Rainmaker Mountain and its base were designated a National Natural Landmark in 1972 due to the slopes’ tropical vegetation.

[10] Rainmaker Mountain, famous in Samoan legend and lore, is also geologically important as an example of a volcanic plug (quartz trachyte).

The mountain is characterized by its composition, which includes rhyolite that is low in quartz, as well as zones in contact with basaltic flows.

The dome is primarily formed from basaltic fragments and explosion breccias, with occasional inclusions of trachyte or rhyolite blocks.

It is classified as an endogenous dome, which formed through the upward push of magma into a narrow vent roughly 1.25 miles (2 kilometers) in diameter.

The summit features a cratered pumice cone, which formed when pasty lava erupted and partially filled the area.

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.

[17][18] Petrels and shearwaters are known to breed predominantly on the higher elevations of Tutuila, with Rainmaker Mountain serving as a particularly significant habitat.