Cañon Retumbido or Echo Amphitheater is a geologic curiosity where one may go to play with voices. The formation is caused by the action of water cascading over colorful cliffs creating a large concave hollow. From an approach of about 500 feet distant, one can shout for echoes. The feature has streaks of desert varnish from the dribbling of water after sudden rain downpours.
The system of cliffs throughout the region is generally banded in different colors. Starting from the bottom, there is a layer of red. Geologists call it the “Chinle Group” after Chinle, Arizona, on the Navajo Reservation. It is made up of red siltstone and fine sandstone.
On top of this is 200 feet of fine grained sandstone called the Entrada Formation. It starts with a thick orange layer, then a thin white one, and then a thick yellow one. The Entrada layers were a super thick field of sand dunes with no fossils.
On top of them, pools of brine water formed and made the Todilto Formation. This formation can sometimes have fossils in its thin layer of limestone which is capped by a layer of gypsum. Nearby, the gypsum is so thick it forms light grey domes sculpted by gullies. Hispanos and American Indians used limestone (Spanish: cal) for preparing a kind of dent corn called maiz concho for making posole, a tasty local dish almost the same as southern hominy. Gypsum (yeso) was useful for whitewashing walls of houses. Hard balls of gypsum, called jaspe by the locals, were the best. One man told me that as a boy they cooked these in an oven and they crumbled into a bleach white powder. Mixed with water, a piece of sheepskin with the wool still on was used to paint walls with this non-toxic coating that brightened a room.
Above are multiple layers of calcrete, sandstone, siltstone and mudstone called the Summerville Formation. This layer has many bands of grey, red, and yellow dirt that form slopes rather than cliffs, about 300 feet high. Some fossils are found in these layers.
The campground was the scene of controversy in October 1966 when local Hispanos in an organization called the Alianza Federal de Mercedes, occupied the campground after unsuccessful petitions to the government to address grievances over land, natural resources, and grazing rights. Declaring a semi-sovereign governing township, members of the Alianza held meetings and elections. When forest rangers attempted to evict the occupiers, the rangers were arrested by citizens. After further events involving controversy, violence, and court trials in other locations, the US Government ultimately responded by increasing public welfare assistance and entitlement services in the region.