad rail joint, you could pronounce the maximum grade as something approaching infinity. Even over the length of a half a stick of rail in a soft spot, maximum grade might be 8 or 9%. And average grade, if you spread out the points far enough, looks like 0.0%, if, say, your points were spread as far as the on-dock rail at the Ports of Los Angeles and New York/New Jersey, which doesn't tell you anything about what trains will do in between. Thus when someone says the maximum grade on such-and-such a hill is some cosmic number like 5.6%, and therefore this hill must be the toughest in North America, I just roll my eyes (and I've been to charm school so I do it without any actual eye movement now.)
For what it's worth, the "ruling grade" on Donner eastward is listed by UP as 2.65%, at least in one public document I have on hand.
Also for what it's worth, the ruling grade eastward on Tennessee Pass was defined by D&RGW as 3.0%, not 3.3%, at least by 1956 and thereafter. Having been in the cabs of many trains on that pass, I'd say that from an Operating Department perspective, Tennessee Pass really is a ruling grade of 3.0% (or something in that range), not 1.5%, because most trains were never powered enough to do better than 11-12 mph on the steep parts of the hill that the track chart claimed were 3.0%, and ran somewhat faster on the flatter parts.
RWM
I'll take what's on the track chart over any operating or mechanical wag-ing. The track chart is a schematic of the engineer's profile map with the grade profile shown without vertical curves. On longer stretches of 800-1000' + you'll find those grades will still match pretty well with what's actually on the ground today. Having been sent over and over and over again to Morley on Raton Pass to verify a 500 foot stretch of 4.03% actual grade (absolute steepest part of the hill), I'm pretty comfortable with the relative precision of what's being shown. (Damned operating bozoes and some numbnutted EMD mechanical engineers were always whining about that piece of hill...remember, track charts are a SCHEMATIC and not the detail of what's going on - track charts rob data from other engineering documents.....for what it's worth, we also had civil engineers who came up through the track department without spending any time in engineering who were also dumber than a box of rocks when trying to understand a track chart or a profile map)....surfacing will change things in a small area, but other areas in the larger scope of things tend to wash over what a surfacing gang did.
Diningcar will jump in here somewhere, but ATSF, DRGW and UP's engineering profile maps were based on top of subgrade as constructed (and then you add 18"+/- of track and ballast. If you had a change of grade, the maps were edditted to show that along with high water data, etc.....From my point of view, finding fault with the track chart is like fine tuning a watch with a jackhammer. If you want super precise numbers, go through the expense of leveling and measuring every day.
Union Pacific's PMV vehicles map their territory on rotation about every 2 years using GPS. Because it is not referenced to a HARN or VPS base station point, the vertical component of their GPS is very imprecise (the folks that run the system have a handle on this, but many others in UP are certifiably clueless....then they see elevations "jump" at junction points. -It's the nature of the GPS beast.) Within each run, the precision is good to excellent, but don't go looking at "accurate" )
I'm sure tonnage ratings were more useful to the railroader than grade percentages. In Signor's Donner Pass book there are at least two tables giving the tonnage ratings for each class of locomotive.
As an example, the October 24, 1952 chart in part shows the following ratings for AC-6-12 locos: 2,400 tons Roseville to Colfax (but only 1,450 tons on the steeper no. 1 track), 1,450 tons Colfax to Sparks, 3,650 tons Sparks to Truckee, and 1,850 tons Truckee to Summit.
twhite So in effect, even despite those short segments of 2.4, 2.5 and 2.6% gradients, SP was able to say that the 'average' ruling grade from Rocklin to Summit was 2.2%.
When Harriman added the second track below Colfax, the new double-track Tunnel 18 forced a short steep grade on the ordinarily-descending westward track; it likely averages 2.7% actual grade for a half-mile or so. Aside from that I doubt anyone can find a half-mile of track anywhere in the Sierra that averages as much as 2.3% actual.
(OTOH the grade compensated for curvature at the usual 0.04% per degree averages around 2.35% for the steepest six miles.)
Mud, I agree with you on the quality of UP, D&RGW, and Santa Fe track charts. SP's on the other hand? Well, they are a start ...
