[edit]
Map of select municipalities on Cape Breton Island
Travel map of Cape Breton Island, with major highways and freeways marked
The irregularly-shaped rectangular island is about 100km wide and 150 long, for a total of 10,311 square kilometres (3,981 sq mi) in area.
It lies in the southeastern extremity of the Gulf of St. Lawrence. Cape Breton is separated from the Nova Scotia peninsula by the very deep Strait of Canso. The island is joined to the mainland by the Canso Causeway.
Cape Breton Island is composed of rocky shores, rolling farmland, glacial valleys, barren headlands, highlands, woods and plateaus.
Geology[edit]
The island is characterized by a number of elevations of ancient crystalline and metamorphic rock rising up from the south to the north, and contrasted with eroded lowlands. The bedrock of blocks that developed in different places around the globe, at different times, and then were fused together via tectonics.
Cape Breton is formed from three terranes. These are fragments of the Earth's crust formed on a tectonic plate and attached by accretion or suture to crust lying on another plate. Each of these has its own distinctive geologic history, which is different from that of the surrounding areas. The southern half of the island formed from the Avalon terrane, which was once a microcontinent in the Paleozoic era. It is made up of volcanic rock that formed near what is now called Africa. Most of the northern half of the island is on the Bras d'Or terrane (part of the Ganderia terrane). It contains volcanic and sedimentary rock formed off the coast of what is now South America. The third terrane is the relatively small Blair River inlier on the far northwestern tip. It contains the oldest rock in the Maritimes, formed up to 1.6 billion years ago. These rocks, which can be seen in the Polletts Cove-Aspy Fault Wilderness Area north of Pleasant Bay, are likely part of the Canadian Shield, a large area of Precambrian igneous and metamorphic rock that forms the core of the North American continent.
The Avalon and Bras d'Or terranes were pushed together about 500 million years ago when the supercontinent Gondwana was formed. The Blair River inlier was sandwiched in between the two when Laurussia was formed 450-360 million years ago, at which time the land was found in the tropics. This collision also formed the Appalachian Mountains. Associated rifting and faulting is now visible as the canyons of the Cape Breton Highlands. Then, during the Carboniferous period, the area was flooded, which created sedimentary rock layers such as sandstone, shale, gypsum, and conglomerate. Later, most of the island was tropical forest which later formed coal deposits.
Much later, the land was shaped by repeated ice ages which left striations, till, U-shaped valleys, and carved the Bras d'Or Lake from the bedrock. Examples of U-shaped valleys are those of the Chéticamp, Grande Anse, and Clyburn River valleys. Other valleys have been eroded by water, forming V-shaped valleys and canyons. Cape Breton has many fault lines but few earthquakes. Since the North American continent is moving westward, earthquakes tend to occur on the western edge of the continent.
Climate[edit]
Sydney
Climate chart (explanation)
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F
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█ Average max. and min. temperatures in °C
█ Precipitation totals in mmSource: Environment Canada
Imperial conversion
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█ Average max. and min. temperatures in °F
█ Precipitation totals in inches
The warm summer humid continental climate is moderated by the proximity of the cold, oftentimes polar Labrador Current and its warmer counterpart the Gulf Stream, both being dominant currents in the North Atlantic Ocean.
Ecology[edit]
Lowlands[edit]
There are lowland areas in along the western shore, around Lake Ainslie, the Bras d'Or watershed, Boularderie Island, and the Sydney coalfield. They include salt marshes, coastal beaches, and freshwater wetlands.
Starting in the 1800s, many areas were cleared for farming or timber. Many farms were abandoned from the 1920s to the 1950s with fields being reclaimed by white spruce, red maple, white birch, and balsam fir. Higher slopes are dominated by yellow birch and sugar maple. In sheltered areas with sun and drainage, Acadian forest is found. Wetter areas have tamarack, and black spruce. The weather station at Ingonish records more rain than anywhere else in Nova Scotia.
