51. Unlike most of the world’s volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth’s surface; on the contrary, many of them lie deep in the interior of a plate.
　　52. The relative motion of the plates carrying these continents has been constructed in detail, but the motion of the plates with respect to another cannot readily be translated into motion with respect to the earth’s interior.
　　53. Wearing a seat belt saves lives; it reduces your chance of death or serious injury by more than half.
　　54. While warnings are often appropriate and necessary--the dangers of drug interactions, for example--and many are required by state or federal regulations, it isn’t clear that they actually protect the manufacturers and sellers from liability if a customer is injured.
　　55. At the same time, the American Law Institute--a group of judges, lawyers, and academics whose recommendations carry substantial weight--issued new guidelines for tort law stating that companies need not warn customers of obvious dangers or bombard them with a lengthy list of possible ones.