I was unknowingly spoiled growing up on UP and D&RGW track charts, and naively assumed all Class 1s adhered to that standard of care. Boy was I wrong! The next Class 1 I went to had little more than sketches drawn with a dull pencil, and they were 40 years out of date.
mudchicken The track chart is a schematic of the engineer's profile map with the grade profile shown without vertical curves.
markpierceI'm sure tonnage ratings were more useful to the railroader than grade percentages. In Signor's Donner Pass book there are at least two tables giving the tonnage ratings for each class of locomotive. As an example, the October 24, 1952 chart in part shows the following ratings for AC-6-12 locos: 2,400 tons Roseville to Colfax (but only 1,450 tons on the steeper no. 1 track), 1,450 tons Colfax to Sparks, 3,650 tons Sparks to Truckee, and 1,850 tons Truckee to Summit. Mark
Seriously, we ignored those when I was last in the operating department. We used experience of the day before, and the week before, and the month before, and the year before, as our guide to dispatching locomotives. Often the tonnage charts were just plain WRONG. SP's listed some "ratings" at various times that were demonstrably laughable. Timz will perhaps recall.
Actual laughable ratings are fairly rare-- SP used to rate SD45s at 1650 tons eastward over Donner, which sounds unlikely, but since everyone knew better than to send a 6600-ton train up there with four SD45s no one can say for sure it was hopeless. But RWM is remembering the SP's 1960s ratings eastward out of El Paso, which did look hopeless all right.
Try this for a current example (at least I think it's still current):
The ruling grade westward on the Overland Route, Chicago to Truckee, is the climb from Montello to Valley Pass; it seems the sustained grade there is unlikely to be less than 1.31% compensated (details below). By UP's tonnage ratings three AC44s on a grain train would be allowed 14738 trailing tons, requiring something over 140000 lb TE from each unit-- okay, maybe they can manage that. But three DC SD70s are alleged to be good for 12667 tons, demanding around 124000 lb from each unit-- think there's any chance of that? As always the GP60 rating is the least likely, 3248 tons (95000 lb TE per unit).
You'll end up with the elevation data for the benchmark at the east end of the Long Ravine bridge, and for another benchmark near the Blue Canon road crossing. It says the former is about 2 ft below the track and the latter is about 6 ft above the track; difference in elevation between the two benchmarks is 2284.6 ft (which is supposed to be correct within a tenth)-- so the track climbs about 2277 ft in that distance.
In what distance? There's the rub-- I happen to know the horizontal distance along the eastward track is 115470 ft, correct to... hopefully better than 50 ft, probably better than 100 ft, but you'll have a hard time confirming that.
(Those who are paying close attention will notice that the topo map shows the Long Ravine benchmark as elevation 2402 and the Blue Canon as 4686. When the maps were drawn, "sea level" was assumed to be a bit higher than it is now assumed to be.)
(Those who are paying even closer attention will say I should have used dynamic height instead of orthometric. You're probably right.)
timz:
I think that the Central Pacific figured their original elevations from the starting point in Sacramento, which is about 75 feet above mean sea level. According to the CP, then the Sierra actually started at the 'geologic' beginning of the mountains, on the east bank of the creek that cuts through present Roseville, which is about 125 feet elevation. It's still pretty confusing.
'Mean' sea level, of course, would be the trackage at San Francisco Bay in--say--Oakland, however the CP did not extend west to Oakland for several years after original construction. So there's a possibility that elevations were considered from the 'base' point in Sacramento for a long time.
And one has to also consider the elevation factor within the width of the mountain range. Though the Sierra are a long mountain range--well over 300 miles from north to south, they are also a very NARROW mountain range, a geologic raised 'fault-block' that rises steeply from west to east. The aerial distance from Roseville to Reno is perhaps about 80 miles--I can even drive it on I-80 in less than 120 minutes on a good traffic day--but the elvation difference is almost 7000 feet from Roseville to the crest. That's an awfully short distance to work in a railroad that can get from point A to point B with reasonable grades, LOL!
Which is DEFINITELY why WP decided on a more circular, northerly, easier graded route up through the Feather River Canyon when it was built in the early years of the 20th Century. It was the only other practical central route through the mountains. However, being a canyon floor route, relegated to a maximum 1% grade, it could only be single-tracked in its location, and the extreme curveature of the canyon has always pretty much negated speeds of much over 25mph.
