A deep fissure is a long, narrow opening in the earth's surface. The term can be used to describe a variety of geological features, including chasms (5 letters), crevasses (8 letters), abysses (5 letters), gashes (4 letters), slits (4 letters), crevices (7 letters), rifts (4 letters), and rents (4 letters). These features are typically formed by tectonic activity, erosion, or other natural processes.