A WATERFALL is a vertical step in the river. It is usually found along the upper course of the river where velocity is usually greater. Waterfalls usually form when there is a band of more resistant rock cutting across less resistant rock, as seen in the picture below (:
As the river flows, the more resistant rock gets eroded slower than the less resistant rock. Thus, a step is formed. Over time, as water goes down the vertical step its kinetic energy hits the bottom, causing a deep pool under the waterfall. This is called the PLUNGE POOL.
As the plunge pool gets larger and larger, the overhang of the waterfall (the more resistant rock, in the picture) will eventually drop into the plungepool due to a lack of support. Overtime, the waterfall receeds. Apparently, the niagara falls retreats about three feet a year! :O
The biggest waterfalls in the world attract many tourists. These include niagara falls, victoria falls etc. Here's a pic of the picturesque Niagara Falls (:
Grace.
Niagara falls are beautiful!!
ReplyDeleteBut it could have been more interesting if we can know whether it's formed by the fault mechanism or it is because it flows from a band of resistant rock to less resistant tock.
commented by cao li
yup, i agree, that is why it is important to the land must have a gradient that consists of more and less resistant rock for the formation of a waterfall to occur.
ReplyDeletejia min
Hey grace i think you made an awesome post with the relelvant example of the niagara falls and also with the use of the photo of waterfall formations. And it is quite easy to understand what you mean as you have explained waterfalls well.
ReplyDeleteSubha(:
It's really surprising to know that waterfall actually retreats constantly at a gradual pace. I wonder what will happen when a waterfall actually retreats into a urban area. :O
ReplyDeleteBut you forgot to mention a point, where the unsupported rocks falls into the plunge pool, preventing the plunge pool depth from getting deeper and deeper each year. :)
Luke