Grand Canyon 3-D Tour
About 1.25 miles
North-Northeast of Pearce Ferry
A chronology of transitions from:
Near River Mile 280
Pearce Ferry Rapid
1) Lake Mead
2) To a new superimposed path for the Colorado River
3) Which became a “riffle” near the old Pearce Ferry take-out.
4) This “riffle” became a moderately severe rapid in late 2007.
5) The combination of silt deposited by the river along with
highly variable water levels in Lake Mead will continue to produce
rapid changes in years to come.
1985, 2010, 2014, and 2017
The photographs shown above and below were posted on NASA’s Earth
Observatory page on Sept. 22, 2010. http://earthobservatory.nasa.gov/IOTD/view.php?id=45945
Both photographs show:
1) The extreme western end of the Grand Canyon (lower right edge)
2) Pearce Bay (To the right and slightly below the center of the
3) Wheeler Ridge (Above and to the right of the center of the
4) Iceberg Canyon (Upper left quadrant)
5) Gregg Basin and Sandy Point (Lower left quadrant)
However, the top photo was taken Aug. 22, 1985 while the bottom
photo was taken Aug. 11, 2010.
In the 25 year interval from 1985 to 2010, the
Colorado River deposited many hundreds of millions of tons of silt
into the former upper end of Lake Mead. Water levels in Lake Mead
have been dropping since 1998. The narration below describes the
The picture above is via NASA’s Earth Observatory and
shows the status of the lower end of the river as of July 21,
2014. Lake Mead is currently at its lowest level since it was
being filled in the 1930s. The Colorado River’s delta has now
reached the north shore of Sandy Point.
The picture above is a Google Earth view as of June
2017. The Colorado River's delta has filled in most of the area to
the north of Sandy Point. The delta will inexorably continue to
build southward out into Lake Mead; but once past the tip of Sandy
Point, progress will be slower since the lake is much wider.
Construction of Hoover Dam (Boulder Dam) began in
1931 and was completed in 1935 as part of a project to “reclaim
the desert for productive human usage”. (Hence the name “Bureau of
Reclamation”.) By early 1941, the Colorado River had filled the
reservoir to capacity to form Lake Mead.
The historic photograph below was taken July 12,
1950, and shows what the upper end of Lake Mead looked like before
large amounts of sediment had accumulated. (Estimated water level
is 1176 feet.) This and other historic photographs of the area can
be found at the USGS Earth Explorer web site at http://earthexplorer.usgs.gov/
(For the photo below, use the map to zoom in (and click ) on what
used to be the east end of Lake Mead, pick a date prior to 1955,
click on “Data Sets”, expand “Aerial Imagery”, check “Aerial
Photos Single Frames”, and click on “Results”.)
The silt-laden Colorado River exits from the Grand
Canyon (lower right quadrant) into Lake Mead. Pearce Bay is in the
lower left portion of the lake, and what will become the location
for Superimposition Rapid is just to the right of the two points
of land that stick out into the lake just to the north of Pearce
Bay. If you look just to the right of the northernmost of the two
points, you can see a small island. There is a submerged ridge
that connects this island with the higher ground to the left, and
after another 50+ years of changes to Lake Mead, the river will
hang up on this old ridge to produce Superimposition Rapid.
Before Glen Canyon Dam was built, the silt load of
the Colorado River (as measured near Phantom Ranch in the Grand
Canyon) averaged 3 to 5 tons per second. (Different sources give
different amounts) Before Hoover Dam was built, this sediment
ended up in the Colorado River’s delta, but after it was built, it
was all deposited in Lake Mead.
The topographic map above from http://www.topozone.com
shows the old ridge that the river is now crossing. (The old ridge
is the narrow peninsula that sticks out into the lake just below
the BM 1250 label.) The lowest lake shoreline shows that the top
of the old ridge was exposed above the 1157-foot level. (The
estimate date for the low-lake contours is about mid 1972.) Also
the 1160-foot contour line is shown on the ridge which increases
the pre-erosion level of the old ridge to above the 1160-foot
The small island that could be seen in the previous
1950 photo shows up as the small hill (closed 1200-foot contour)
at the end of the peninsula. The Pearce Ferry take-out is off the
bottom edge of the map to the left of center.
