Why does a waterfall form

We will explore how waterfalls are formed and the processes behind such formations. Waterfalls are magnificent displays of nature and have drawn the attention of people for thousands of years. They are breathtaking examples of the beauty of nature.

Waterfalls are regions where the water flowing suddenly drops either over cliffs or other steep regions. Exactly how are waterfalls formed? It does not happen quickly and the process may take thousands of years. Forming Falls Waterfalls form in rivers that are young. This is due to the channel being deep and narrow to allow for the formation of the waterfall. Generally, waterfalls form in the upper course of a river. This is where a layer of hard rock lies next to a layer of soft rock.

The bedrock, as these layers are collectively known, of a river is the loose sand, soil and silt that sits underneath the river and moves quickly along with the river at steep inclines. This way the plunge pool is formed at the base. The crashing flow also sometimes creates whirlpools that erode the plunge pool beneath them. The erosion at the base of the waterfall causes the water to recede.

The area behind the waterfall is worn away creating a hollow cave like structure that is called the rock shelter. The rocky ledge sends down tumbles and boulders into the stream bed and plunge pools. The waterfall erosion starts again breaking the boulders down of the previous left rocks.

Block waterfall- It descends from a wide stream. Niagara Falls is an example of the same. Cascade Waterfall- It is a waterfall that descends over a series of rock steps. This type of waterfall is safe enough for children to play in the water. Example- Monkey falls. Cataract- It is a dangerous and powerful waterfall. The net result of this action is that the waterfall retreats further upstream to the remaining lip of the hard rock layer. With its high volume of waterfall, Niagara Falls continues to retreat at a whopping rate of about 3 feet per year!

In the adjacent photo, look at the overhanging wall in the photograph, which is further evidence that this process is still going on! The undercutting still continues until you run out of the hard rock layer. At that point, the watercourse will probably go back to being a stream or rapid. Now while these processes highlight the fact that things as seemingly permanent as waterfalls can come and go over time, these same processes also take many, many years to occur.

Heck, even things that took thousands of years to occur are like a blink of an eye in geologic time scales! In any case, I made an attempt at capturing the waterfall formation process in a single drawing to further help you visualize it. Then, insert a board or anything relatively flat and hard with some degree of thickness the thicker the better somewhere into middle of the side of the sand pile.

Finally, pour water onto the slope of the sand pile the same side you inserted the hard, flat item and observe the water flow over the sand and hard object.

If done right, the water should be flowing down the slope of the sand pile eventually cutting into it. Once you accept the idea and science behind the waterfall formation, you might be able to imagine how you can end up with different shapes or types of waterfalls simply by varying the orientation and combination of hard and soft rock with water cutting through them.

Now you may be wondering how all the different rock layers got there in the first place and why these rock layers erode at different rates. Well, just about all of the land you see around you is the result of volcanoes. Volcanoes typically spew out lava, which is really molten rock or rock that is so hot that it acts like a liquid. You can see this action taking place in places like the Big Island of Hawaii, where the lava ultimately solidifies to add to its landmass and become part of the rock layer.

That fact alone illustrates that the rock layers that form from the cooling lava can have differing compositions. And its this differing composition that results in the differing levels of resistance to erosion by water and to a lesser degree wind. Places like the Grand Canyon in Northern Arizona exemplify such geologic episodes as the Colorado River exposed and revealed the many layers of rock holding up the majestic cliffs and buttes. Each layer represents a change in the geologic conditions.

It could be a volcano going off depositing a layer of new lava, or a major event like an asteroid collision depositing a thick soot and dust layer e. The internal heat of the earth also is the engine behind convection, which moves the molten rock beneath the crust. Some of these plates slide against each other, others collide, and still others separate from each other.

There are even hot spots that practically tear heat holes through the crust like the ones that formed the Hawaiian Islands. Soft rock erodes more quickly than hard rock.

Waterfalls are created when the riverbed changes suddenly from hard rock to soft rock. Rapids are formed where a fast-flowing river quickly cuts downward through a bed of hard and soft rocks, eroding the soft rock and leaving the hard rocks standing above the water surface.