Waterfalls

A waterfall is formed where water flows over a cliff or very steep drop in the river's bed. There are two types of waterfall:
1. Cataracts are found where there are many rapids in a large river. A large volume of water flows down these rapids.
2. Cascade waterfalls have a small volume of water. A series of falls may form one waterfall.

Formation (you will need to know this at GCSE level)

Waterfalls form as a river flows over hard and soft rock. The soft rock erodes more quickly. The river undercuts the hard rock leaving an overhang. The river forms a plunge pool below the waterfall. The water keeps eroding and the waterfall gets bigger. The over-hanging hard rock weakens and falls into the plunge pool. The waterfall retreats, moving upstream. The process begins all over again.
The rock on the top of the waterfall is a hard rock, it is good to give an example such as Limestone.
The rock underneath and behind the waterfall is a soft rock which can be easily worn away. Again, a good example of this is shale.

Some waterfalls are made by glaciers. Waterfalls in Yosemite National Park, for example, formed due to the action of glaciers. During the last ice age, a large glacier in Yosemite Valley was fed by smaller glaciers coming into the side of it. These smaller glaciers carved out smaller valleys. When the weather warmed and the glaciers melted, Yosemite Valley was left with smaller valleys coming into it way up on the sides of the cliffs. Rivers running through these smaller valleys become waterfalls when they enter Yosemite Valley.

Other waterfalls originate where a fault uplifts a mountain range or part of a range, creating a fault scarp over which streams drop steeply. Continued undercutting and erosion of the edge and of the rock bed above the falls move many waterfalls upstream; these ultimately diminish in size, dwindle to rapids, then disappear.

Facts

The tallest waterfall in the world is the Angel Falls (Carrao River, Venezuela). It is 979 metres high.
The highest waterfall in Africa is the Tugela Falls at 947 metres. It is found in South Africa.
Europe's highest waterfall, Utigard in Norway, is 800 metres high.
The Yosemite waterfall (739 metres) is the highest waterfall in the USA.
The Niagara Falls are visited by thousands of tourists each year.

Waterfalls and power

Waterfalls are a natural source of power. Sometimes hydro-electric power stations are built by massive waterfalls. The water is forced to fall down long pipes to the power station below. The force of the water spins wheels which turn the turbines or engines. These turbines generate electricity known as hydro-electric power. A hydro-electric power station has been built by the Niagara Falls to make electricity for the surrounding area.