Sumidero Canyon () is a deep natural canyon located just north of the city of Chiapa de Corzo in the state of Chiapas, in southern Mexico. The canyon's creation began around the same time as the Grand Canyon in the U.S. state of Arizona, by a crack in the area's crust and subsequent erosion by the Grijalva River, which still runs through it. Sumidero Canyon has vertical walls which reach as high as , with the river turning up to 90 degrees during the length of the narrow passage.
The canyon is surrounded by the Sumidero Canyon National Park, a federally protected natural area of Mexico which extends for over four municipalities of the state of Chiapas. This park is administered by the National Commission of Protected Natural Areas (CONANP). Most of the vegetation in the park is low- to medium-height deciduous rainforest, with small areas of mixed pine-oak forest and grassland. At the north end of the canyon is the Chicoasén Dam and its artificial reservoir, one of several on the Grijalva River, which is important for water storage and the generation of hydroelectric power in the region.
The canyon and national park is the second most important tourist site in Chiapas, drawing mostly Mexican visitors who see the canyon from boats which embark on the river from Chiapa de Corzo. The park borders Tuxtla Gutiérrez, the state's largest city, which has caused problems with human encroachment and settlement on park land. More importantly, the urban areas and logging industries upstream from the canyon have caused serious pollution problems, with up to 5000 tons of solid waste extracted from the Grijalva River each year. This waste tends to build up in the canyon because of its narrowness, the convergence of water flows and the presence of the Chicoasén Dam.
Description
Geology
The Sumidero Canyon was formed by cracks in the Earth's crust along with erosion by the Grijalva River, which still flows through it. The process of its formation began about 35 million years ago, making the Sumidero contemporary with the Grand Canyon on the Colorado River. The Grijalva is the main water system in the area, beginning in the Cuchumatanes in neighboring Guatemala. The river then flows through Chiapas, including the 13-km length of the canyon, from south to north, then on to Tabasco before it empties into the Usumacinta River. This river basin is one of the two most important in Chiapas, and one of the most important in Mexico with a total river length of approximately , draining an area of , with an average flow of about forty million cubic meters.
In addition to the Grijalva, there are other flows of water in the area in and around the canyon, many of which are seasonal. These consist of streams, some of which form waterfalls on the canyon's sides, and underground movements which have created caves and karst formations. The last important water formation in the area is the manmade reservoir of the Chicoasén Dam.
The canyon proper is deep and narrow, characterized by vertical walls. As the gap changes direction as much as 90 degrees in places, it separates the Meseta de las Animas mesa in the west from the Meseta de Ixtapa mesa in the east. The width of the canyon varies from . Most of the canyon's walls are between high, reaching at their highest point. These walls expose a long process of disturbance in the Earth's crust with layers of limestone from the Upper Mesozoic, which contain fossils of marine creatures. During the Mesocretac Period, there was an elevation of ocean floor which formed much of the mountains of the area.
Notable features
The interior of the canyon has thirty rapids, five waterfalls, three beaches, two freshwater springs and a cofferdam three meters wide. The canyon contains endangered and threatened species such as the Central American river turtle and the American crocodile, which can be seen on the riverbanks. The walls of the canyon contain numerous small caves, rock formations and other notable features. The best known of the area's caves is the Cueva de Colores ("Cave of Colors"). This cave gets its name from the filtration of magnesium, potassium and other minerals which form colors on the walls, especially shades of pink. It contains an image of the Virgin of Guadalupe inside usually surrounded by fresh flowers and burning candles left by visitors. The Cueva de Silencio ("Cave of Silence") is so named because of a lack of echo or any other kind of resonance in its interior. In another small cave, there is a stalactite called the Caballito de Mar or "Seahorse" after its shape. Of the various seasonal waterfalls, the best known is the Árbol de Navidad ("Christmas Tree"). The "branches" of the Árbol are made by deposits from the waterfall which have been covered in moss. During the rainy season, when the waterfall is active, the water and the light change the colors of the "branches" and make the formation stand out. The park was a candidate in 2009 as one of the Seven New Natural Wonders of the World.
Climate Despite its biological, ecological and cultural diversity, there have been few studies performed in the park area. For this reason, there is a lack of information about species, habitats and water flow. There is also relatively little information about how human activities affect the park.
As the park is located in the Central Valley of Chiapas and borders the Northern Mountains region, altitudes vary from approximately above sea level in the municipality of Chiapa de Corzo to above sea level at the El Roblar lookout point. This geography produces a channel for air flow from northwest to southeast as well as three main climates based on the Köppen system as modified for Mexico. These are hot and dry (where airflow is blocked), semi-hot and humid, and hot and humid. The average rainfall for the park is about 1,000 mm during the rainy season from May to October and 200 mm during the dry season from November to April. Average annual temperature is 26 °C. The rugged terrain also forms a number of microclimates.