An April 15, 1962 photograph at http://www6.nau.edu/library/scadb/imagedisplay.cfm?item_num=9383&type=Image
also shows this old ridge exposed above an estimated Lake Mead
water level of 1157 feet. (View looks south with the peninsula
just above the lower edge.)
The picture above shows the location for the
incipient rapid as it appeared in September 1992. (Estimated Lake
Mead elevation is 1174 feet.) The upper end of Lake Mead has
filled with silt. Pearce Bay is in the lower left hand corner. The
two points of land in the upper left corner are the same as shown
in the earlier pictures. What was an island in the first picture
and the end of the peninsula in the topo map, is now the small
triangular light area just to the right of the river. This area
will be submerged again during the high water levels seen in the
late 1990s (see graph below), but the final path of the river will
be near what can be seen in this photograph.
Vertical view of what used to be the northeast end of
Lake Mead. (Estimated date for the photograph is April 8, 2004.
Estimated Lake Mead elevation is 1140 feet.) The (historic)
take-out at Pearce Ferry (at the lower end of Pearce Wash) is in
the lower left quadrant - near River Mile 280 in the standard
Grand Canyon river guide books. “Superimposition Rapid” has
subsequently formed where the two ridges closely approach the
river - midway between the pin and the left edge. The pin marks
the estimated location of the 1923 photograph shown at the bottom
of this page.
Before Hoover (Boulder) Dam was built, the Colorado
River exited from the Grand Canyon (off the right edge of the
picture) and flowed left and up across what are now the mudflats
in the picture, to exit off the top edge (left of center). After
Hoover Dam was completed, the reservoir backed up to cover the
dark brown area in the picture with water. What was part of Lake
Mead as seen in the first photograph has now been transformed into
the dark brown mud flats.
Over a period of several decades, silt brought down
by the Colorado River filled in the old river channel and spread
out to cover an area more than a mile wide to form a broad silt
flat. The bottom of the old river channel is some 300 feet down
under the silt. (A graph at http://www.durangobill.com/GCriverProfile.html
shows the river elevations for both before and after Hoover
The graph above shows the water level in Lake Mead
starting with 1980. The plotted levels into 2019 are forecasts via
the U. S. Bureau of Reclamation as of the June, 2017 USBR report http://www.usbr.gov/lc/riverops.html
Historical water levels can be seen at http://www.usbr.gov/lc/region/g4000/hourly/mead-elv.html
The water level in Lake Mead reached its maximum
elevation in 1983. When the lake level subsequently receded from
this maximum elevation, the river had no guide as to the location
of the old channel, and established a new path across the silt
flats, approximately in its current position. Most of this new
path area was periodically exposed and resubmerged over the next
20 years, but the drought that has set in during the early 2000s
has severely lowered Lake Mead. As the water level lowered, the
river became entrenched in its new path.
Please see “Transition to a more arid Southwest” (and
related technical paper links) at http://www.ldeo.columbia.edu/res/div/ocp/drought/science.shtml
for the reasons why drought conditions are developing. (And be
sure to give the authors an A+ for recognizing the current problem
The geological sequence of burying an old landscape
under silt/sediment and then establishing a new river drainage
system across the top of these sediments is a process called
superimposition. In a normal geologic time frame, this requires
many millions of years. Here, at the upper end of Lake Mead, a
man-made version of the process has taken only a few decades.
In a normal geologic sequence, a new superimposed
river system might end up over the top of an ancient mountain
range. If subsequent erosion removes the softer sediments, it’s
quite possible the superimposed river might remain stuck in its
path and erode its way down through the old mountain range to form
Here, in the remnant of the upper end of Lake Mead,
the silt deposits buried an old ridge. When the Colorado River
established its new course after the 1983 maximum elevation of
Lake Mead, the river happened to end up over the top of an old
ridge. When the water level in Lake Mead subsequently dropped,
sediments on the downstream side of the ridge eroded away.
