Succession is a core concept in the field of ecology. Succession is the process by which a given ecosystem recovers its composition of species after a disturbance, such as a flood, fire, or earthquake. One commonly used example of this is the recovery of the ecosystem after the 1980 eruption of Mt. St. Helens. Generally after a disturbance, the first species to re-establish themselves will be species referred to as "R-selected". These species generally have short generation times and produce large quantities of young, of which only a few may survive to adulthood. These traits make these species suited to colonize an area such as one that has recently suffered a disturbance. Once a population of R-selected species exists in an area, they will modify the environment, either enabling or inhibiting the further colonization of other species. Eventually the ecosystem will move from being dominated by R-selected species to being dominated by a "climax community" of K-selected species, which generally have longer generations, fewer young, but are able to utilize a given set of resources more efficiently.