Over the last million years, the alpine region has been subjected to numerous ice ages, which have alternated with relatively warm or mild periods. In this way, morphological evolution has seen the prevalence of processes of ice erosion one moment and river erosion the next. The phenomenon has occurred in such a way that these days, along with typical fluvial morphologies, characteristics of glacial morphology are also often found. This is particularly widespread in the upper zones of the valleys, where fine examples of perfectly preserved glacial cirques can be observed, such as in Cjadinut (Mt. Cadin) and, especially, on the large plateau of Foran dal Muss-Piano di Prevala, which reveals traces of very recent glaciers. Even today, there remains a small strip immediately to the north of the summit of Mt. Canin, as well as a few other small snowfields. This is a very important phenomenon, given that this glacier is one of the few on the Eastern Alps and, above all, that it is located at the lowest altitude. This is due to the concurrence of two decisive factors: the considerable precipitation in the area and its exposure to the north. Numerous glacial valleys, still entirely or almost intact can be found particularly along the northern slopes of the mountain ranges: Mt. Musi and the Lavaruzza high valley. In some cases, there remain traces of glaciers from stadials subsequent to the last glaciation, which have deposited even quite vast arch-shaped moraines. The best preserved of these moraines is located near S. Anna di Carnizza, formed by a small glacier which descended from Mt. Zaiavor. In contrast, fluvial morphology prevails in the lower valley, where erosion has on the whole been extremely severe.

There are numerous examples of deep incised valleys or even gorges, such as those at Rio Nero, Cerni Patok and Venzonassa, in the localities of Stuve to Venzone. Furthermore, within the Park there are some examples of hanging valleys, amongst which Lavaruzza, Cjampeit and Lavarie. These valleys overlook the Tagliamento-Fella plain rising at an altitude of 200-250 m and therefore during periods of fluvial activity they produce a high waterfall. Differences in the depth of watercourses are relatively common and this creates spectacular rapids and waterfalls. Besides those already mentioned, there are other particularly impressive falls, such as the Fontanone Barman, a remarkably powerful Karstic spring, those on the Lavarie river to the west of Plan dai Portolans, on the Lavaruzza at Parés and, finally, along the Rio Nero gorge. Between Mount Cadin and the Cima di Campo peak, there is also a rare example of a fossil valley with river capture.

In the locality of Cjadinut, there is a well preserved old valley head which was heading west. Traces of the valley floor are still visible up to the Malga Campo pasture and are formed of characteristic counterslopes, interspersed with deep transversal incisions eroded by the Cadin, Palalunga and Miniera brooks, which cause the capture phenomenon. The karst morphology is the most widespread and developed on the Foran dal Muss plateau, at the foot of Mt. Canin. Nearly all the karst phenomena are represented here, both above and below ground, constituting a true Karst garden of considerable size: from Bila Pec to Cuel Scláf. These phenomena are particularly intense on the Col delle Erbe and Foran dal Muss, where most of the area’s caves, deeper than 1,000 m, are located.