The Tioga Road, one of the few roads crossing the Sierra Nevada, reaches the highest point of any at Tioga Pass at 9,945 feet and provides a gateway to the park, wilderness, and high country. Winter snow buries the Tioga Road for six to nine months each year, and drifts can reach 30 feet in depth. Road crews begin plowing in April, a process that can take up to three months depending on snow depth, trees and rocks in the snowpack, and 26 potential avalanche zones. Slabs of ice and snow on glacially polished granite make plowing especially hazardous in this area, so rather than plow the precariously perched mass, crews spread charcoal to accelerate melting and sometimes blast unstable ice and snow.