The surface of the upper slopes of Mauna Loa is almost wholly of two widely different kinds of barren lava-flows, called by the Hawaiians the pahoehoe and the aa.
The adult stage of this form is the Filaria loa found in the subcutaneous tissues of the limbs.
Mauna Loa (" Great Mountain "), on the S., is by far the largest volcano in the world; from a base measuring at sea-level about 75 m.
Of Mauna Loa, and blending with it in an intervening plateau, is Mauna Kea (" White Mountain," so named from the snow on its summit), with a much smaller base but with steeper slopes and a crowning cinder cone 13,823 ft.
Above the sea, the maximum height in the Pacific Ocean; blending with Mauna Loa on the N.N.W.
Mauna Loa and Kilauea are still active.
Cinder cones are the predominant type of craters on both Mauna Kea and the Kohala Mountains, and they are also numerous on the upper slopes of Mauna Hualalai; but the more typically Hawaiian pit or engulfment craters also abound on Mauna Hualalai and Mokuaweoweo, crowning the summit of Mauna Loa, as well as Kilauea, to the S.E.
Formerly, on the eve of a great eruption of Mauna Loa, this crater often spouted forth great columns of flame and emitted clouds of vapour, but in modern times this action has usually been followed by a fracture of the mountain side from the summit down to a point moo ft.
The first recorded eruption of Mauna Loa was in 1832; since then there have been eruptions in 1851, 1852, 1855, 1859, 1868, 1880-1881, 1887, 1896,1899 and 1907.
But the eruptions of Mauna Loa have consisted mainly in the quiet discharge of enormous flows of lava: in 1859 the lava-stream, which began to run on the 23rd of January, flowed N.W., reached the sea, 33 m.
Another curious feature of Mauna Loa, and to some extent of other Hawaiian volcanoes, is the great number of caves, some of them as much as 60 to 80 ft.
About io m., where it culminates in the round-topped hill of Mauna Loa, 1382 ft.
The mamo (Drepanis pacifica) has large golden feathers on its back; it is now very rare, and is seldom found except on Mauna Loa, Hawaii, about 4000 ft.
The principal rivers of this region are Sama (which forms the provisional boundary line with Peru), Tacna, Camarones, Loa, Copiapo, Huasco, Elqui, Limari and Choapa.
The Loa is the largest, having its sources on the slopes of the Cordillera south of the Minho volcano, between 21° and 21° 30' S.