Rescuers resumed drilling on Wednesday to ventilate toxic gas blocking their attempt to reach four workers still trapped in a West Virginia mine—though the process could take days. Monday’s explosion was “very violent,” a company executive said Tuesday, so the 25 miners who died had little chance for survival. Joan Quigley, author of The Day The Earth Caved In: An American Mining Tragedy, talks to mining experts about the factors that still make mine safety an elusive quest. Plus, our gallery of mining disasters and rescues.