A geological layer cake
The bridge marks the entrance of the old gorge that the Grijalva river flowed through before the dam was built. These days the true canyon begins beyond the bridge and the walls eventually rise to a staggering 800 meters, 2640 feet above you. At the Sumidero's elevation that's 900 meters above sea level. Apparently the river was not navigable prior to the construction of the dam because of swift rapids and cataracts in the narrowest parts of the passage. Below you can see a partial cross section of the limestone karst. The layers are riddled with little caves that drain water during heavy rains. Various birds nest here and the boat captain typically points out migratory birds whenever he sees them. The Sumidero canyon ecosystem is quite diverse and thankfully intact. The Sumidero Canyon ranks among the top vacation destinations in Chiapas.

      Christmas Tree Falls formation
We missed the most dramatic time to see this geological oddity but even in its dry phase it's obvious something unusual is happening. During heavy rains the water cascades down this section of cliff face from a drainage cave and the slope just above. Partial evaporation of the rainwater leaves a tiny bit of calcium on the rock. Over millenia the deposited calcium has built up to form these terraces in the shape of a Christmas tree. Moss and grasses cling to the overhangs.  more pictures in the rain

      Geological history
The Sumidero Canyon lies on a geological fault that formed during the Pleistocene epoch, 1.81 million to 11,550 ago. Geological faults are the result of earthquakes and the Sumidero may be the result of repeated seismic activity. It seems unimaginable that a single earthquake could create a chasm this large in the landscape. Seismic activity is still occuring, the last events being mild, magnitude 4.3 to 4.5 from 1986 to 1997.  aerial view of the canyon wall

      The ecological park
Out on the wider section of the Grijalva river, on its eastern shore, is a recently built ecological park Cañón del Sumidero Parque Ecoturístico. The park was opened in April of 2003. Actually there was an option by our boat tour provider to drop us off there for an addition fee that included entry. They have a main lodge, restaurant, gift shop and a lot more. Prices range from $16- $40 usd per person, depending on what you want included. Offered activities include: kayaking, abseiling, mountain biking, zip-line, swimming, bird sanctuary and an animal sanctuary. Access is only from the water and the view is beautiful.  more

      The Chicoasen dam—turn around point
The Chicoasen hydroelectric dam (aka. Manuel Moreno Torres dam) opened in 1981. Upon its completion it was the worlds 5th tallest dam at 261 meters. By Nov 2000 new generators were added and today the Chicoasen dam is Mexico largest producer of electricity. It is near the dam that the Grijalva river is at its deepest, ± 800 feet deep.  Chicoasen hydroelectric dam aerial

      End of the line
Needless to say, Chiapas is a long way from the Riviera Maya in Quintana Roo. Nevertheless there are wonderous things to see and do that make Chiapas well worth the effort for those who have the flexibility to travel around while there. Please follow the links below for more about one of Mexico's best kept secrets.