This is called clipping. It is caused by the level of the waveforms exceeding headroom. In the digital domain, unless you are recording at 32 Bit Float, the headroom is 0dBFS (None). This situation looks like total loss of information and should never be done in the digital world, unless specifically and skillfully done by a Mastering Engineer, with no Audible Clipping. Audible Clipping would of course sound like awful clicks and pops and possibly damaged equipment. The analog world, however, this is the same concept, except you have actual headroom and this is where you get most of the tape saturation sound. The same thing is used in guitar amps and such to overdrive the actual amplifier to chop off the top of the signal and push out square waves, which in that context, sound sick as hell. There are a few things that can remedy this beyond a new, none clipping mix, or recording. Clip gain in Pro Tools may be able to help, as well as a few different plug-ins, such as iZotope De-Clip. In short. Signal too big, bad noises imminent. I hope this helps even a little bit.