However, the ridge resisted erosion. The river thus formed a rapid
where it dropped from the relatively higher elevation of the ridge
to the relatively lower elevation downstream. It seems appropriate
to name the rapid “Superimposition Rapid”. (Alternately, if the
rapid were named for its geographical location, it might be named
Pearce Ferry Rapid or Pierce Ferry Rapid.)
The picture above shows what the landscape at
“Superimposition Rapid” looked like before Lake Mead dropped low
enough for the rapid to form. The Colorado River is entrenched in
a path that forces it to cross an old ridge. The area where
the river crosses the ridge can also be seen in the first Google
Earth picture - midway between the pin and the left edge. In both
views the river enters from the right and then flows toward the
top of the picture.
The Google Earth satellite picture (above) was
probably taken on April 8, 2004 and covers approximately the same
area as the Vishnu Temple Press photo below. With a little work
you can find the exact spot where the Vishnu picture was taken.
The white sand in the foreground of the Vishnu picture will match
the lower right end of the white sand patches in the Google Earth
picture. (On the left side of the river, above and slightly to the
right of the center copyright labels.)
The photograph above is similar to the Google Earth
picture and was taken on March 22, 2003. It was originally posted
on the Vishnu Temple Press website (Good source for rafting guide
books.), and while it is no longer posted there, you can see the
original web page at: http://web.archive.org/web/20031208154023/www.vishnutemplepress.com/pearceferry.html
The photograph above was taken by Tom Martin at
nearly the same location as the Vishnu Temple Press photograph -
but in Feb. 2008. It is inserted here (a jump in the time
sequence) to show what has happened in the 5 year period from 2003
to 2008. Notice how the river has dug down through the sediments.
(For example, the ridge a couple of hundred yards downstream in
the upper left is now part of the skyline as the photographic
location is now 20 to 30 feet lower.)
As the elevation of Lake Mead dropped due to the
drought, the Colorado River had an easy chance to erode the silt
deposits that were deposited before the drought lowered the water
level. The exception is the ridge. When Lake Mead dropped below
the 1120-foot level in 2007, the river could erode the silt
sediments downstream from the ridge, but the ridge acted as a dam
and protected the sediments above the ridge. The ridge itself
became the crest of the new rapid. (This is the upstream portion
of the rapid which is a couple of hundred feet upstream from the
large rock that subsequently emerged.)
The two pictures below are from an aerial U.S. Bureau
of Reclamation photograph that can be seen at http://www.usbr.gov/lc/region/g5000/photolab/gallery_detail.cfm?PICIDTYPE=13209
This first picture looks east across the (historic)
easternmost end of Lake Mead. In the distance, the Colorado River
exits from the Grand Canyon, flows westward (toward the
foreground) across the silt flats, and then turns north to flow
off the left edge of the picture. The old Pearce Ferry takeout is
well off the lower right edge while the location for the new rapid
is in the lower left corner.
The picture above is an enlargement of the lower left
corner of the previous picture. Both views show what the incipient
rapid looked like on Feb. 2, 2006 - Lake Mead elevation about 1140
Standing waves from a submerged pour-over rock (part
of the old ridge) can be seen.
As of late July 2007, the surface elevation of Lake
Mead had dropped about 29 feet from where it was in Feb 2006. The
soft sediments that were deposited by the river over the last 6
decades can be easily eroded. This leaves two major possibilities.
1) If the rock in the old ridge can resist further erosion, then a
severe rapid will form on the downstream (left) side of the old
ridge. 2) The river just might be able to erode down through the
old ridge. If it can erode downward, there will still be a rapid,
but the drop-off will be less, and hence the rapid will be less
The photograph at the
right was taken by “bobkerry44” on Oct. 7, 2006 and is a copy of
the original which is posted in the photos section at the gcpba
Yahoo Group. The photograph was taken from near the right bank of
the river and looks northwestward across the river to the same
portion of the ridge that appears on the left side in the Vishnu
The Vishnu picture was taken in March 2003 with the water level in
Lake Mead at about 1154 feet. By Oct 7, 2006 the lake had dropped
to about 1126 feet. The river had already taken advantage of this
height difference to erode downward toward the old ridge. The
pour-over rock that is in the center of the photograph is part of
the top of the old ridge. As the lake continues to drop in the
future, the river will become increasingly hung up on the old
ridge and the rapid will gradually become more severe.
