【Gulf】 , 【chasm】 ,  【abysm】 ,  【abyss】 basically denote a hollow place of vast width and depth in the earth.

【Gulf】  and  【chasm】  suggest a depth which, though vast, is still measurable;  【abysm】  and  【abyss】  suggest immeasurable depth.

【Gulf】 is the most general term and may properly be used of any wide and deep hollow place. In its extended use  【gulf】 suggests separation by a great, often unbridgeable distance.

【Chasm】 adds the implication of a deep and sometimes wide breach in a formerly solid surface. In extended use  【chasm】 still stresses a sharp break in continuity.

【Abysm】  and  【abyss】 may designate the bottomless 【gulf】 or cavity of ancient cosmogonies and both have been applied to hell when thought of as a bottomless pit; in other applications they usually connote not only fathomlessness but also darkness and horror.

【Abysm】 is somewhat old-fashioned.

【Abyss】 is commoner in general modern use and, like  【abysm】 , it carries over into its extended uses the notion of vast, immeasurable void.