Its terrain includes numerous hills rising more than 183 meters (600 ft.), formed by
Holocene volcanic eruptions overlying a preexisting barrier reef. Much of the island's industry and population are concentrated on the plain's relatively flat areas.
Pago Pago International Airport occupies a low-lying section in the southeast, where rainfall averages approximately 118 inches per year. Between 1970 and 2004, annual precipitation at the airport varied by as much as 46 inches above average (in 1981) and 61 inches below average during the
1997–98 El Niño event. Urbanization—consisting of low buildings and paved roads—occurs primarily in the eastern portion near the airport. Located on Tutuila Island's southwestern coast, the Tafuna-Leone Plain exhibits the island's gentlest
topography, featuring approximately 200 meters of relief. The landscape formed during the Holocene, when volcanic eruptions buried portions of an older barrier reef. ==References==