The recent holiday season saw the first expedition to Cerro Grande in Jalisco/Colima, Mexico in over ten years. The Cerro Grande area, part of the Sierra Manantlan, is a well karsted plateau with slightly more than 100 sq. km at an elevation of over 2000m (the high point is over 2400m). The limestone appears to bottom out at about 500m elevation giving the plateau tremendous potential to host a kilometer deep cave. The area was first worked by a group of Mexican cavers headed up by Carlos Lazcanos, aided by some visiting French cavers, in the earlier 80's. By 1985 they had documented some 85 caves in the area, mainly pits, with six having drops over 100m and one a single 240m pitch, as documented in Lazcano's book, Las Cavernas de Cerro Grande, Estados de Colima y Jalisco (out of print). But none of them would break that 240m depth level. Having heard the tales from local cavers after moving to Guadalajara I decided that it was time to have another look, for surely there must be at least one route that goes all the way through.
So accordingly, invitations went out to friends in four different countries only to find that most were too impoverished to come (or even send a note saying so). Complicated Internet communications (Mexico is a little quirky in this regard) managed to co-ordinate the arrival of one group of Brits from the BEC and the newly formed SCC. The final team was Andy and Angie Cave, Henry Bennett and Skippy Gerard of the BEC, Richard Blake and Vince Simmons of the SCC (Southern Cave Club), Alexandra Taylor and Vicente Loreto of the U. of Guadalajara and Canadian Chris Lloyd. We were joined for a few days by Nick Hawks (a British geologist newly resident in Guadalajara) and his wife and one year old daughter.
We had a beautiful campsite in an opening in the pine forest off a side road north of the town of El Terrero with dolines dropping off in three directions. The density of dolines there was quite impressive, especially once you realized that all those 10m to 80m diameter dolines were merely small holes nested within km scale depressions. The big catch here is the soil development which once disturbed, by agriculture or logging or even the most benign of road building, easily erodes into the dolines clogging them up. This kind of soil development is quite unusual in limestone terrain and I believe can be attributed to ash eruptions from the nearby Volcan de Fuego, which is only 30km away to the north.
Once settled in at least two separate groups set off in search of pits to drop each day. One or two of the groups was accompanied by a local guide who always had a target or three to keep the team busy. Over the first eight days we managed to find and drop 42 caves, all vertical pits. The vast majority were just one single drop to a dirt floor and less than 20m deep. A few were multi-pitch leading us to think that we were really on to something, but they ended before getting 100m deep. The deepest cave was a single drop of 120m which Skippy lucked into putting the rope in the one possible place where it didn't touch the wall the whole way down.
One cave was of note for its size, 50m deep but some 30m by 15m across, which was dropped by Andy Xmas day in the rain. A good effort that considering that the big to-do in Mexico is Xmas eve. To save placing an awkward bolt for a rebelay a long line was thrown in as a deviation. This technique to achieve a free hang was employed numerous more times as the majority of pits had slight slopes and then dirt right at the lip. It was also nice in that it could be easily adjusted once the person was on the rope and could see better down the pit to just where the rope should go.
Six entrances were located that were blowing air and didn't have the standard collection of flies coating the walls. In some caves these flies almost resulted in suffocation of those unprepared with full face coverings. One of the blowing holes was un-enterable even after enlarging while another went down only a 3m deep squeeze. Two others managed two short pitches to about -30m, while the last two had five pitches down to -70m and -90m and then lost the air flow. One of these (Roadside Pit) needs some drilling to gain another pitch while the other needs a skinny, determined pusher to see it to its end.
Two other blowing entrances were described to us by the locals but not located and it is these types of entrances that future parties should concentrate on. For our, and previous experience, has shown that if they are not blowing they will end in a dirt floor or even in one case bad air.
In terms of area covered - the previous parties from the early 80's looked at about 10-15 sq. km, all along the main roads of the time. This expedition covered about 6 sq. km well and skirted through another 6 sq. km. That still leaves some 70% of the plateau to be examined. Certainly ample room to hide one through going cave.
In terms of access for future parties, things are a bit complicated, but not impossible. Since the explorations in the early 80's a large portion of the plateau has been incorporated into a National Biosphere Reserve (though just which parts are not clear, and not even the biologists administering it can show you a map of what they are supposedly administering). This was the result of the discovery of a perennial type of corn - possibly the mother of all corn, along with a very high diversity of other plants. This reserve is under the administration of the U. of Guadalajara biology department who have established a research station in the town of El Terrero. By my reckoning, the establishment of this preserve (IE. No cutting of trees or growing of corn) and the subsequent intrusion of the U. de G. researchers caused quite a disturbance with the local people (no surprise). They have by now established a good working relationship and level of trust. But the local people have now become somewhat to very hostile to outside people coming to tromp around in "their" woods and "their preserve". Lazcano and company had no such problems so it is obvious who has changed the attitude of the local people.
The bottom line is that there are two groups of people that future explorationists must deal with, and it is suggested to start with the mayor of the local ejido and get his blessing first and the rest should sort itself out in due course. A nephew of the current mayor, Oscar, was our guide and was trained by us and would be thrilled to have other parties come up so he can do some more caving. He is also a field assistant for the researchers so is out walking the woods all the time and now knows exactly what to be looking for. The best time of the year is dependent on whether you want warm and wet or cold and dusty. July through Sept. is the warm and wet time, with May and June being the peak of the dry and hot season. At Xmas we had heavy frosts almost every night or else rain with very pleasant sunny days. It is possible to drive to the town of El Terrero on the plateau in about four - five hours from Guadalajara, or one hour from Colima, in any kind of vehicle. Driving past El Terrero does require a vehicle with good clearance, such as a pick up truck, though four wheel drive is not necessary.
We still believe that there is a deep cave hiding up there somewhere and more perseverance will eventually be rewarded. There are two major known resurgences located at the north and south end of the plateau. Nearby the northern one is Cueva Toxin, which at 3km long is the longest cave in Jalisco, and not considered to be fully explored. Obviously something is feeding these outlets, it is just a matter of cracking through that seemingly impenetrable -230m level. All the areas we explored were disturbed by the hand of man and recently silted up small dolines were very evident. Even less than five years ago some of these likely had open entrances. The areas of the actual biosphere reserve are supposedly protected form further disturbances and thus may prove to be a productive place to be checking for blowing holes. There has to be one up there somewhere.
Chris Lloyd
Feb. 1996 - Published in the AMCS Newsletter No. 22, 1997