Geography of Newfoundland and Labrador - Geology

Geology

A large part of the island of Newfoundland is an extension of the Appalachian system. Major bays, peninsulas, river systems and mountain ranges are typically oriented southwest to northeast, parallel to the Appalachians.

The eastern part of the island, (the Avalon Peninsula and Burin Peninsula), is mostly folded sedimentary rocks with some intrusions of igneous rock and was part of southwestern Europe or Northern Africa about 250 million years ago. The oldest rocks are Precambrian. Small remnants of Cambrian and Ordovician rocks occur along the coast. Bell Island in Conception Bay is a good example of gently sloping Ordovician sedimentary rock. The plateau in the Avalon Peninsula averages 250 metres (820 ft) above sea level.

The rest of the island is composed of a great variety of Paleozoic rocks of sedimentary, igneous and metamorphic origin. Along the west coast lie the Long Range Mountains, which are formed by an elongated block of the Earth's crust (a horst) which rises to about 600 metres (2,000 ft) above sea level. This part of the island was once part of the eastern margin of continental North America. The island's highest points, the Lewis Hills and Gros Morne are located within this mountain range. To the east is a depression or graben about 30 kilometers (19 mi) wide, which is occupied by Deer Lake and Grand Lake. The main plateau of the central part of the island, which was once the sea bottom of the ancient Iapetus Ocean, has been heavily eroded by water and ice. Steep, solitary rock knobs, called "tolts" in Newfoundland (elsewhere known as inselbergs or monadnocks), which jut 100 metres (330 ft) or more above the generally flat terrain are the remnants of a former higher landscape level. Glaciers which helped shape these tolts left other evidence around Newfoundland. Large blocks of stone called glacial erratics have been left scattered across much of the landscape. The long narrow lakes of the west coast, notably those in Gros Morne National Park resulted from glacial erosion. The lack of good soil on most parts of the island is a result of the scouring effect of glaciers during the most recent ice age. Newfoundland's nickname, "The Rock", is partially a result of the ice ages.

One of the most noteworthy aspects of Newfoundland geology is a result of the constant movement of tectonic plates. Approximately 500 million years ago the action of these plates forced parts of the oceanic crust beneath the Iapetus Ocean up and over the eastern margin of the North American plate. Sections of oceanic crust which overlie continental crust are known as ophiolites. Gros Morne National Park was designated a UNESCO World Heritage Site because it is one of the best places in the world to see the effects of plate tectonics and one of the few places where rocks formed at the Mohorovicic Discontinuity between the crust and the upper mantle of the Earth can be seen.

Another notable geology site is at Mistaken Point, where rocks containing probably the oldest metazoan fossils in North America and the most ancient deep-water marine fossils in the world are found preserved in layers of volcanic ash.

Labrador is the easternmost part of the Canadian Shield and is composed of ancient Precambrian igneous and metamorphic rocks. The interior is averages about 450 metres (1,480 ft) above sea level and is cut by large, east-flowing rivers, such as the Churchill River and its tributaries. The northern coast is largely mountainous. The Torngat Mountains, Kaumajet Mountains and Kiglapait Mountains dominate this area with the highest peak being Mount Caubvick at 1,652 metres (5,420 ft). Torngat Mountains National Park Reserve was created in 2005 to preserve part of this area.