In geology there are different types of relief. Reliefs that have to do with its composition, its structure or its degree of inclination. In this case, we are going to talk about karst reliefThis is a type of landscape composed of limestone. Limestone is a very special type of rock because, despite being sedimentary in origin, water and living beings give it a coherence that makes it resistant to the various erosive agents that attack sedimentary rocks.

In this article we are going to explain all the characteristics and importance of the karst relief.

Key features

Limestone rock does not fragment but dissolves in water. Therefore, it is resistant to numerous erosion agents except rainwater. Over time, it erodes, forming a solution that creates karst relief. This type of relief develops not only on limestone rocks but also on uvslsTo learn more about karst relief, let's take a closer look at the rock it's made of. Limestone is composed mostly of calcium carbonate. This is what makes it soluble in water; but it's not the only component of the rock. It also contains impurities, and the accumulation of these impurities is called terra rossa. Due to the dissolution of limestone rocks, we can find two types of karst relief: internal and external.

Types of karst relief

External karst relief

The simplest form of dissolution limestone is lapiaz. These are shallow hollows that can range from tiny, millimeter-sized holes to several meters wide. These shallow hollows have a bottom surrounded by ridges, although when they appear on a very steep slope, they take on a more linear appearance, resembling organ pipes. If the lapiaz develops well, it eventually forms a depression in the terrain. This depression generates several types of karst relief:

1. Dolomite. This is a closed depression with a circular or elliptical bottom. It can measure from a few tens of meters to hundreds of meters. The bottom of this relief is covered either by impurities that accumulate in the limestone rock or by accumulated water. As water also accumulates at the bottom, the rate of dissolution of the rock is greater, and therefore, a sinkhole appears, leading to a cave. This bottom is usually funnel-shaped due to the way the limestone gradually dissolves over time. If this formation is close to the coast, it is possible that this resulting bottom has been invaded by the sea, and through saline intrusion, this could further deteriorate the rock.
2. uvala. This type of formation occurs when several sinkholes grow together until they merge into a single depression. It is so named because this coalescence has an alveolar shape. If you want to know more about the sinkholes, this is a good place to start.
3. Polje. This is another type of formation related to karst relief. It occurs when an external depression with a flat bottom and kilometer-long dimensions is closed by steep slopes. It could be said to be a uvala of enormous dimensions. Within a polje, there are smaller karst forms such as uvalas, lapiazes, and dolines. Because these depressions are so large, a hydrographic network often develops over them. Being a closed depression, the waters cannot flow properly; instead, they have a sinkhole that gives access to an underground river. The area near this sinkhole is usually a swampy area, as they usually occur during heavy rains. Everything will depend on the size of the sinkhole and the amount of precipitation. To learn more about this type of relief, you can consult more about the polje.

Internal karst relief

It is another type of karst relief that forms caves. The origin of this type of relief occurs in the underground rivers that circulate inside the limestone rock. This water comes through the sinks that we mentioned above. The rivers take advantage of the weaknesses of the rock to make way through and inside them. If the rock is worn away by the passage of water, it forms different underground paths, allowing us to see authentic underground rivers.

As the river water dissolves the limestone, it abandons its old course inside the cave and continues along its inner course. This is why we can see completely dry caves abandoned by rivers. The most basic form of watercourse we find within a cave is the so-called gallery. These galleries are essential for the water to flow and continue along other paths. The galleries can become more complex and narrow or widen depending on the flow of the water. There are places where the water is forced to rise again and branches into several courses. The area where the water tends to rise again is known as a siphon.

The galleries abandoned by watercourses that begin another course usually maintain high levels of humidity in the walls and circulate water laden with calcium carbonate. These water droplets are what, over the years, will form the stalactites and stalagmitesIf a stalactite joins a stalagmite, they'll form a complete column. For this to form, thousands and thousands of years must pass. That is why caves with these formations are so important.

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Destinations of geological interest

In the dynamics of these galleries, everything can eventually collapse and disappear. This is how gorges and canyons are formed. These are very deep cuts surrounded by vertical walls, closely spaced, and with a river in the background. The area where the river flows from the interior to the exterior is called an upwelling.

I hope that with this information you can learn more about the karst relief.