The Blue Mountain Range consists of layers of metamorphic and igneous rocks, which contain iron ore deposits. The rocks in the Rio Grande Valley carry some copper deposits, while in the Marshall Hall area, high-grade manganese ore may be found.
Blue Mountain has the highest peak in the island. The walk up is a popular trek for the adventurous that seeks the unsurpassed beauty afforded at this elevation. Portland shares the crest of the Blue Mountain peak with St. Thomas at a height of 2,256m above sea level. The Blue Mountain East Peak reaches 2,248m above sea level and a few other points strive to match those heights along the Blue Mountain range: These include Sir John’s Peak at 1,930m above sea level and Portland Gap at a height of 1,675m above sea level.
Portland lies in the direct path of the prevailing northeast trade winds that bring rain, and its hilly features conspire to trap the winds and ensure almost daily rainfall.