NOTES
ON PREPARATION OF MEXICO LIST
-Andy Martin
In October 2004 I completed a project to list the
50 most prominent Mountains of Mexico. The list is
found at the bottom of this email, and at
http://groups.yahoo.com/group/prominence/files/Mexico
This write up discussed several aspects of this
project:
Climbing challenges
Peak distribution
Possible biological islands
List preparation and errors
For more info on prominence see www.cohp.org or
www.peaklist.org.
- Andy Martin,
Tucson Arizona
I. Climbing Challenges
Eight of the listed peaks are described in Kelsey's
World Mountains guide: (number is position on
prominence list)
( 1) Orizaba
( 2) Popo
( 3) Colima
( 4) Toluca
( 7) Diablo
( 9) Malinche
(24) Ixty
(45) Perote
Another peak that may be known to climbers is (10)
Sierra la Laguna.
Bob Packard Robert.Packard@nau.edu has climbed
these, plus
(19) Virgenes and (37) Sandia in Baja, making him
the leading
climber of these peaks to the best of my knowledge.
This leaves about 40 peaks that are unknown to most
hikers on the planet. The most exciting part of this
project was looking at big peaks formerly unknown to
me,
and plotting out potential routes to the summit.
One that looks difficult is (26) Sierra el Cerro
Azul, a possible
ultra at 4,921+ 131. This summit is isolated, has
steep flanks, and
probably is covered by dense vegetation, as it lies
in the'
tropics.
There are also some challenging desert peaks near
Monterrey
that appear to require 5,000 feet vertical gain while
bush wacking up rugged limestone terrain. The
Monterrey region boasts
the densest cluster of peaks on this list, claiming
nine
of the 50 within 75 miles of the city. Monterrey is
perhaps 300 miles from San Antonio Texas, and thus
these
Texans are the best situated to explore big
prominence
peaks in Mexico.
On the opposite extreme of difficulty, the
interestingly
named (25) Volcan de Tequila near Guadalajara has a
microwave
access road to top.
It is interesting for me to contemplate the "future"
of this list. The high point list of the 32 Mexican
States
(16 have big prominence) was published in 1991 and
has attracted
little interest to date. Hopefully this new list
will have at least
one climber tackle it in the next decade.
II. Peak Distribution
Plotting the first fourteen peaks listed (these have
6K prominence)
identifies four major areas with big peaks.
The most striking is a belt of 5 big volcanos
slashing
from coast to coast through Mexico City. From west
to east
they are (3) Colima, (4) Toluca, (2) Popo, (9)
Malinche and (1) Orizaba.
Just south of this following the coastline are 3 big
"unknown"
peaks (8) Conchas, (5) Tiotepec, and (6)
Nacimiento/Flan.
Near Monterrey are (11) Madera, (12) Chena, and (14)
Rafael/Morro.
Rafael/Morro is over 12,000 feet high and has great
"isolation", being over 300 miles from any other
peaks
reaching this height.
Baja is anchored at the top by (6) Diablo and bottom
by (10) Laguna.
One surprise is the lack of big peaks in NW Mexico,
This part of Mexico is made up of Sonora,
Chihuahua and Sinaloa, and is a rugged land with
many peaks
over 9,000' elevation and big canyons. However, it
has very
little in the way of big prominence, with only the
little
known (49) Sierra Alamos and even lesser known (43)
Cerro
Los Algodones making the top 50 cut of 4,265 feet
prominence.
By comparison, Arizona has 9 peaks that surpass this
standard.
III. Possible Biological Islands
Prominence is a useful tool to identify biological
"islands",
with plants and animals isolated on high ground that
is surrounded
on all sides by much lower terrain. Often these areas
harbor unique species.
Other factors that we look for here are peaks with
large
areas of high ground, as opposed to a sharp summit.
We expect peaks surrounded by large rivers or even
oceans
to have more biological isolation. Finally, peaks
that
have tops far above timber line, perhaps even
glaciated,
will not have as many species living near the summit.
Taking these factors into consideration and looking
only
at the top ten peaks listed, possible biological
islands are:
Cerro Tiotepec
Nacimiento/Flan
Picacho del Diablo, in northern Baja.
A large area of high ground lies
to the west of the peak.
Cerro las Conchas
HP Sierra la Laguna, at tip of Baja, and surrounded
by ocean
on 3 sides. Known to have unique
species.
IV. List Preparation and Errors
The University of Arizona has a very good collection
of
1:50,000 scale maps for all of Mexico. I relied on
these
for elevation and naming information. These were
prepared by the Mexican mapping agency in the 1970s
and
1980s time period. They normally use 20 meter
contours
in mountain areas, and 10 meters in flat lying
ground.
I have found them to be fairly accurate on a few
hikes south of the border, though they can "hide"
bothersome cliffs in some cases.
Road info on these maps is not always reliable.
Mexican place names seem to be somewhat variable,
and it is unknown if the names found on the 1:50K
maps are the most authoritative.
My biggest problem with these maps was the lack
of spot elevations. Most do not have a single spot
or benchmark elevation on the quad, but only labels
on the 100 meter index contours. Sometimes
the 100 meter labels are incorrect, which of course
causes problems.
The lack of spot elevations on peaks or saddles
means that most prominence values fall into 20
meter (65.6 feet) "brackets". This leads to lots
of ties of course, and helps explain why six
peaks below the top 50 cut off are still possible
members of the top 50 set. Note that saddle
elevations
are not listed, but can be computed by subtracting
prominence from summit elevation. For example,
on Popo we have:
summit: 17716+
66
- prom: 9908+ 131
___________________
saddle
7808- 66
This means the Popo saddle lies up to 20 meters under
the 2380 contour shown on the 1:50K map. The summit
has
an minimum elevation of 5400 meters, with up to 20
meters additional height. The minimum prominence
is 3020 meters, with up to 40 additional meters
possible.
While the 1:50K maps were essential to provide
detailed
peak information, I also relied on the 1:500,000
scale
Defense Mapping Agency Aerospace maps purchased from
NOAA.
My set dates from the mid 1980s, and was used in
identifying
which peaks might have 4,000' prominence, and thus
required
further checking on the Mexican quads. These air
maps usually
have elevations given for summits, but these values
differed widely from the 1:50K values. Usually they
are
higher, as you would expect on air maps. However,
on (31) Zamorano, the air map (TPC J-24B) shows
10,760'
and the Mexican map has 11,023+ 66. Hopefully pilots
using the air map elevation in the vicinity of
Zamorano
are flying extra rugged aircraft ;)
This same air map shows a major river flowing up and
over an important saddle just south of lake San
Ignacio
Allende, 40 miles west of Zamorano. The Mexican
topos do a much
better job here, showing the river flowing through
a canyon, and relocating the saddle to the world of
fantasy.
Users of my Mexican State HP list will note that in
1991
a greater reliance was placed on air map elevations.
However,
a lot of quads were scrutinized since then.
In a list of this sort my main concern is that a peak
was accidentally left off, due either to a glitch in
the
air maps, or inadequate screening on my part. It
would not surprise me to learn that a peak or two
was not listed. However, Jonathan deFerranti has
used a
computer program processing SRTM data to
independently
list almost 40 of the peaks, without detecting an
omission.
In the future he plans to list peak in Mexico down to
2,000' prominence, which will allow a complete double
check.
Finally, those interested in an "eyeball bender"
exercise
can try to find the key saddle 5,052- (66) for peak
(40) Cerro Tzontehuitz on quad E15D84.
The flat lying karst terrain makes this a challenge.