Hualalai volcano, at the western end of the island, is the third youngest shield volcano on Hawaii.  At 2523 m, it is dwarfed by its massive neighbors, Mauna Loa and Mauna Kea.  Three rift zones, dotted with cinder cones and spatter cones, trend north, NW, and SE, and converge about 5 km east of the summit.  Detailed mapping has shown that 95% of the surface area of the basaltic shield volcano is of Holocene age, more than half is less than 3000 years old, and a quarter is less than 1000 years old.  The only historical eruptions of Hualalai took place during the end of the 18th century and in 1801, when lava flows from vents on the NW rift zone reached the sea and buried Hawaiian villages; the 1801 Huehue lava flow underlies part of the international airport at Kona.  The earlier of the two flows, the Kaupulehu lava flow, is notable for its large quantities of lava-encrusted mafic and ultramafic nodular xenoliths.