The Ring of Fire.
Its called the ring of fire because of all volcanic activity surrounding the Pacific Ocean.
One way in which the study of populations ( human populations - I assume) affects us is that they can help predict the population size in the future and prepare us for it. For example, if we see that the population is decreasing, a country might want to consider supporting child-bearing or immigration to avoid the problem of too many people receiving pensions but not paying taxes.
A cliff is a rock exposure with a near vertical (or is vertical) facing. An escarpment is a long cliff, or steep slope. (causes faulting processes)
