The basics behind waterfalls are the river comes to a point at the end of the high elevation of land and there is no where else for the water to go other than over the edge of the high point. At the base of the waterfall is layer of very hard rock and beneath that layer is a softer rock, with the pressure of the water coming down over the fall onto the rock it pushes the hard layer down and creates the pool where the water flows into. Over time the waterfall will recede back on itself and this creates what is known as a canyon or a gorge and as time goes by this canyon will get deeper into the underside of the waterfall. There are 10 different classes of waterfall which range from the Class 10 with waterfalls such as Niagara Falls and Khone Falls, Class 9 such as Victoria Falls and down, this classification of the waterfalls is done by the volume of water present on the falls and is a grading system to size the falls.
For many people they assume that the Niagara Falls is the largest of all the waterfalls, however this is not the case, the tallest of all the waterfalls is Angel Falls and this is a whopping 979 metres in height and the Niagara Falls is the worlds most powerful waterfall.