Fault lines are fractures in the Earth's crust that can cause earthquakes, volcanic eruptions, and other geological events. The four crossword solutions for the term 'fault line' are 'OOPS' (4 letters), 'IGOOFED' (7 letters), 'MEACULPA' (8 letters), and 'ITSNOTYOUITSME' (14 letters). All of these terms are expressions of regret or apology, which could be used to describe the consequences of a fault line.