I think UP has realized this now, with traffic in the largely single-track Feather River canyon approaching stagnation, with the addition of an increased BNSF northwest traffic pattern between Stockton and Keddie, and the wisest thing for UP to do is to do whatever it can to increase traffic on Donner.
Actually, UP's east-west traffic between Oakland and Chicago is NOT necessarily all double-stackers. There is still a great deal of 'other' freight traffic that can negotiate Donner Pass tunnels with ease, and UP has tended to use Donner for this other traffic, especially a slowly growing perishable west-east traffic from the Sacrameno, San Joaquin and Salinas Valleys. It's a slow grow from trucks, but it seems to be working relatively well for UP during the 'perishable' season that now lasts from Spring to early Fall. I'd be surprised that UP re-captures the incredible volume that SP put over Donner Pass in the 'glory' years, but it seems to be a start.
I think, despite the grades, that Donner will prove to UP (finally!) that it's still the most viable east-west route out of Northern California. That original Judah ridge-top route still has a lot of merit.
But I think that the Canyon, from Keddie east, still deserves to be kept open as an 'alternate'.
I doubt that UP's decision making process regarding upgrading western routes is driven by much consideration of what the BNSF might do. As somebody noted a few pages back -- and it can be confirmed by reference to BNSF's system maps on their website -- BNSF has track rights on both the Feather River and Donner Pass routes as far east as Salt Lake. In fact, since they also have rights on the D&RG's route from Salt Lake to Denver, a central routing exists for the BNSF should they choose to use it.
,
timz Anyone who still "believes" the chart can get part way to enlightenment by going to www.ngs.noaa.gov/cgi-bin/ds_pid.prl and typing ks0349 and ks0389 into the box. Click "Submit", then "Select All", then "Get Datasheets". You'll end up with the elevation data for the benchmark at the east end of the Long Ravine bridge, and for another benchmark near the Blue Canon road crossing. It says the former is about 2 ft below the track and the latter is about 6 ft above the track; difference in elevation between the two benchmarks is 2284.6 ft (which is supposed to be correct within a tenth)-- so the track climbs about 2277 ft in that distance. In what distance? There's the rub-- I happen to know the horizontal distance along the eastward track is 115470 ft, correct to... hopefully better than 50 ft, probably better than 100 ft, but you'll have a hard time confirming that. (Those who are paying close attention will notice that the topo map shows the Long Ravine benchmark as elevation 2402 and the Blue Canon as 4686. When the maps were drawn, "sea level" was assumed to be a bit higher than it is now assumed to be.) (Those who are paying even closer attention will say I should have used dynamic height instead of orthometric. You're probably right.)
The above reminded me of the following essay - are any of you familiar with it;
Selected railroad reading: Numbers Trains, July 1982 page 44 accuracy beyond the decimal point ( COMMENTARY, "LEMASSENA, ROBERT A.", TRN )
If you are, 'nuff said; if not, be advised that it is dead 'on point'. It even starts out with the whole debate over what elevation some D and RG pass is - Cumbres or Marshall, I can't remember which - according to the various 'authorities'.
If there's some interest, I might see what I can do to get it posted or on-line one way or another . . .
- Paul North.
timz twhite there is a fairly stiff 2.2% grade just east of the Chinese Wall through Summit TunnelWhere did you read that? As I recall the special instructions say westward trains that can't make 14 mph on the climb to Donner are not supposed to enter the formerly-eastward summit tunnel, which is 1.96 miles of constant 1.47%. Would there be any need for such a rule for westward trains via the old line? Maybe not, in which case the tonnage rating on the old line would likely be no lower than at present. (Might be higher.) By the way: looks like SP removed 7.0 miles of track above Emigrant Gap and 6.7 miles over the summit.
twhite there is a fairly stiff 2.2% grade just east of the Chinese Wall through Summit Tunnel
As I recall the special instructions say westward trains that can't make 14 mph on the climb to Donner are not supposed to enter the formerly-eastward summit tunnel, which is 1.96 miles of constant 1.47%. Would there be any need for such a rule for westward trains via the old line? Maybe not, in which case the tonnage rating on the old line would likely be no lower than at present. (Might be higher.)
