Our planet is called the “blue planet” because it appears that way in satellite photos. It is the large bodies of water, the hydrosphere, that give this colour to the planet we are part of. Water is the most abundant component in all living things that inhabit the planet, from the smallest microorganisms to large mammals and the immense plant world.
This precious element reaches all species that inhabit the Earth through what is called the “hydrological cycle,” consisting of water’s passage through its three physical states: gaseous, liquid, and solid (image 1).
From “Following the Current” by A. Lacci and G. Baldaccini. Drawing by Rossella Faleni.
Water, as we experience daily, exists simultaneously in its three forms. Following it on its perpetual journey, we note that besides its essential role as a source of life, it also acts as a “sculptor” of landscapes.
It falls to the ground, forming streams that join other streams, becoming rushing torrents and then rivers that flow down from mountains or hills, gradually slowing until they bog down at their mouths and finally reach the sea.
Following this path, we can find ourselves in the canyons typical of “Western” landscapes or in the gorges called orridi in Italy. In any case, we are witnessing the millennia-old work of a stream or river. (Image 2)
The Latins used to say “gutta cavat lapidem” meaning “a drop of water hollows the stone,” precisely because, over the years, even the hardest stone can be smoothed and carved by water. The speed at which this phenomenon occurs is proportional to the strength of the current and the solubility of the rock. Often, layers of more or less “soft” rock alternate: these are the cases in which water creates sculptures with unique shapes.
As rocks erode, they enrich the water with minerals. This means that each watercourse acquires unique chemical characteristics that influence the development of flora and, consequently, fauna within the same river habitat and in neighboring areas, creating distinctive and unique ecosystems.
The steep slopes, which make the current highly erosive in its initial course, also facilitate the transport of pebbles, mud, and debris. In the downstream reaches, the current’s effect is no longer erosive but alluvial, and the material transported downstream accumulates, favouring the formation of valleys and fertile plains in the middle stretch and of islets, ridges, or barriers in the final stretch. (Image 3)
The river mouth is the final point where materials transported by the river accumulate; it is the junction between the freshwater of the river and the saltwater of the sea, between the river current, which flows continuously perpendicular to the coastline, and the rhythmic motion of the sea waves. The meeting of these very different water masses creates a series of physical events that shape the landscape and ecology of this transitional environment. If the river is recently formed (considering geological timescales!), there has not yet been accumulation of materials in the final stretch; therefore, the river enters the sea in an almost straight line. Since the current is not strong in the final stretch, the sea, with its alternating tides, tends to enter the final stretch, widening it into a funnel shape. This type of river mouth is called an estuary.
As time passes, the river continues to transport materials, which, thanks also to the wave motion, which counteracts the tendency of the materials to continue their journey, accumulate in the estuary area. Small islands begin to form. The river water now reaches the sea through multiple routes, causing the mouth to further widen, taking on the shape of a delta. (Image 4).
As this process continues, ridges of land begin to form in the sea. Over time, they tend to close off the mouth area, creating a lagoon. However, the river continues to carry earth, sand, and stones, and the partially filled lagoon becomes a wetland behind the dunes. These types of marshes are very important for migratory animals and are areas of great natural interest. Until a few centuries ago, they were widespread in Italy, but land reclamation has caused their near-total disappearance.
The transformative effect of flowing water is not limited to surface waters; those that form underground aquifers also often create beautiful, imaginative sculptures. We are referring to the formations that adorn caves found in limestone areas. As water seeps in, it dissolves the minerals contained in the rocks; the mineral-laden drops, falling for millennia in the same spot (dripping), give rise to stalactites and stalagmites (Image 5).
We can therefore affirm that flowing waters constitute one of the most important natural shaping forces due to their ability to transform, over the course of millennia, the physiognomy of terrestrial landscapes.
Credits
Author: Anna Lacci is a science communicator and expert in environmental education, sustainability, and place-based teaching. She is the author of documentaries, nature books, workbooks, interdisciplinary teaching resources, and multimedia informational materials.
Translated by Maria Antonietta Sessa
