Why are there sharp rocks at the bottom of a waterfall?

Question

I mean, shouldn't it be the opposite? Shouldn't the tumbling waves slowly weather down the rocks?

Answer 1

They are sharp, angular rocks because they fell from the edge of the waterfall where the water undercuts the lip of the falls and the unsupported rocks tumble to the bottom where they will eventually become rounded by the water.

Answer 2

If the water is weathering down the rocks, don't you think that sometimes the weathering can form sharp edges??  Like when someone sharpens a knife, they are wittling away the thicker edges into thinner ones.  The waves are doing the same thing and waterfalls are not smooth flowing so the rocks become jagged from the weathering.

See?

Answer 3

The jagged rocks at the base come from immediately above.  They haven't had time to move or wear down much.  If you go downstream, you will find that the rocks become progressivley more rounded.

And actually, in some places the rocks at the base of a waterfall ARE quite rounded.  You see this more in mountain streams where igneous rock types are dominant.  They start out more rounded and a lot of the rocks are accumulated at the base of the waterfall after rolling down from upstream.

Answer 4

Physics, we wonder because we can. We also dwell and hope because this is what we do. Questions are abundant and worthwhile. I hope you find the answer to yours.  I do love starfish in the ocean and seashells too.!!!! Used to bring home a few shells. Where are they today?

In California we are calling it being blue.