GEOLOGICAL HISTORY OF CANAD Essay Example | Topics and Well Written Essays - 1000 words

GEOLOGICAL HISTORY OF CANAD - Essay Example The first class consists of sedimentary  rocks which form the Earths surface. Some consist of fragments that vary in range and are eroded from older  rocks and deposited as gravel, sand or mud and are then consolidated by burial yielding  conglomerate, sandstone or shale respectively. Others comprise of chemical deposits, for example gypsum or rock salt, which resulted from evaporation of seawater. Still others result from biological activities, for instance cemented shell fragments or coral reefs form limestone. Sedimentary  rocks  make  up  the easternmost ranges of the Canadian Cordillera known as the Mackenzie, Rocky and Franklin mountains, but are common in the western Cordillera as well. Many sedimentary rocks  have petrified remains of animals and plants (fossils), and older  rocks  contain diverse kinds of fossils compared to younger  rocks. Igneous  rocks  originated deep within the Earth as molten rock or magma. Magma that solidified deep within the earth formed platonic rock such as granite, which is a common rock particularly in the coast mountains of the western Cordillera and are widely distributed elsewhere. Magma that emerged as lava and cooled at the Earths surface formed a variety of volcanic rock, which is widespread in the interior plateau region and elsewhere in the western Canadian Cordillera. Metamorphic  rocks  formed when igneous  or sedimentary rocks  were buried deep within the Earth during mountain formation. New minerals grew while old features of the rock were destroyed in response to the high temperatures and pressures encountered in the Earth’s core. Consequently, limestone changed to marble, shale to schist, and platonic rock to gneiss. Metamorphic  rocks  are common in the Shuswap Highland, the Coast Mountains and the Columbia, Omineca and Cariboo ranges of the eastern Cordillera. The presence of metamorphic  rocks  at the surface is the evidence of those parts of the