By the way: looks like SP removed 7.0 miles of track above Emigrant Gap and 6.7 miles over the summit.
Timz:
Sorry for the confusion--I was talking about the original Summit Tunnel of 1867, not the newer 1.96 mile tunnel when I mentioned the gradient. The 'Chinese Wall' is on the original (now out of service) line over the Summit itself. Before it was put out of service by SP, it was the westbound track between Truckee and Norden, and SP considered that short stretch of track to be a kind of operational nightmare. And when SP began diverting traffic from the Overland to its own Sunset Route (so it could ship east on its own rails instead of turning traffic over to UP at Ogden) back in the late 1960's, the traffic decline on the Donner Pass route gave the railroad the excuse to abandon the original Pass in favor of bi-directional traffic through the newer tunnel on a much easier gradient.
Fascinating discussion.
Please help out a guy from Indiana...what exactly do you mean by "ridge top route". It has been referred to many times.
ed
twhite there is a fairly stiff 2.2% grade just east of the Chinese Wall through [the original 1867-or-whenever] Summit Tunnel
Paul_D_North_JrSelected railroad reading: Numbers Trains, July 1982 page 44 accuracy beyond the decimal point ( COMMENTARY, "LEMASSENA, ROBERT A.", TRN )
timz twhite there is a fairly stiff 2.2% grade just east of the Chinese Wall through [the original 1867-or-whenever] Summit Tunnel Where did you read that?
Didn't have to 'read' that anywhere. I grew up there and have walked the abandoned old summit line quite a few times.
With a transit? The 2.2% extends from where to where?
No, with my feet. The 2.2% extends from the middle of old Summit Tunnel down past the Chinese wall and about 1000 feet or so into the concrete snowshed that wraps around Donner Peak. It's brief, but nasty, according to westbound engineers when the old line was in use. Which has always kinda/sorta surprised me since that section of the Pass was built downward, west to east. The rest of the grade down is quite a bit gentler.
MP 173,
SP's Donner Pass route is unique, to my incomplete knowledge, in North America in that it is a ridge top route.
A typical rail crossing of a mountain range follows the river and stream valleys for as long as possible as mother nature thus has done most of the excavation. On the final climb to the summit the line may climb above the by now typically small stream, but the line is typically well down the slope. Perhaps the most extreme case of this is the SP&S and UP in the Columbia River Gorge between Vancouver/Portland and The Dalles Oregon, where each line crosses the summit of the Cascade Range at an elevation of less than 100 feet. The GN, NP summits of the Cascades are both over 2800 feet and require tunnels to do it.
The Sierra Nevada is different from most mountain ranges in that it is one big rotated block of crust. The West side of the block is rotated down and is far below the later fill that makes up the Central Valley. The East side is bounded by one or more faults. The SP passes the east side fault somewhere around Truckee. The rotation happened many millions of years ago, so glaciers and running water have had lots of time to sculpt the block. The result is that if you start up the rivers by the time you get 50 or 60 miles in you are in a 2000 foot deep canyon that you can not climb out of at a reasonable grade for a railroad.
Theodore Judah's solution was to get on top of the ridge, near Rocklin, and stay close to the ridge top as he headed East. If you drive I-80 you will note it does the same thing, though not as consistently since they could use 6% grades vs. 2.2% mandated by congress for the UP/CP. If you are still not convinced, take CA 49 either North or South and you will drop into either the Yuba or American River valleys, and drop is the operative word.
Cape Horn, where passenger trains stopped to let the tourists view the "awful gorge" is in the American River drainage. At Yuba Gap the railroad crosses over the ridge top from the American River to the Yuba River, hence the name.
Mac McCulloch
to a thorough and well-done explanation by Mac [above].
The dominant principle is to get past the mountain range at the lowest practicable elevation, to minimize the lifting effort required by the locomotives, and hence time and costs. That usually leads to a tunnel under the summit to pre-empt having to lift the trains the last several hundred feet [sometimes thousands of feet], which tunnel - since the mountains slope outwards down to their lower slopes - is then usually made as long as is practical for the situation and finances of the line. Once the summit tunnel's site is selected, the locating engineer's challenge is then to get the line to the tunnel with reasonable grades. Most often, the tunnel and lines are well down in the valleys, as Mac describes, as long as a tunnel there will be of acceptable length.
