Sugarloaf Mountain, Rio de Janeiro

Sugarloaf Mountain, or Pao de Acucar, is a granite and gneiss peak rising about 396 meters directly from the water's edge at the mouth of Guanabara Bay in Rio de Janeiro, Brazil, formed from a body of igneous rock that intruded deep in the crust roughly 600 million years ago during a period of continental collision. Over hundreds of millions of years, softer surrounding metamorphic rock eroded away while the more resistant granite-gneiss body remained, and its smooth, rounded profile is a classic example of exfoliation, in which sheets of rock progressively peel away from the surface of the dome as pressure from long-buried rock is gradually released. Its distinctive shape, said to resemble a traditional loaf of refined sugar, has made it, along with the nearby Corcovado peak, one of the defining granite landmarks of Rio de Janeiro's coastline.