The following 3 pictures were taken from “North
Point” (the left ridge in the Vishnu picture) and look southeast
to south over the rapid. The sequence is a record of what was
happening in the fall and winter of 2007/2008.
The first picture was taken on Sept. 1, 2007 by
Duwain Whitis (“Guide to the Colorado River in the Grand Canyon”
by Tom Martin and Duwain Whitis)
This next photograph was taken on Oct. 8, 2007 by Tom
Martin (River Runners For Wilderness) and coauthor of the above
Finally, the third picture (below) was by Tom Martin
in Feb. 2008.
Two items of interest are of note. The most obvious
is the large rock in the middle of the river. Also there is a
smaller riffle about 200 feet upstream from the rock.
Update as of June 30, 2009
The photograph above was taken by David Witton and
shows the status of the rapid as of June 1, 2009. The photo was
taken from the left (west) bank of the river and looks slightly
west of due north. The tilted strata in Wheeler Ridge can be seen
in the distance.
The top of the ridge on the left side of the photo
was the viewpoint for the previous pictures. This view looks
downstream over the rapid. The lower part of the ridge reveals
horizontal layers of loosely consolidated silt and gravel that
were deposited some 5 to 15 million years ago. These rock layers
are not cemented together as solidly as the much older rocks that
are exposed in the Grand Canyon. Thus the river has been able to
erode down through them fairly rapidly.
As the river erodes down through these more easily
eroded layers, the original submerged rock (which apparently is a
patch of conglomerate) has gone through the following stages.
1) The rock was initially submerged and just produced waves in the
2) The river began to carve out channels around the rock (mostly
to the left/west). As the river carved the lower channels the rock
emerged above the surface.
3) Further down-cutting by the river has allowed a ledge to be
exposed to the left (west) of the rock. There is also another
submerged rock that shows up near the left edge of the photo.
Update as of March 5, 2010
The picture above was taken by Tom Martin about March 2,
2010, and can be seen in the Gallery of pictures at the River
Runners for Wilderness website. http://www.rrfw.org/gallery/
The view is taken from “North Point” bluff, and looks
southeast across the rapid. The river continues to cut down
several feet per year through poorly consolidated, 5 to 15 million
year old rock. In the process, patches of somewhat harder
conglomerate rock are becoming more exposed as the river erodes a
deeper channel around them.
A ledge extending westward (from left to right in the
photo) from the original submerged rock is now fully exposed. The
river flow indicates that a further extension of this ledge is
just under the surface. The river forms foaming holes after it
pours over the ledge.
There appear to be other submerged ledges just
underwater extending out from the base of the bluff in the
These ledges may make things difficult for rafters in
the not too distant future. Where the river pours over a ledge, it
will form a “hole” with a strong breaking wave on the downstream
side of the hole. This type of water flow can easily flip a
Also, the river may end up taking a very sharp,
turbulent right turn (as you look downstream) in between these
Update as of Sept. 22, 2010
The two photographs below were taken on Sept. 17,
2010. If you click on either photograph you can see a large
version of each.
The photograph above looks southeast from “North Ridge” and shows
the east side of the rapid – right side as you are looking
The photograph above looks south-southeast from “North Ridge” and
shows the west side of the rapid – left side as you are looking
What was originally just a rock in the middle of the
river is gradually revealing itself as a ledge that extends across
the entire river. As the river erodes downward, the exposed
portion of the ledge is steadily extending westward. (Toward the
left side of the river as you are looking downstream.)
If you click on either photograph, you will get a
large version that shows more detail. The rock ledge has
interleaved layers of silt and conglomerate cobbles that were
deposited some 10 to 15 million years ago. Rocks and cobbles in
the conglomerate layers were washed in by local flash floods. Silt
layers (without imbedded rocks) were deposited by mud settling out
of a shallow lake.
