Geological History of Canaima.

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map_angel_fallsHistory of the geological formation of the National Park Canaima.

The National park is part of the plateau of the Guyanese shield that underlies the entirety of the lands located in  Venezuela to the south of the Orinoco, it is composed of three main geological formations. The oldest is an underlying igneous-metamorphic basement formed some 1.2-3.6 billion years ago whilst South America was joined to Africa as the supercontinent Gondwanaland. Between 1.6 and 1 billion years ago, this was overlain with a sedimentary cover. The first of these formations is too deeply buried to be visible within the park, but second (known as the Roraima Group) forms the basis of the area's extraordinary topography (Huber 1995). It consists of quartzite and sandstone strata which were probably laid down in shallow seas or large inland lakes (Briceño et al. 1990) during the Pre-Cambrian period. Lastly, during Palaeozoic and Mesozoic times magma repeatedly penetrated the existing sediments forming intrusive rocks which are typically diabases, and to a lesser extent granites.

The tepui formations, not unlike those found in the deserts of northern Arizona, came into being by a process of erosion of the surrounding lands over millions of years. The tepuis are sandstone massifs, and it is thought that what are today mountains once formed harder or less faulted strata which were more resistant to erosion.

There is an impressive array of different soil types. The low mineral content of the parent rocks of the Guayana Shield, the high rates of weathering that occur in tropical climates and the age of the sediments has produced soils which are generally acid and nutrient poor. Only where there are more basic igneous intrusions are the soils capable of supporting luxuriant forests or cultivation.

One third of the plants are found nowhere else on the planet

These important changes can be experienced in the geographic area where the Canaima National Park since its inception.

What you see today is the result of a long geological transformation over time has even today. With two billion years back to the days when it was forming the super continent Pangaea, which includes America, Africa, Antarctica, Asia and Europe.

The continent began to separate due to the bill for the crust of the earth thus causing the formation of the Atlantic Ocean, creating the different parts that we call shields. The geographical area of the Guayana Shield, existed from the beginning.

It began as a Great Plains of flat land, whose height was the same as that of the Tepuyes visible today, from about 2000 to 3000 meters high.

The formation of these lands are caused by erosion, which is the movement of different types of materials, traveling moved by the force of the strong water currents carrying rocks and minerals at different places.

These materials were deposited creating a database of igneous and metamorphic rocks coming from the crust that originated. These particles, produced by the erosion of crystalline rocks were consolidated in layers.

Quartzite and shale, these stones covered many kilometers of the crust, erosion moved a large part of the crust and the strange land were higher than they are known as Tepuyes which we see today on their surface planes with their own world in top.

old mapIn places where deposits of materials occurred in a certain order are highly resistant rock formed. In other places were deposited in a disorganized manner were less resistant rocks.  After the formation of the Great Plains, over a long period of time (about 400-200 million years) a series of climatic changes caused significant changes in the Guayana Shield. The transformation of the landscape is mainly due to the drastic weather changes from dry to wet and vice versa, to high, low and constant rainfall, drought, frost, shock of high and low temperatures, storms, hurricanes and Teutonic movements of the planet.

The erosion of the weather was removing material deposited in the great plains for millions of years. In places where the rock was less resistant erosion was higher, being a result of this great transformation, because of that the Tepuy and landscape of the Canaima National Park have their fantastic appearance as of today.

Written by :
Henrik Bratfeldt
 
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