Although volcanism and erosion are the chief factors in the growth and erosion of a volcano, other factors are also involved. Subsidence is known to occur. Changes in sea level, occurring mostly during the Pleistocene, have caused drastic changes; an example is the breakup of Maui Nui, initially a seven-volcano island, which was transformed into five islands as a result of subsidence. High rainfall due to the trade wind effect impacts on the severity of erosion on many of the major volcanoes. Coastline collapses, a notable part of the history of many of the Hawaiian volcanoes, are often devastating and destroy large parts of the volcanoes.