Today we are going to talk about a geological formation for which it is called witness hill. They are formed due to erosion and are usually found in flat areas. I have considered as the testimony of the passage of time the retreat and the evolution of a slope or a platform. It has several characteristics that are worth knowing as it explains a little about the dynamics of the earth's crust.
In this article we are going to tell you what a witness hill is, its characteristics and how important it is for geology.
What is a witness hill
It is a geological formation that is due to soil erosion over the years. We are talking on a scale of geological time so it cannot be evaluated on a human scale. The third witness is the one that reveals the evolution of a bet or platform on a flat surface. This surface consists of horizontal layers of soft and hard rocks where the continuous blowing of the wind has caused an erosion that has modified the terrain.
In the softer layers of the soil, erosion occurs more frequently. The rivers cause erosion and form different hills and other formations. If the plateau is eroded on all sides, what is known as a witness hill is formed. These hills have occupied these places for several million years.
How it is formed
These geological formations are sculpted by erosion and it is called the witness name because it is a testimony of the ancient extension of a horizontal platform that has been isolated. The differential erosion that has occurred due to rivers and ravines they are the hardest and softest sedimentary layers alternately. These witness hills are delimited by the escape of erosion characterized by a more abrupt part that is formed by hard rock and another softer part formed of soft rock. The hardest part is called the cornice and the softest part is called the slope.
The witness dog has a convex concave profile and varies depending on the resistance that the hard rock part and the soft rock part give it. When the erosion produced by the rivers increases, all sides are making the witness hill appear with the flat peaks. Therefore, they are witnesses of a platform that existed in that same place millions of years ago. The rest of the relief that remains is a set of hard and soft layers that are arranged horizontally and that erosion has been able to sculpt.
Where are the witness hills
They are quite common in the sedimentary basins of the different rivers. These formations can be found in the Pilot mountain, in North Carolina, in the Cerro de la Teta (Guajira Peninsula) and in the Dori plateau (Burquina Faso). In our country we can also find it in different tabular reliefs such as the Ebro river depression and in the sedimentary basins of the central plateau. In Madrid we have the Cerros de la Marañosa, in the Cerro de los Ángeles and the Buenavista, and in the province of Palencia, the Cerro del Otero.
We will describe the characteristics of the Cerro de los Ángeles. It is located approximately 10 kilometers from Madrid, in the municipality of Getafe. Thus he has considered it as the geographic center of the Iberian Peninsula. For this reason, it is of great importance despite the absence of a scientific measurement that supports it as such. On the esplanade at the top of this hill is the well-known hermitage of our Mrs. De los Apóstoles. This allows dating from the fourteenth century and is a fairly well preserved monument.
On the slopes of this hill there are Aleppo pine trees, playgrounds, a soccer field, different paths and a picnic area. This makes the Cerro de los Ángeles a pleasant tourist walk that is in contact with nature. Its base is 610 meters and reach a height of 666 meters. At the highest point is a first-rate geodesic vertex. It is excellent to be able to see all the views of Getafe, Madrid and the countryside that surrounds the municipality.
Key features
These witness hills can be classified as an island mount. Its main characteristic is having been preserved after the erosion that has dismantled the rest of the nearby materials. These island mountains they have been kept protected from erosion thanks to a more resistant lithology. They are quite useful for doing geological studies since they are the only ones that remain belonging to the other geological formations that previously covered the region. In order to make a time map of how the entire earth's surface has advanced after erosion, it is important to know the morphology of the relief at that time. Thanks to the presence of these witness hills it is possible to know.
These erosion and sedimentation processes are typical of the external geodynamics of our planet. These witness hills are also characterized by having been surrounded by water, which is why they are located in areas near rivers that are at an outlet to the ocean. According to some studies, these reliefs must have formed between the Lower Middle and Lower Miocene ages.
This formation is not usually covered with red sediments since they are already present in the Miocene sedimentation. If you come across some of the reddish sediment, it will be only in the first 3 or 4 meters of the hill.
The witness hill must be differentiated from the moors mainly by size. The moors tend to extend throughout the territory and are much higher. Its main difference is that the witness hills are solitary and much smaller. Furthermore, a páramo encompasses an entire ecosystem with a predominance of shrubby vegetation. This causes it to be classified in biogeographical terms as a prairie due to its type of vegetation. However, the witness hill is not categorized as an ecosystem.
I hope that with this information you can learn more about the witness hill.