Waterfalls 16 Month 2012 Calendar. A waterfall is a geological formation which usually results from water, which flows over an erosion-resistant rock formation which eventually suffers a sudden break in elevation. Some waterfalls form in mountainous environments where erosion is rapid. Sometimes, rather than the result of many years of geological erosion, the waterfall could be the result of a relatively sudden geological process, for example a landslide or volcanic activity. Whether created through natural erosion or sudden geological activity, these beautiful pictures show the diversity of waterfalls and the rivers or streams immense power when carving its path to the sea! This calendar features 13 full colour photographs alongside a detailed calendar grid with room to record special dates and appointments.