View from Melville Lookout

Melville Lookout rewards a hiker with one of the best views from Birch Brook Nordic Ski Club trails.

About six hundred feet below is Gosling Lake, site of the annual Labrador Canoe Regatta. A brook joins Gosling Lake to Lake Melville, an inland arm of the Atlantic Ocean. The Mealy Mountains, part of a proposed National Park region, provide a snow-capped border along Lake Melville. Happy Valley - Goose Bay is to the southeast. A large sandy plateau which hosts the airport and much of the town was an exciting discovery to the engineers seeking a suitable location for launching trans-Atlantic flights during World War Two. Wetlands frequented by moose and waterfowl follow the northeast shore of Lake Melville. Behind to the west, rolling hills, the highest about seven hundred feet, extend towards McLean Lake and the end of Birch Brook trail system. All around, rock outcrops and random boulders lie exposed by the 1985 forest fire which locally burnt 40,000 hectares but secondary sucession is actively underway.

view from Melville Lookout

Geology

Earth Scientists explain major geological features of the region in terms of plate tectonics and the more local landscape appearance as a result of glaciation. The present configuration of continents is a rather recent arrangement by geological standards, which measures time in millions and even billions of years. The Earth's crust is divided into rigid plates which move about the surface driven by convection currants in the underlying mantle. At distant times in the past, various continents have formed, split apart, and sections have moved elsewhere and measureable movements of our present continents in centimeters per year continue. Crustal movements explain Lake Melville and the Churchill River Valley.

Plate Tetonics

By early Archean times (3800 to 3400 million years ago), the North American Precambrian Shield consisted of a cluster of continental nuclei. Each collision and joining of another section of continental crust caused an orogeny, an episode of mountain building accompanied by intense rock deformation. Sedimentary and igneous rock were folded and faulted along the plate margins while more deeply buried rocks underwent metamorphism. Magma rose towards the surface and either erupted as lavas or cooled and crystallized as plutons below the surface. The land that is presently central Labrador experienced two such orogenies. The Labradorian Orogeny, about 1650 millioin years ago, produced he rocks that make up the Mealy Mountains.

The Grenville Orogeny about 1000 million years ago was a major cataclysmic event that produced mountains in southern Labrador that were once as high as the Himalayas. It added the last bit of crust to a landmass called Laurentia, which included much of what is now Greenland and North America. This ancient continent began to break apart again during Late Proterozoic times 600 million years ago. The Churchill River Valley and Lake Melville are situated within the wide rift which developed.

Glaciation

The most recent assault on the land was by glaciation which sculpted the landscape seen today. There were several "Ice Ages" during the last 2.5 million years and the last one ended about 10,000 years ago. Ice up to three kilometers thick covered the northern half of North America. Ice covering Labrador spread eastward from northen Quebec, pushing along the debris and gouging the land with embedded rock particles dragging along in the moving ice. Before the glaciation the region was a low plateau but the pre-glacial landscape was effectively destroyed.

The easily eroded sandstones infilling the Lake Melville and Churchill River rifts were scraped away and glaciers carved the U-shaped valleys. The rocks of the Mealies were too tough for the glaciers, hence remain as mountains. When glaciesr melted about 8000 years ago, meltwater laden with sand filled the Churchill River and a massive delta formed at the mouth. Sea levels rose and filled Lake Melville. Following removal of the great weight of ice, the land rebounded. Present wetlands along the shore were once submerged coastline. Happy Valley - Goose Bay is built on the amalgamated sandy deltas of the Goose and Churchill rivers. Gravel and sand deposits are examples of glacial till. The boulders strewn about are erratics, rocks broken off from much larger masses and carried along by the moving ice. Commonly one may find a boulder uncharacteristic of others in the area which was carried many kilometers from the west.

Today glaciers have retreated to the Arctic, but other forces of erosion (especially rivers) continue to change the landscape.

Geology of Melville Lookout

Geology of Birch Brook Melville Lookout, like most exposed rock in this area, is an outcrop of anorthosite, an igneous rock that crystallized from magma many kilometers below the surface of the Earth about 1640 million years ago and intruded into existing layers of rock which were later eroded. The main mineral in the rock is gray plagioclase, including labradorite, which is best seen when the rock face is freshly broken. Large dark crystals of igneous pyroxene can also be found but most of that mineral was metamorphosed to amphibole during the Grenville Orogeny 1000 million years ago.

More on the geology of Newfoundland and Labrador

References:

Colman-Sadd, Stephen and Scott, Susan A. Newfoundland and Labrador: Traveller's Guide to the Geology and Guideboot to stops of interest. Newfoundland Dept. of Mines and Energy, 1994.

Wicander, Reed and Monroe, James S. Historical Geology 2nd Ed. New York: West Publishing Co., 1993.

Thank you to Mr. Charles F. Gower of the Geological Survey, Department of Mines and Energy for reviewing geology notes and suggesting valuable changes.

Thank you to Mr. Bruce Ryan of the Geological Survey, Department of Mines and Energy for comments about anorthosite.