Shockwaves & Flow breakaway

[Pint o' Pale]

Hello All.

I am after an explanation as to why there is a flow separation/turbulence behind a shockwave. From texts I am reading (Kermode) and searching this site, I understand that at the shockwave there is a increase in pressure and density, however no reason given as to why the flow then separates behind the shockwave.

Is it caused by the adverse pressure gradient over the upper sfc of the wing ie. air trying to flow from high pressure to low pressure? Does this still occur with the associated increase in pressure at the shockwave?

Thanks for your help in advance.

[TURIN]

My understanding was that the shock wave itself caused turbulence. Result, separation and in some cases shock stall.

I could be wrong though.