The layers that can be seen in the ledge were
subsequently buried by another ~1,800 feet of sediments in
what was a closed basin up until about 5.4 million years ago.
(The old level top of these sediments is still present at the dirt
airstrip about 4 miles southwest of the rapid – see bottom edge of
the NASA photos at top of page.) Finally, the Colorado River
relocated to its present course about 5.4 million years ago, and
has been busy excavating the whole works (including cutting the
Grand Canyon) ever since.
Update as of April 24, 2011
The two photos below were taken on April 23, 2011 by Steve
The picture above looks upstream to include the east
side of the rapid. The channel on the east side of the rapid was
navigable a couple of years ago, but it’s now just a small
waterfall that bounces off a couple of ledges.
The picture above shows the main part of the rapid -
which flows to the west side of the large rock. This portion of
the river has also eroded down to a series of ledges. There
doesn’t appear to be any navigable route other than bouncing off a
ledge or two followed by a plunge into the deepening “hole”.
Update as of May 27, 2016
The PrintScreen picture above is from a March 4, 2016
video by Russell Dudley that can be seen at https://www.youtube.com/watch?v=wJ1W1kZIMQ8
. The view looks northward (downstream) from the west (left) bank
of the river.
There appears to be at least 10 feet of downward
erosion since the rapid started to form some 9 years ago.
Update as of July 26, 2017
The picture above is a Print Screen image from a
video by Tom Martin as uploaded to YouTube. https://www.youtube.com/watch?v=5IsoIJ_UqvU
It shows what the rapid looked like as of Feb. 26, 2017.
In the last year, the river has cut down several feet
just to the west of what used to be the large rock that split the
river’s flow. The result is that the entire river is now squeezed
into a narrow slot estimated at 40 feet wide. Given the turbulence
and sand load of the river, continued rapid down cutting is
likely, along with some erosion back upstream.
The rapid will probably not be runnable by rafters until
either 1) the water level in Lake Mead rises enough to submerge
the rapid (not likely for at least the next 2 years), or 2) the
river can erode upstream to where it is clear of the silt buried
If we look still further out into the future over the
next couple of decades, Superimposition Rapid will just be a
temporary phenomenon. Even with Glen Canyon Dam blocking the silt
flow that used to come down the Colorado River, there is still an
inflow of silt from the Paria, the Little Colorado, and smaller
tributaries. This silt will continue to accumulate in what used to
be the upper end of Lake Mead. The exact details of where and when
this new silt will settle out will vary with the water level in
Lake Mead, but the new silt will eventually bury everything that
is visible today. This will include Superimposition Rapid, which
will eventually be buried - never to reappear again.
The photo above was taken by Andy Pernick of the U.
S. Bureau of Reclamation on April 25, 1997.
The view looks NNE up Iceberg Canyon when Lake Mead
was nearly full (water level 1200 feet), and before silt filled
Iceberg Canyon. The site of the uppermost Iceberg Reef
Rapid/Iceberg Rapid (Devils Cove Rapid - the “Wave” of 2008) is
about “one island length” to the right of the elongated island
that can be seen near the left edge of the photo. What appears as
an island in this photo is the white colored point to the left of
the incipient Devils Cove Rapid in the next photo.
The sediment that is brought down by the Colorado
River continues to build a delta out into Lake Mead. This sediment
has buried the old river channel under some 300 feet of mud/silt.
As the water level in Lake Mead drops lower, the river establishes
new channels across these silt flats. Since the river has no
guidance as to the location of the old channel, the new channels
meander randomly across the silt flats - and in the process these
new channels occasionally end up relocating over the top of old
buried ridges. Then, as the water level in Lake Mead drops, the
river hangs up on the hard rock of the old ridges and “pour-over”
rapids develop on the downstream side.
The original copy of the above photo was taken by
Andy Pernick of the U. S. Bureau of Reclamation on Jan. 8, 2009.
The original picture (which includes better detail) can be
The view looks toward the NNE up Iceberg Canyon. The
original river channel hugged the cliffs on the right (east) side
of Iceberg Canyon. However, the river has formed a new course as
indicated by the blue dots. Areas where the new course of the
river crosses over buried ridges are indicated by paired dots. The
dots represent the estimated path of the river as of July 1, 2009.
