As most of us would likely guess, walking is the most popular physical activity in America. But people who walk for exercise do so at wildly varying speeds and intensities. Some stroll at a leisurely 2 miles per hour, which is low-intensity exercise. Others zip along at twice that pace or better, resulting in a sweatier workout.
Mummification is a process in which the skin and flesh of a corpse can be preserved. The process can occur either naturally, or it can be intentional. If it occurs naturally, it is the result of cold (as can be found in a glacier), acid (as can be found in a bog) or dryness.
In geology, petrifaction or petrification is the process by which organic material is converted into a fossil through the replacement of the original material and the filling of the original pore spaces with minerals. common source of silica is volcanic material. Studies have shown that in this process, most of the original organic matter is destroyed. Silicification most often occurs in two environments-either the specimen is buried in sediments of deltas and floodplains or organisms are buried in volcanic ash.