What is the cause of stall and surge in compressor?

stall and surge is caused when the flow in the compressor loses enthalpy and static energy so that it does not have enough power to approach the end of the axis; thus it remains in the annolus of the compressor and creates a stall cell. these cells gradually join each other and create stall zones which are rotating about the axis and are some times called rotating stall. if this stage does not get stopped, the stall cells will cover the whole annolus and will stop the fluid flow through the stages of the compressor and finally lead to surge. if surge happens, the compressor will be out of order.