Northern Cape Breton Island is dominated by a highland block of ancient metamorphic and granitic rocks. Deep valleys, which dissect all sides of the block, are habitat for damp, cool deciduous forests (District 220). On the southward-sloping plateau surface, generally above 300 m, the short growing season and severe climate
allow only a Balsam Fir forest to grow (District 210).
The rocks of the Highlands reflect a long and complicated geological history. The oldest rocks, located north of Pleasant
Bay and the Cabot Trail, are similar to strongly metamorphosed rocks of the Canadian Shield and are about as old (about 1.2 billion years old). The central part of the Highlands contains younger Precambrian
and Middle Paleozoic volcanic and sedimentary rocks. Deformation (folding) and metamorphism vary in intensity. The Precambrian rocks include marbles and quartzites, as well as volcanic rocks that were mapped as the George River Group. Late Devonian and Carboniferous rocks rest unconformably on the older rocks.
|Valley & Highland Plateau
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1. Oldest Rocks in Cape Breton
The Precambrian geological history of the Highlands is complex and represents many periods of deformation and metamorphism. Precambrian rocks were deformed and metamorphosed approximately one billion years ago, and again about 600 to 570 million years ago. Many geologists believe the very high temperature-and-pressure metamorphic rocks of the northwest Highlands, the Blair River Complex, belongs to ancestral "North America." Precambrian metamorphic rocks of the central Highlands were deposited prior to the Late Precambrian deformation and metamorphism of about 600 to 570 million years ago. Late Precambrian to early Cambrian diorites and granites were intruded into the older rocks.
2. Pre-Middle Devonian
The Early and Middle Paleozoic history of the Highlands is somewhat clouded by variable amounts of deformation and metamorphism. Where rocks are somewhat undeformed, the original textures of volcanic and clastic sedimentary rocks are visible. Radiometric dating of the volcanic units show their ages to range from
Middle Ordovician and Late Silurian. Granites were intruded in the Ordovician and Late Silurian. Middle Devonian and younger periods of erosion have stripped away some of the older rocks.
3. Middle to Late Devonian
The lack of a strong indication for the Middle to Late Devonian Acadian Orogeny is unique to the Cape Breton Highlands. Elsewhere in Nova Scotia, the Acadian Orogeny was a major folding event created as continental plates collided in the formation of the supercontinent Pangaea. Study of the Highlands indicates that its rocks were deformed and metamorphosed in the Late Silurian, which is not the "usual" Acadian time.
4. Carboniferous Sea
During the long period that Nova Scotia was part of Pangaea, sediments deposited in the Carboniferous Sea eventually covered most or all of the Highlands Region and the adjoining Plateau-Taiga Region. Only occasional remnants of these strata are now found on the highland plateau, such as the late Carboniferous block of
Canso sandstone that can be seen near the western entrance to Cape Breton Highlands National Park. During the late Carboniferous, the highland block appears to have moved vertically upwards and deformed the Carboniferous strata. In places, these Carboniferous rocks are domed upward at the margins of the Highlands.
5. Mesozoic Erosion
DuringthetimebetweenthePermianandCretaceous periods, the Highlands underwent another period of erosion. The Carboniferous strata were stripped from the older rocks and the area now occupied by Region 100 and 200 was part of a planation surface that extended across the Maritimes.
6. Tertiary Uplift and Erosion
During the Tertiary, the planation surface was uplifted and tilted. After that, another period of erosion once more exploited variations in rock resistance across the flat eroded surface. The Cape Breton Highlands are situated on the highest part of the tilted plain and have thus been subjected to the greatest degree of erosive attack.
Landscape Development (Faulting)
Another important element of the morphological character of the Highlands block is the combination of faults found around its margin and crosscutting its interior. The boundaries of the Highlands are in places depositional (where softer Carboniferous strata have been deposited directly onto older metamorphosed rocks) and
in places faulted. In either case, erosion has preferentially exploited the softer material and exposed a steep scarp slope at its margins. Faulting has defined the straight sides of the Highlands on the east and west, influencing the angular drainage patterns of many rivers and streams. The two main fault directions are north-northeast and
west-northwest, with the former predominating.
The principal fault in the Highlands is the Aspy Fault, which runs southwards from Cape North (see Figure 5). For 40 km its position is shown by a straight escarpment that continues across the Highlands as a straight line of river valleys and reappears on the south side of the Margaree River Valley. The ancient Aspy Fault shows
evidence of movements dating back to the Ordovician period. Other faults have also been exploited by rivers which rise well towards the interior of the Highlands and form long, steep-sided and V-shaped valleys at the margins, e.g., Grand Anse River, Ingonish River.
Some upland masses are isolated by faults, for example, Sugar Loaf Mountain in the interior, and Gairloch Mountain on the southerly margin of the Highlands.
The climate of the Boreal Forest Region in the Cape Breton Highlands is influenced by elevation and by winds blowing off adjacent ocean waters. Its main features are cold long winters, short cool summers, and high precipitation. It differs from the climate of the Plateau-Taiga Region mostly as a result of the lesser impact of the
wind (see Region 100).