(Also see topo maps and photo below.) The river’s course is
subject to change with no advance notice - which should be borne
in mind by anyone running the river.
These two topo maps (above and below) show the same
area as the aerial photograph except the estimated course of the
river is shown by red dots. (Red dots show up better than blue
The most northerly of the paired dots is Devils Cove
Rapid - otherwise known as “The 2008 Wave” which surfaced during
the summer of 2008. At that time, the upper end of Lake Mead was
just a short distance to the southeast. During the winter of
2008/2009 the water level in Lake Mead rose several feet and
submerged the wave - as shown in the Jan. 8, 2009 photo.
By the time the lake level dropped again in 2009,
additional layers of silt had been deposited. The delta now
extended an additional mile beyond the 2008 position and the river
developed still another new course.
A second rapid (Burro Spring Rapid) formed about 0.6
miles SSW of Devils Cove Rapid where the new course of the river
crossed another old buried ridge. This location is shown by the
second set of double dots in the above photo and topo maps. The
possibility exists that a third rapid may develop still further
downstream where the river makes a close approach to another ridge
in the lower left corner of the above photo.
The photo to the right was taken by Tom Martin about
July 1, 2009. Tom took additional photos of the rapids in this
area, and these can be seen at: http://www.rrfw.org/gallery/index.php
The view looks SSW over
the new rapids with the south end of Iceberg Canyon in the extreme
lower right corner. The persistently shrinking Lake Mead can be
seen in the upper left quadrant with Sandy Point sticking out into
the lake from the left (east) shore line.
The uppermost of the two new rapids (Devils Cove
Rapid) is in the lower right portion of the photo just above the
green vegetation patches that bracket the river, and just below
the large sandy area to the left of the river. In between these
two locations, the river crosses a sediment-buried ridge that is
part of Iceberg Reef.
This rapid emerged briefly in the summer of 2008 and
for a while formed “The Wave”. The ridge that the river crosses
shows up as the small elongated island that was visible in the
In the Jan. 2009 photograph, there was a large muddy
area where the river was building its delta out into the lake. By
July 1, 2009 the lake level had dropped some 15 feet. The mud was
exposed and subsequently dried out to form the whitish sandy area
in the July 1 photograph.
Meanwhile, the river extended its path further out
into the lake, and in the process, crossed another buried ridge.
As the lake level dropped, the river eroded down thru the silt and
sediment until it hung up on the top of the old ridge. A new
rapid, Burro Spring Rapid is the result. Its location can be seen
in the photo where the river turns to the right and exits the
sandy area. ( A close-up of Burro Spring Rapid can be seen
Hiatus – Jan. 11,
The photo above was taken on Jan. 3, 2012 by Brady
Black and posted in the Mountain Buzz forum at http://www.mountainbuzz.com/forums/f11/pearce-ferry-rapid-35506-7.html
There was still a noticeable current at the rapid, but this was
due to the channel constriction between the rock and “North Point”
as opposed to any elevation drop of significance at the rapid.
Despite the current low snowpack levels in the
Rockies, Lake Mead is expected to rise a little higher yet than
what prevailed at the beginning of 2012. This plus the unrelenting
silt accumulation should mark the end of the rapid.
R.I.P. oh mighty rapid.
May 2015 Update
The continued long term drought in the southwest has
caused Lake Mead to drop to its lowest levels since it was being
filled in the 1930s. The rapid at Peace Ferry is fully exposed and
is quite severe again. A new rapid may develop a short distance
upstream from the former Driftwood Island ( See http://www.durangobill.com/GCTourLowerSuperimposition.html
“The Wave” rapid just below Iceberg Canyon should be
fully exposed and may become severe by late summer 2015. (And may
be unrunnable in 2016.) It looks like river current exists until
you pass Sandy Point. South Cove may become unreachable by boat in
Origin of this
There is a mythology about the origin of scientific
investigations regarding any subject. Cartoons sometimes show
someone in a white coat shouting “Eureka! I’ve found it!”
