Others are so-called "self-healing" minefields which can detect when a gap in the field has been created and will direct its mines to reposition themselves to eliminate that gap, making it much more difficult and dangerous to create a safe path through the minefield.
Various minefields include "self-repair" varieties capable of detecting gaps in the field and adjusting their mines to close those openings, thereby making it more difficult and dangerous to create an unmineaded path.