The crossword solution for the term CRACK IN THE CRUST is FAULT. This term is used to describe a fracture or break in the Earth's crust, which is the outermost layer of the planet. It is caused by tectonic forces, such as earthquakes, volcanic activity, and other geological events. The crack can be visible on the surface or hidden beneath the ground. FAULT lines are often studied by geologists to better understand the Earth's structure and history.