Mangaia, the island farthest south in the Cook archipelago, lies no miles southeast of Rarotonga. Marshall (16, p. 1)* records its position, its circumference as 17.62 miles. Its area is estimated as 17,500 acres (26, p. 361).
In the absence of a complete official map, Marshall (16, pl. 1) made a reconnaissance of the whole island in 1923. He was assisted by his native guide, Mama Akaui, who knew the localities on the western side of the island, but some of the information given by him for other parts is inaccurate. His greatest lapse is the omission of the district of Karanga, which lies between the districts of Tavaenga and Ivirua, and completes what are known as the "six districts" (puna) of Mangaia. This subject was thrashed out with me on the slopes of Karanga by a group of old men with Marshall's map before them. They indicated the boundaries of Tavaenga and Karanga as shown on the readjusted map (fig. 1).
As the physical features of the island have had a marked influence on the culture of the people, Marshall's physiographic outline (16, p. 7) is quoted:
The island is surrounded by a coral reef, which in most places has a width of not more than 300 feet; at one place its width is nearly 1,000 feet. From the inner side of the reef platform the coast rises abruptly to a height of 10 to 30 feet and continues as a gentle and more or less uniform slope, which rises 20 feet in a distance of about 600 feet. From the inner edge of the slope a cliff 65 feet high rises abruptly, forming a wall which may be climbed at very few places. Extending inward from the top of the cliff is a broad surface, from which project innumerable sharp limestone pinnacles, when travel is impracticable except where paths have been made. This raised platform of eroded coral rock is called the Makatea; a little more than a half mile from the coast its surface stands about 200 feet above sea level. At its inner edge, the Makatea is terminated by a steep cliff which descends 150 feet or more—in places almost to sea level—and which is unscalable for the greater part of the circumference of the island. At the foot of this inward-facing escarpment lie extensive swamps which receive all the run-off from the central part of the island. The swamps are drained by subterranean channels passing to the sea through the Makatea at depths of more than 150 feet. The central part of the island is a dissected mass of volcanic rock which rises gradually to a height of 554 feet above sea level. Generally this igneous core is separated from the Makatea by the moat which contains the swamp, but in a few places projecting spurs extend downward to the Makatea platform. The summit of the island is a flat surface three quarters of a mile long and less than a quarter of a mile wide. The central point of this flat is called Rangimotia, the "Crown of Mangaia."
The fringing reef which surrounds Mangaia has, according to Marshall (16, p. 10), a raised "Lithothamnion ridge" 60 to 90 feet wide. The seaward edge, exposed to a height of about 2 feet at low water, is explored by women-folk for shellfish and echini. Deep chasms, varying in width and depth, page break page 5penetrate the rim. Where they cross the rim, they form channels (ava), which are useful for launching small canoes. The channels, however, do not penetrate far, and none of them reach the shore. An attempt has been made at Oneroa to enlarge and lengthen one of these ava to provide a boat passage to the shore. The lack of suitable natural passages has affected the method of launching and beaching canoes.
From the inner side of the raised outer border of the reef there is a sudden downward slope of 2 or 3 feet. The reef flat, which extends from here to the shore, ranges from 80 to 300 yards wide; its surface is always below low-water level. The flat is covered at high tide. The stretch of water between the raised rim and the shore is usually alluded to as the "lagoon." Depressions pitted in the uneven flat form pools when the tide recedes. Some pools are fairly large and are frequented by fish which come in and out with the tides.
The reef flat is bordered inland by a "terrace slope" 300 to 600 feet wide. Before the advent of Christianity the terrace slope was not permanently occupied, but the national marae of Orongo is located on the terrace and at times the Shore High Priest of Rongo took up his residence near the marae. Two divisions of the village of Oneroa are now located on the terrace. Coconuts have been planted all along the coast.
The makatea is penetrated by many crevices and caves which once gave refuge to fugitives after battles. It is probable that some tribes would have been exterminated but for the concealment thus provided. Access to the coast was by steps up the inner and outer faces of the makatea connected by narrow winding paths that avoided the pinnacles and crevices. Plants grow in the red friable soil between the pinnacles. Taro flats form the puna lands over which so much fighting took place. Marshall (16, p. 35) states:
The taro flats are about 40 feet above sea level, where the streams that supply the water to them issue from the valleys. They descend by a series of artificial terraces and end about 20 feet above sea level at the base of the makatea wall. Here the water enters a sink, which may be as much as 10 feet below the general surface, and passes in channels through the makatea, finally issuing on the inner side of the reef flat in the form of springs.
The volcanic slopes in the center of the island are covered with fern (Gleichenia) and support groves of toa (Casuarina). The stream valleys have dense thickets of small trees and shrubs. The whole central region, referred to as "the mountain" (maunga), gave cover to fugitives belonging to defeated tribes.