Re: why are the abyssal plains so flat?

The abyssal plains are so flat because the Earth's crust is very old there 
and
has practically no
surface-alternating forces like huge earthquakes, strong currents, or waves.
Over the eons of time,
particles of plankton bodies and dust particles settle very uniformly around
these plains allowing
the surface to be nearly flat.  Is we could see them, they would look like 
the
salt flats on earth.
Les Uhrich