Cape Verde's islands fall into two main groups—the Barlavento, or Windward, in the north, which include Santo Antão, São Vicente, Santa Luzia, São Nicolau, Boa Vista, and Sal, and the Sotavento, or Leeward, in the south, which include São Tiago (c.600 sq mi/1,550 sq km, the largest island), Fogo, Maio, and Brava. The islands are mountainous and of volcanic origin; the only active volcano is at the archipelago's highest point, Mt. Fogo, or Cano (c.9,300 ft/2,830 m), which is located on Fogo. Regularly active until the 18th cent., the volcano's most recent eruptions were in 1951 and 1995. The area is sometimes subject to severe droughts and the fierce harmattan wind. About 70% of the population is of mixed African and European descent, and almost 30% are of African descent; there are also a few Portuguese. Most persons are Roman Catholic, and the religion is often mixed with indigenous beliefs. Portuguese and Crioulo, a blend of Portuguese and West African languages, are widely spoken.