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 Therefore, it cannot be evaluated on a human scale. The witness hill is the one that reveals the evolution of a stake 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 erosion that has modified the terrain.
In the softer layers of soil, erosion occurs more frequently. Rivers cause erosion and form different hills and other formations, as we can see in the central plateauIf the plateau is eroded on all sides, what is known as a witness hill is formed. These hills have occupied these locations 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 erosional escapes, characterized by a steeper section made of hard rock and a softer section made of soft rock. The harder section is called the cornice, and the softer section is called the slope.
The witness hill has a convex-concave profile and varies depending on the resistance provided by the hard and soft rock layers. When erosion by rivers increases, the witness hill appears flat on all sides. Therefore, they are evidence of a platform that existed in that same place millions of years ago. The remaining relief is a set of hard and soft layers arranged horizontally, which erosion may have sculpted.
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. It has been considered the geographic center of the Iberian Peninsula. Therefore, it holds great importance despite the lack of scientific measurements to support its significance. On the esplanade at the top of this hill is the well-known chapel of Our Lady of the Apostles. It dates back to the XNUMXth century and is a fairly well-preserved monument.
On the slopes of this hill are holm oak pines, playgrounds, a soccer field, trails, and a picnic area. This has made Cerro de los Ángeles a pleasant tourist attraction in close contact with nature. Its base is 610 meters high and it reaches a height of 666 meters. At its highest point is a first-class geodesic vertex. It offers excellent views of Getafe, Madrid, and the surrounding countryside.
Key features
These witness hills can be classified as island mountains. Their main characteristic is that they have 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 lithologyThey are quite useful for geological studies since they are the only ones remaining from other geological formations that previously covered the region. In order to map the evolution of the entire Earth's surface after erosion, it is important to understand the morphology of the relief at that time. This can be determined by the presence of these hills.
These erosion and sedimentation processes are characteristic of our planet's external geodynamics. These witness hills are also characterized by having been surrounded by water, which is why they are located in areas near rivers that have an outlet to the ocean. According to some studies, these reliefs must have formed between the Early Miocene and Early Middle periods.
This formation is not usually covered with red sediments, since they were present in the Miocene sedimentation. If you encounter some of the reddish sediments, It will only be in the first 3 or 4 meters of the hill.
The páramo is distinguished from the páramos primarily by their size. Páramos tend to extend across the territory and are much higher. Their main difference is that the páramo is found alone and is much smaller. Furthermore, a páramo encompasses an entire ecosystem, with a predominance of shrub vegetation. This leads it to be classified biogeographically as a grassland due to its vegetation type. However, the páramo is not categorized as an ecosystem.
I hope that with this information you can learn more about the witness hill.