Jaramillo Petrified Forests National Park

Barely 150 million years ago, the Jurassic period featured dense forests with gigantic trees, some of them relatives of the phones or araucarias…

Jaramillo Petrified Forests National Park, Argentine

But at the beginning of the Cretaceous, the tectonic movements that caused the mountain range to rise and coincided with the volcanic eruptions ended up burying several extensions of Patagonian land. Among them, many forests that, being covered with ashes, began the process of petrification. Over time, the wind and rain discovered some areas of these petrified forests, among which the araucarias stand out, reaching 35 meters in length and 3 in diameter, probably the largest known in Argentina and the world. world.

In 1954, they were declared a Natural Monument, to protect one of the best examples of petrified forests in our country. It has an area of ​​15,000 hectares northwest of the province of Santa Cruz, 135 km from the town of Jaramillo. Likewise, the National Parks Administration has acquired two adjoining ranches and steps are being taken to include them in the protected space, expanding it to almost 60,000 hectares.

On December 27, 2012, Law 26,825 was enacted, creating the Petrified Forests of Jaramillo National Park.

The extremely undulating relief is surrounded by high plateaus. To the southwest, the Madre and Hija hills, with only 400 m of altitude and basaltic texture, the result of prehistoric volcanic activities, reign over the landscape presenting the appearance of a hill.
In the lower sector, the shallow Laguna Grande appears and disappears depending on weather conditions. Its formation originates from the accumulation of water from the few but intense rains and undergoes rapid evaporation due to the impermeability of the soil, the great sun exposure, and the continuous wind.

Medusa’s gaze

Far from the myths, petrification, as well as other natural phenomena, is the result of long transformation processes and the confluence of multiple factors.
We go back to the middle Jurassic period when the volcanoes convulsed the hot and humid Patagonian environment. The successive ash rains and stormy winds suddenly covered the trees and other living organisms, allowing their conservation for millennia.
Then the precipitation, loaded with silicon salts, passed through the ashes and penetrated the plant tissues, initiating the substitution process. In this way, organic matter was replaced by mineral inorganic matter, a process known as mineralization or petrification.

The most surprising thing is that the trees were fossilized in the same place where they spent their entire lives, finding specimens with their roots and the basal part of the trunk standing, as well as others oriented from east to west. For this reason, it received the name petrified forest. It is considered unique in the world because the other deposits, located in different regions, were destroyed by both rivers and glaciers.
According to studies, the estimated age of some specimens would be around 1000 years before petrifaction, which must be added 150 million years to our time.


The Patagonian steppe presents this region with its typical vegetation, which barely covers the ground, acquiring the appearance of a desert. The aridity of the soil is so great that the adaptation of the flora to such adverse environmental conditions is truly surprising. The sparse and stunted vegetation, from a very diverse taxonomic position, takes compact and semicircular forms, covered by a thick cutin that reduces evaporation. Under this aspect, if the winter had significant rainfall or snow, in spring cacti with large orange flowers and various kinds of daisies in yellow and, more rarely, white-pink colors are distinguished by their beauty. If, on the other hand, the winter season was dry, the process is reversed: there is no germination or regrowth and, consequently, the flora does not develop.

Shrubs grow on the canyons that reach up to 3 m in height, such as moles, duraznillos, bitter coirones, Patagonian carob trees, black bushes, colapiches, and calafates, among others.
In environments of almost permanent humidity, such as small mallines, reeds grow and, in more desert areas, only a few lichens and small shrubs with reduced leaves proliferate.

Close to the trails of petrified monkey puzzle trees, small herds of guanacos can be seen. The population of these herbivores is closely linked to the availability of vegetables because the long periods of drought cause great mortality among these animals. In turn, they are persecuted by ranchers in the area, arguing that they compete with domestic cattle for pasture and water.
Another herbivorous mammal is the mara or Patagonian hare, displaced in part by the European hare, which also inhabits the territory of the Petrified Forests Natural Monument.

Among the predators, we find the wild cat, the pajonal cat, and the puma, which the landowners stalk because they consider them a strong impact on the cattle. Gray and red foxes are the area’s minor carnivores, highly coveted for their fur. The skunk and small diggers such as the Patagonian piche, the chingolos, and the lizards of various shades also inhabit the place.
The birds that are home to the region are the shorty rhea or rhea, a symbol of the austral ratites, partridges such as the copetona and the Patagonian keú, the carancho, the black-chested eagle, and other typical species of the steppe bushes such as the Patagonian and the black-tailed cunt.

In prehistoric times, there were populations of hunter-gatherers who, favored by the diversity of microenvironments in the area, had resources inaccessible spaces with short trips: water throughout the year, shelter, firewood, good visibility, and animals such as guanacos and rheas to the hunting. The abundant availability of rocks to carve, allowed them to make different elements. Numerous settlements, riding schools or workshops, base camps, burial sites, and quarries were found for the extraction of raw materials, including fossil wood that was selected for the manufacture of stone instruments.