April 28, 2004
The photo above shows a view of the Tablelands in Gros Morne National Park, Newfoundland. With 350-400 cm (140-160 in) of snow and 600-1000 mm (24-40 in) of rain per year, the west coast of Newfoundland can hardly be called a desert, yet the Tablelands stand starkly devoid of trees. The reason lies in the unusual rocks that make up these mountains. The Tablelands are composed of peridotite, which originally formed the mantle beneath the seafloor of the ancient Iapetus Ocean. About 450 million years ago, as Europe and Africa converged with North America, the Iapetus Ocean closed, and a portion of the oceanic crust was thrust onto the eastern edge of the North American continent. Compared to crustal rocks, mantle rocks are enriched in nickel, magnesium, cobalt, iron and chromium. High concentrations of these elements are toxic to most plants. Plant life in the Tablelands is restricted to a few tolerant species and insectivorous plants, such as pitcher plant, which do not depend on the soil for nutrients. The unique opportunity to view the mantle brought to the surface of the earth prompted Unesco to declare Gros Morne a World Heritage Site in 1987.