fault line – a potentially disruptive division or an area of contention
fissure – a long, narrow crack or opening in the face of a rock. Fissures are often filled with minerals of a different type from those in the surrounding rock.
fault line. (n.d.). Collins English Dictionary – Complete & Unabridged 10th Edition. Retrieved September 07, 2013,from Dictionary.com website:http://dictionary.reference.com/browse/fault line
fissures. (n.d.). The American Heritage® Science Dictionary. Retrieved September 07, 2013, from Dictionary.com website: http://dictionary.reference.com/browse/fissures