A

David

Darling

waterfall

Bridal Veil Falls, Yosemite.

Fig 1. Bridal Veil Falls, Yosemite.


Waterfalls and pools are both caused by hard bands of rock spanning the river bed.

Fig 2. Waterfalls and pools are both caused by hard bands of rock spanning the river bed.


A waterfall is a vertical fall of water where a river flows from hard rock to one more easily eroded (see erosion), or where there has been a rise of the land relative to sea level or blockage of a river by a landslide. The largest waterfall in the world is one of the Angel Falls, Venezuela (815 m).

 

Water flowing over a hard bed erodes the softer beds below, causing a waterfall with a plunge pool beneath 9fig 2). Over time, erosion causes the face of the waterfall to retreat, leaving a gorge downstream of it. Niagar Falls is formed from a hard bed of nearly level rock and has a gorge 10.4 km (6.5 miles) long below it.