Behind barrier beaches and dunes at Aspy Bay are salt marshes. The Aspy, Clyburn, and Ingonish rivers have all created floodplains which support populations of black ash, fiddle head fern, swamp loosestrife, swamp milkweed, southern twayblade, and bloodroot.
Red sandstone and white gypsum cliffs can be observed throughout this area. Bedrock is Carboniferous sedimentary with limestone, shale, and sandstone. Many fluvial remains from are glaciation found here. Mining has been ongoing for centuries, and more than 500 mine openings can be found, mainly in the east.
Karst topography is found in Dingwall, South Harbour, Plaster Provincial Park, along the Margaree and Middle Rivers, and along the north shore of Lake Ainslie. The presence of gypsum and limestone increases soil pH and produces some rich wetlands which support giant spear, tufted fen, and other mosses, as well as vascular plants like sedges.
Cape Breton Hills[edit]
This ecosystem is spread throughout Cape Breton and is defined as hills and slopes 150-300m above sea level, typically covered with Acadian forest.
It includes North Mountain, Kellys Mountain, and East Bay Hills.
Forests in this area were cleared for timber and agriculture and are now a mosaic of habitats depending on the local terrain, soils and microclimate. Typical species include ironwood, white ash, beech, sugar maple, red maple, and yellow birch. The understory can include striped maple, beaked hazelnut, fly honeysuckle, club mosses and ferns. Ephemerals are visible in the spring, such as Dutchman's breeches and spring beauty.
In ravines, shade tolerant trees like hemlock, white pine, red spruce are found. Less well-drained areas are forested with balsam fir and black spruce.
Highlands and the Northern Plateau[edit]
The Highlands comprise a tableland in the northern portions of Inverness and Victoria counties.
An extension of the Appalachian mountain chain, elevations average 350 metres at the edges of the plateau and rise to more than 500 metres at the centre. The area has broad, gently rolling hills bisected with deep valleys and steep-walled canyons. A majority of the land is a taiga of balsam fir, with some white birch, white spruce, mountain ash, and heart-leaf birch.
The northern and western edges of the plateau, particularly at high elevations, resemble arctic tundra. Trees 30–90m high, overgrown with reindeer lichens, can be 150 years old. At very high elevations some areas are exposed bedrock without any vegetation apart from Cladonia lichens. There are many barrens, or heaths, dominated by bushy species of the Ericaceae family.
Spruce, killed by spruce budworm in the late 1970s, has reestablished at lower elevations, but not at higher elevations due to moose browsing. Decomposition is slow, leaving thick layers of plant litter. Ground cover includes wood aster, twinflower, liverworts, wood sorrel, bluebead lily, goldthread, various ferns, and lily-of-the-valley, with bryophyte and large-leaved goldenrod at higher elevations. The understory can include striped maple, mountain ash, ferns, and mountain maple.
Near water, bog birch, alder, and mountain-ash are found. There are many open wetlands populated with stunted tamarack and black spruce. Poor drainage has led to the formation of peatlands which can support tufted clubrush, Bartram's serviceberry, coastal sedge, and bakeapple.
Cape Breton coastal[edit]
The eastern shore is unique in that while not at a high elevation, it has a cool climate with much rain and fog, strong winds, and low summer temperatures. It is dominated by a boreal forest of black spruce and balsam fir. Sheltered areas support tolerant hardwoods such as white birch and red maple. Many salt marshes, fens, and bogs are found there.
There are many beaches on the highly crenelated coastline. Unlike elsewhere on the island, these are rocky and support plants unlike those of sandy beaches. The coast provides habitat for common coast bird species like common eider, black legged kittiwake, black guillemot, whimbrel, and great cormorant.
Hydrology[edit]
Land is drained into the Gulf of Saint Lawrence via the rivers Aspy, Sydney, Mira, Framboise, Margaree, and Chéticamp. The largest freshwater lake is Lake Ainslie.
