| Rainmaker Mountain | |
| Elevation M: | 523 |
| Location: | Tutuila Island in American Samoa |
| Coordinates: | -14.2764°N -170.6528°W |
Rainmaker Mountain (also known as Mount Pioa[1] [2]) is the name of a mountain located near Pago Pago, American Samoa on Tutuila Island. Rainmaker Mountain traps rain clouds and gives Pago Pago the highest annual rainfall of any harbor. [3] [4] [5] The average annual rainfall on the mountain is around 200inches.[6] It has a three-pronged summit. Rainmaker Mountain and its base were designated a National Natural Landmark in 1972 due to the slopes’ tropical vegetation.[7] [8]
Rainmaker Mountain is one of several giant volcanic mountains that created Tutuila Island. It dominates the scene from nearly every point in Pago Pago Harbor. It comprises three mountain peaks: North Pioa, South Pioa, and Sinapioa. The peaks range in elevation from to . The 170acres designated landmark area occurs above the 800acres contour line. Several endemic species are present only here and on Matafao Peak, the highest point on Tutuila.[9]
Rainmaker Mountain, famous in Samoan legend and lore, is also geologically important as an example of a volcanic plug (quartz trachyte). The upper slopes are montane rainforest and the crest is montane scrub.[10]
A closeup of the mountain is visible up Rainmaker Pass.[11]
Rainmaker Hotel was a hotel at the port entrance under the mountain.[12]
The mountain is a volcanic feature known as a trachyte plug, a volcanic intrusion made of extrusive igneous rocks having alkali feldspar and minor mafic minerals as the main components and a fine-grained, generally porphyritic texture.
Rainmaker Mountain is home to rare plant species that have been documented only once or twice within the Samoan Islands. These include Zschaemum cf. byrone, a grass species, and Mapania vitiensis, a sedge, both of which were found in the montane scrub habitat of the mountain. Additionally, the fern Dipteris, characterized by leaves that resemble those of Tacca, is another rare species recorded in the region. In the Samoan Islands, Dipteris has been observed exclusively on Rainmaker Mountain and Matafoa Mountain, highlighting the ecological significance of these National Natural Landmarks.[13] [14]
Petrels and shearwaters are known to breed predominantly on the higher elevations of Tutuila, with Rainmaker Mountain serving as a particularly significant habitat. These seabirds are rarely observed near the coastline.[15] Rainmaker Mountain is a nesting site for both the Wedge-tailed Shearwater and the White-throated Storm Petrel. The Wedge-tailed Shearwater, a rare species in American Samoa, likely burrows in the mountain's high-altitude soil. It is also thought to inhabit the cliffs and inaccessible montane scrub of the mountain.[16] [17]
In 2023, a groundbreaking discovery was reported: researchers from Archipelago Research and Conservation (ARC), in collaboration with USFWS, DMWR, and NPS, identified four active burrows of the rare Tahiti Petrel on Rainmaker Mountain and Matafao Mountain. This marked the first confirmed breeding activity of the species on Tutuila in nearly 40 years. Additionally, researchers documented new colonies of the Tropical Shearwater.[18] [19]