The island chain is of volcanic origin. Fogo has the only active volcano, Pico do Cano (Mount Fogo), which reaches 2,829 m (9,281 ft) above sea level. Peaks on Santo Antão and São Tiago reach 1,979 m (6,493 ft) and 1,392 m (4,567 ft), respectively. All but three of the islands are quite mountainous, with prominent cliffs and deep ravines. High ground and southwestern slopes support lush vegetation because of moisture condensation. Only four islands have year-round running streams. Mindelo on São Vicente is the principal port, but there are several other fine harbors.