How are Waterfalls Formed

Waterfalls are a type of landform, usually in the form of streams (having stream bed and banks) that flow from a height or down a slope, such as water flowing from steep cliffs or precipices. The water source of waterfalls varies, based upon the origin. For example, the water sources can be glaciers, rivers, streams and even creeks. It is a fact that two of the fifteen largest waterfalls are glacier fed; whereas, majority of the remaining have their sources in rivers.

Waterfalls occur in each and every continent, except in Antarctica. The Angel Falls, located in Venezuela (South America) is the largest waterfall in the world, with its height measuring 979 meters (3,212 feet). In terms of numbers, Norway leads the list with five of the largest waterfalls.

How are Waterfalls Formed

The explanation as to what makes a waterfall is controversial among the waterfall lovers of the world. The commonly accepted answer is that a watercourse (any stream, river or creek) that falls from a height of at least three meters (around 10 feet), having a slope of 30 degrees is a waterfall.

Waterfalls are formed due to natural processes. However, waterfalls can also be man-made water bodies such as garden waterfalls and waterfalls created by dams and hydro-electric power stations. These man-made waterfalls often have a minimum vertical height of five feet and water is present throughout the year. Let' take a look on how waterfalls are formed due to natural processes.

As per geology, waterfalls are formed due to the erosive activity of the watercourse, flowing over varied layers of rocks that have different rates of erosion. Let's discuss about two consequences of erosion; a watercourse traversing over a soft rock layer will have higher rate of erosion, in comparison to another area with a hard rock layer. Over a period of time, the erosion process further continues to erode the soft rocks, resulting in the steepening of the watercourse beyond the layer of hard rocks.

In such a condition, the soil erosion rate is also accelerated due to steepening effect and increased speed of the watercourse. Eventually, the steepness of the watercourse increases and a stage comes in which the slope becomes almost vertical and/or totally vertical, leading to the formation of waterfalls. The base where the waterfall lands, is called a plunge pool.

The height of the waterfall increases, as the watercourse continues to cut the soft rocks. It is also observed that the soft rock layer directly under the hard rocks is undercut. In some cases, the watercourse does not have contact with the wall of the cliff. The overhanging hard rock becomes unstable due to undercutting process, whereby it may collapse and retreat back.

What are the Types of Waterfalls

Waterfalls are categorized into several types, based on the course of waterfalls, amount of flowing water and most importantly, the geological process that creates the waterfall. The two most common types of waterfalls are cascade and cataracts. Cascade waterfalls are formed, if the volume of water is less and when there are many irregular or uneven surfaces underneath the surface of water; whereas, larger waterfalls with more volume of water, usually associated with rapids are called cataract waterfalls. Based on the features, waterfalls can be ledge falls, slide falls, parallel falls, staircase falls and combination falls.