In reality, it’s closer to stumbling upon an
unexpected anomaly and not knowing what caused it. (As in a
quizzical: “That’s funny?”) This leads to a sequence of questions
such as What?, Why?, etc. Curiosity about the What?, Why?, etc. is
followed by a little research to try to find out what is going on
and what it might lead to.
The picture above is a Print Screen image of a
message that the author posted in Yahoo’s “Grand Canyon Rafting”
Group back in June 2007 – and now you know the rest of the story.
Notes on the
origin of the name “Pearce Ferry”
“Grand Canyon National Park,
Arizona. Upstream toward the west portal of the Grand Canyon.
Note the ruins of the old stone house in the foreground. This
was once one of the buildings at Pierce (Pearce) Ferry, where a
wagon trail from Kingman to Moapa crossed the river. Colorado
River Survey of 1923 (Birdseye).”
The historic photograph above was originally taken on
the “Colorado River Survey of 1923” and was subsequently published
in the May 1924 issue of National Geographic Magazine. You can see
the original photo at http://libraryphoto.cr.usgs.gov/cgi-bin/show_picture.cgi?ID=ID.%20LaRue,%20E.C.%20%20771
If you click on the photo at the above web link, you can get
The estimated location of the photographer is about
36.130 N, 113.977 W or about 0.63 miles east and a little south of
the developing Superimposition Rapid. (Please see the pin location
in the first Google Earth picture.) The view in the 1923
photograph looks slightly north of due east. Based on the
estimated location of the photographer and the location of the
river in the photograph, it is estimated that the river originally
turned toward the north just off the left edge of the photograph,
and passed about one-half mile to the east-northeast of the new
After Hoover Dam was built, the old river channel was
buried under 300 feet of silt and sediments brought down by the
Colorado River. You can get some idea of the magnitude of 300 feet
of sediment by following the ridge that starts in the dark shadow
next to the river and climbs to where it disappears off the right
edge of the photograph. The uppermost portion of this ridge (just
off the right edge) remains barely above the silt flats. If you
look at the first Google Earth picture, you can see a small
light-colored “sand island” to the right and a little below the
pin location. The “sand island” is the top of the ridge that is
just off the right edge of the 1923 photograph. Also, the “sand
island” is visible just to the right of the river in the middle
distance in the first 2006 Bureau of Reclamation photograph.
The picture above was generated by Google Earth and
shows approximately the same view (with slightly wider sides) as
the old 1923 photograph, except that as of 2004, the viewpoint is
some 300 feet higher due to the influx of silt. In the Google
Earth picture, the low flat area on the skyline to the left of
center appears relatively higher due to the ~300-foot increase in
viewpoint elevation. Most of the skyline is formed by the inner
rim (Grand Wash Cliffs), but the low flat area is part of the
outer rim and is some 5 - 6 miles more distant (and 1,900 feet
higher) than the inner rim. Thus the increase in viewpoint
elevation makes it appear somewhat higher in the Google Earth view
vs. the 1923 photograph.
The name “Pearce Ferry” goes back to 1876 when
Harrison Pearce established a ferry service here to cross the
river. There is good original documentation at:
The spelling of “Pearce Ferry” was subsequently
corrupted to “Pierce Ferry”. (The “spelling checker” in Microsoft
Word didn’t exist yet.) While “Pearce Ferry” (also “Pearce’s
Ferry”) is the original name, “Pierce Ferry” is widely used.
The picture above is a portion of the USGS 1892 “Mt
Trumbull” topographic map. The river flows from the Grand Canyon
in the lower right corner up toward the upper left corner where it
turns left through Wheeler Ridge before exiting off the upper left
edge. The original of this and other archived USGS maps can be
USGS maps in 1892 didn’t have anywhere near the
accuracy of present day maps, but when you think about it, any
reasonably accurate map in 1892 was a major accomplishment. The
old wagon trail from Kingman to Moapa is marked on the map as well
as the location of Pearce (Pierce) Ferry.
river miles 272 to 280
the Lower Superimposition Rapid page
to the Index Page for the Grand Canyon Tour
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