The difference with the CP's line is that with the primitive tunnel drilling methods of the day, the summit tunnel just could not be very long - hence it had to be pretty high up. In the Donner Pass topographic situation, that meant the tunnel was going to be well above the stream's valleys anyway, and above many of the approach ridges as well. Faced with that dilemma, there was no longer a reason to avoid the ridges, because using the ridges would not be an unnecessary elevation climb. Instead, the ridges became just another terrain feature that the CP's builders could use to best advantage - and were, in this rare instance.
Another significant portion of a major line that is on top of a 'ridge' is the original east slope to UP's Sherman Pass. I forget the exact words that Gen. Grenville Dodge used to describe the 'plane' or 'incline' that he discovered that day long ago while he was being chased by hostile Indians, but it is clear that's what he meant. The prevailing terrain there is far more gentle than at Donner Pass, and so the 'ridge' is not quite so obvious or dramatic as Mac describes above, but that's what was done.
Other than these 2, I can't think of any others quickly. Maybe in the vicinity of Bluefield yard on the former N and W [now NS], but I'm not real familiar with that area.
Mac nailed the Donner Pass route to a "T". Judah made several surveys into the Sierra looking for a practicable route--several of them following river canyons. And as Mac says, the river canyons rise very steeply, especially at their upper elevations--way too steep for a railroad to climb out of with any kind of practicable grades. Both the American River and Yuba River watersheds were considered and discarded as canyon-bottom routes because of these features.
One other thing about the Sierra Nevada--it is a raised and tilted fault-block, but the elevations become higher and higher the further south you travel the range. So high peaks in the north-central Donner area may rise to about 8-9000 feet, while further south, the peaks can average between 10,000 and 14,000 feet. It's a narrow mountain range in width, but an extremely tough one to traverse, especially since it falls off very sharply to the east once you surmount the summits.
The Feather River drainage is far to the north, where the elevations in the Sierra are not as great (about 5000' at the watershed divide), which explains the more 'circular' route of the original WP route in the canyon. But even then, the WP had to construct a long tunnel at Spring Garden to go from the feeder creeks of the North Fork of the Feather to the Middle Fork and continue its route east. If you look at maps of the two railroads beginning from a common point of, say, Sacramento, you'll see that the Feather River route jogs almost due north in a long, roundabout arc, while the Donner Pass route takes an almost straight shot (within geographic reason, of course) east up the ridges.
Yes, much stiffer grades than the more gentle Feather River route, but much more direct.
But Mac's right--it's the only ridge-top route I can think of at least out here in the west.
Mac:Great answer...it helps, but I am not exactly 100 on line. When you say the mountain rotated downward, are you saying it literally toppled over, or something like that? What the heck would have caused that?
The nature of the Sierra Nevada makes it obvious why WP took the route they did.
Regarding the quote from General Dodge..."If we save our scalps I believe we have found a railroad line over the mountains."
MP173Great answer...it helps, but I am not exactly 100 on line. When you say the mountain rotated downward, are you saying it literally toppled over, or something like that? What the heck would have caused that?
The block of crust that forms the mountains was lifted on its eastern side by some geological force, causing the western side to sink. (think of a piece of board floating in water. If you lift up at one edge the other side sinks deeper into the water.)
MP 173
The entire Sierra Nevada range is a huge block of crust probably about 150 miles across, east to west. The entire block rotated, west edge down, east edge up. That made the top of the range the top of the east edge of the block. Erosion has moved the actual summit a few miles to the west and stripped off all the soft rock from the eastern portion of the block leaving the underlying granite exposed at the modern summit and for miles on each side as the railroad traverses it.
This rotational process took a long time, probably millions of years. As to cause, we are into plate techtonics beyond my knowledge and ability to describe. All of Nevada, and Utah to the Wasatch front is known as the "Basin and Range", and the same pattern is repeated several times, but on a smaller scale. If you google "basin and range province" you can find out more than you ever wanted to know about the geography and geology. The Wasatch Mountains were created by another major fault with the upthrust to the West.
Mac
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