Vegetation
Most of the park's vegetation, especially around the canyon, is dense tropical rainforest. Most species found in the park are members of the family Fabaceae with 59 species and the family Asteraceae with 25 species, which reflect the abundance of these families statewide. Other important families include the Orchidaceae and Euphorbiaceae, each with 22 species, the family Convolvulaceae with 17 species, and the Cactaceae with 11 species. 122 species are considered valuable as ornamental plants with 46 having medicinal uses and 31 species valuable for logging. These mostly come from the rainforest areas. The rainforest vegetation is mostly deciduous, shedding leaves in the dry season. However, there are perennial rainforests, forests of pine and oak, grasslands (mostly induced) and areas with secondary vegetation.
The three main vegetation classifications are low-height rainforest, medium-height rainforest (as per the size of the trees), pine-oak forest and meadows. Medium-height deciduous rainforest is mostly located on either side of the canyon, in the north and east of the part towards San Fernando and in the Cañada Muñiz at altitudes of between 150 and 1250 masl. It is mostly found in areas with basalt or granite rock and where there are lime deposits, covering an area of in total. While many plants here loose leaves in the dry season, there are some that retain them year-round. Maximum height of trees varies between 25 and 30 meters. The density of the tree cover in these areas is enough to lower temperatures on the ground in the summer rainy season due to the maximum foliage which occurs at this time. The tree cover is composed of the following species: breadnut (Brosimum alicastrum), guanacaste (Enterolobium cyclocarpum), totoposte (Microdesmia arborea), jocotillo (Astronium graveolens), cedar (Cedrela odorata), cuaulote blanco (Luehea candida), hormiguillo (Platymiscium dimorphandrum), chicozapote (Manilkara zapota), tempisque (Sideroxylon capiri) and various types of amate fig trees (Ficus spp.). Under the tree cover, there is significant plant diversity, including palms and araceas. Epiphytes (air plants) are abundant as well, along with orchids, Bromeliaceae and cactus. Cactus are primarily found on the vertical walls of the canyon and belong to the Acanthocereus family. In the 1970s, tree area in a good state of conservation amounted to , or 17.72% of the total land area. From 1988 to 1993, this amount was reduced to , or 5.35%. From 1990 to 2000, it is estimated that eight percent of the remaining forests and 38% of the rainforests were damaged. Many of the areas in good condition are broken up by disturbed areas. Most of the damage is due to illegal logging and the clearing of land for pasture or agriculture. Medium-height perennial rainforest (also known as evergreen cloud forest) exists only in small dispersed patches, mostly on the sides of the canyon in contact with the Grijalva River. Many of these patches are less than one hectare in size, as they are located on small areas of flat land at altitudes between 1000 and 2,500 masl. The soils are rich in undecomposed plant matter which holds in moisture. Low-height deciduous rainforest is mostly found around the La Ceiba and La Coyota lookout points in the south and southeast sections of the park, with some in the east towards the La Chacona Cañada. These occupy a territory of in the park. Tree heights extend from four to ten meters with some as high as 15 meters. Non-tree species are not as common and mostly consist of succulent species such as Agave, Opuntia, Stenocereus and Cephalocereus. Other important species include Alvaradoa amorphoides, Bursera simaruba, Ceiba aesculifolia, Bursera bipinnata, Bursera excelsa, Cochlospermum vitifolium, Haematoxylum brasiletto, Piscidia piscipula, Swietenia humilis, Acacia collinsii and Pseudobombax ellipticum.
Pine–oak forests exist in the northwest of the park in the highest altitudes, covering about . They are part of the same type of forest found in the Soyaló region it is adjacent to. They are found at an altitude of 1,200 masl and above in areas that receive precipitation of about 1500 mm annually. The most common species is the oak Quercus acutifolia (syn. Quercus conspersa), often found mixed with the two kinds of rainforest found in the park. Air plants are common here as well as bromeliads, orchids and plants from the Maxillaria, Lycaste, Cattleya and Laelia groups.
Grassland is not naturally occurring but rather exists due to human activities such as farming and livestock raising. It is seen on the north and south sides of the canyon and is usually associated with secondary vegetation such as Tecoma stans, Gliricidia sepium, Plumeria rubra and Acacia collinsii, occupying an area of in the park.
Wildlife
Throughout the history of the area, especially since it was definitively explored in the 1960s, the area's wildlife diversity has been severely negatively impacted by human encroachment in the form of settlements, agriculture and hunting. However, since the federal park was established in the 1980s, wildlife diversity has increased. In 1986, the federal Secretaría de Agricultura y Recursos Hidráulicos (SARH) reported a total of ninety species of vertebrates divided into four species of fish, one amphibian, 14 reptiles, 26 birds and 40 mammals. A 2005 study indicates 308 species with four species of fish, 15 amphibians, 195 birds, and 53 mammals. Between these two, there have been a number of other studies which also show the growth of the number of wildlife species in the park.