The source of the Cetina River in Croatia is like "the eyes of the earth". How did this scene come into being?

What is the source of the Setina River in Croatia? Eye of the earth? It is very beautiful. The formation of this scene requires three conditions: 1, there is a big lake next to it, 2, there is a pipeline between the lake and the source, and 3, the wall of the source must be lava rock.

1. First, there is a big lake next to it.

This is the most critical, because if there is no large lake nearby to provide water, it is expected that the water at the source of the so-called Eye of the Earth will have dried up long ago, and the source called Eye of the Earth is next to Sapphire Lake, which is one of the top ten lakes in Eastern Europe. Therefore, the sapphire lake can continuously supply water to the eye of the earth, so that the eye of the earth will not dry up.

2. The lake communicates with the source.

If the lake is completely isolated from the source, water cannot be transported. For example, if the bottom of sapphire lake is sealed shale, the eye of the earth will dry up. According to scientists' research, the bottom of Sapphire Lake is relatively loose, and water can be smoothly transported to the source of the Eye of the Earth through cracks or relatively large pipelines. And the filtered water passing through the pipeline is clear. Only in this way can we see the bottom clearly, not to mention that the eye of the earth is very deep, tens of meters deep, and there can be no pollution if we want to see the bottom clearly.

The lake wall of the eye of the earth must be lava.

That's because volcanic rocks have a porous structure, similar to graphite, and have adsorption. In this way, algae and other things in the eyes of the earth can be adsorbed on lava rocks to prevent them from spreading in the eyes of the earth and affecting the vision. This is easy to understand. If the water quality is polluted, it will not have the effect of the eye of the earth. To have the effect of the eye of the earth, the most basic thing is to have clear water quality. Other rocks rarely have this effect, so in order to absorb algae and make the water clear, the lake wall must be lava rock.