The most common directly preserved fossils are unaltered hard parts of a living organism, like shells, teeth, and bones. ... After the remains of an organism have been buried and cemented within sediment, water percolating through the sediment leaches out the fossil. This leaves a cavity in the rock, called a mold.
Krakauer<span> is hoping to find clues that will help explain why Chris stayed on the </span>bus<span> rather than finding a way to save himself.</span>
