Dune are ecosystems made up of very fine grains of sand that are developed mainly by the action of winds, forming hills or mountains of different shapes and sizes .
They are extensive dynamic natural barriers that prevent the advance of the sea and also the entry of salt water into the groundwater . In addition, the dunes protect adjacent areas against the erosion process.
We find dunes in deserts and near coastal areas, however, they can be formed by erosion processes of rocks within continents and generally close to riverbeds.
How are Dunes Formed?
The dunes are formed through a complex process resulting from the action of the winds (aeolic dunes) and the sea. They usually appear in places with low rainfall (rainfall) and their expansion occurs slowly and gradually. The main elements of sand dunes are silica, magnetite and quartz. For this reason, it is possible to find dunes of different colors.
This excessive accumulation of sand arises from strong and constant winds in a certain direction and also from the action of high tides, which bring a lot of sand and cannot take it all back. For them to occur, a place of low vegetation with the presence of some barrier is necessary, and that, little by little, constitute piles of sand.
Depending on the variation in winds, the landscape can change over time. Therefore, we conclude that the dunes are ecosystems that are in constant transformation, being able to change their shape, move, decrease or increase. After this formation process, they form peaks (or an immense ridge), where the direction of the winds that formed it is notorious.
dunes of the world
Many dunes are part of the landscape of other countries. The highest dune in the world is Cerro Branco ( Cerro Blanco , in Spanish) which is located in the Nazca Valley in Peru. It has a height of 2,078 meters above sea level. In addition to coastal dunes, there are desert dunes, which are formed in the desert region .
Types of Dunes
According to the movement, the dunes are classified into three types:
- Stationary Dunes : also called fixed or stable dunes, in this case, the dunes do not change their place of origin due to the present vegetation that prevents them from migrating.
- Migratory dunes : also called mobile dunes, these types of dunes change location due to the strong action of winds and the absence of vegetation or a natural barrier that would stabilize them.
- Fossil Dunes : also called paleodunes, this type of formation is older and generally has a more reddish color. They receive this name since they bring together several fragments of prehistoric civilizations.
As for the shape they have, the dunes are classified into five types:
- Linear Dune : these are straighter dunes that form long continuous lines.
- Dune Crescent : also called barchan dune, they are the most common characterized by the half-moon shape they have and also for being wider.
- Parabolic Dune : It has a “u” shape and differs from crescent dunes in that in parabolic dunes the crest points upwards.
- Duna Estrela : they grow more vertically and are named for their pyramidal shape.
- Duna Domo : these are the rarest dunes, characterized by their oval shape and low height.