Because there are no weather stations in the Region, detailed climatic information is not available. Although the mean annual temperature of less than 5°C is not markedly colder, the daily temperature range is considerably greater than in other areas in the Maritimes. The beginning of winter, as marked by a continuous layer of
snow 2.5 cm deep, usually occurs in the Highlands in early or mid-November. Snowfall is heavy, but accumulations are limited by frequent episodes of rain and thawing. Records for weather stations in an adjacent Region at Chéticamp and Ingonish Beach show that mean daily temperatures in January, February, and March are consistently
lower at Chéticamp, reflecting the influence of winds that blow mainly from the north and northwest over the frigid, ice-covered waters of the Gulf of St. Lawrence. This east-west difference is also noticeable in parts of the Highlands.
Summer temperatures start to rise sharply in May and fall abruptly in September. Mean daily temperatures in July are somewhat cooler in the Highlands than in most other interior areas of the province.
More than 1600 mm of precipitation falls each year in the highest areas of the Region. Elsewhere, amounts range between 1400 and 1600 mm. The higher precipitation recorded on the eastern side of the Region is evidence of the effects of an Atlantic rain shadow. More than 400 cm of snow falls on most of the area, with lesser
amounts being recorded on the Atlantic side because of the slightly warmer winter temperatures. The snow cover melts in late April or May.
This Region is shrouded in fog or low-level clouds many days of the year, and relative humidities are high. Interesting microclimatic features include cold-air drainage and fog in the canyons, and high relative humidity and low sunlight exposure for north-facing cliffs in steep-walled canyons.
The growing season is short, but tree growth is rapid, except where strong winds stunt growth on exposed ridges.
The main drainage pattern is radial, and rivers follow the fault lines in the bedrock. The steep-sided river valleys do not develop floodplains or wide intervales until they leave the Highlands; however, an exception to this general rule is the Margaree River, which has a broad intervale extending well into the Highlands.
The few small glacial lakes and wetlands are dystrophic and have low conductivity levels. Biological diversity is also low.
This area was not mapped in the soil survey of Cape Breton Island because of its inaccessibility. However, it is now known that the soils are considerably better than the blanket designation "Rough mountain land" would suggest. The soils are mostly heavily podzolized sandy loams, which are surprisingly deep considering that
the underlying rocks are highly resistant. The depth of the soils suggests that the Highlands were protected by a static ice cover during the last glaciation. One interesting feature is the steep slope of the sides of the Highlands plateau surface.
The Cape Breton Highlands Region falls within Loucks' Gaspé-Cape Breton Ecoregion. Balsam Fir, White Birch, and White Spruce are the main species, forming what is essentially the true Boreal Forest Region in Nova Scotia. The main influences on the regional vegetation are cool temperatures, high precipitation, and the effects
of wind and insect damage. Because of inaccessibility, cutting was not a major disturbance factor until the 1970s. Since the Spruce Budworm salvage project, large areas of dead Balsam Fir have been removed. Replanting with Black Spruce is taking place in some areas. Stands of fire origin are present but uncommon.
On the slopes fringing the plateau the true boreal forest is replaced by the Acadian Forest association - shade-tolerant hardwoods along the steep-walled canyons on the eastern and western coasts, and predominantly softwoods on the Atlantic slope in the northeast corner of the Region. The shade-tolerant hardwoods - Yellow
Birch, White Birch, and Sugar Maple - are mainly found between 200 m and 300 m above sea level. On the plateau, barrens and bogs are common.
This Region is interesting because of the diversity of floral elements represented. The northernmost limit for Alleghanian tree species (for example, Sugar Maple) in the Atlantic Provinces is found here. Also represented are the arctic-alpine and the Cordilleran elements. The Cordilleran flora in Cape Breton is usually restricted to wooded ravines, or damp, cool deciduous and mixed woods; it is more commonly found in similar cool, moist habitats on the pacific coast or along the Rocky Mountains.
The fauna of the Highlands reflects this Region's boreal character and its status as one of the few large areas in Nova Scotia which remain relatively inaccessible. Boreal species such as the moose, Snowshoe Hare, and lynx are found here. Larger carnivores such as bear and perhaps cougar have a large range of undisturbed habitat. Deer are present during summer and fall but are restricted in distribution by the deep snow in winter and spring. Also present here are disjunct species with a generally northern or mountain distribution elsewhere, for example, the Rock Vole and the Gaspé Shrew. Region 200 offers a wide range of habitats, which include more areas of mature woodland, both hardwoods and softwoods, than are found in the other Regions. Other habitats include bogs, barrens, cliffs, and talus slopes.
The Highlands form a distinct landscape component of Cape Breton, and its many communities are largely of Scottish descent. Where soil was good, farming was undertaken in the early 1800s; however, by 1820 only marginal farmlands were available. Many Scottish migrants later abandoned these less-productive soils,
permitting successional forest regeneration. Today, only the best land in this area is farmed, and many communities depend on the sea for a living. Balsam Fir forests on the plateau have been impacted by fires, Spruce Budworm, and, more recently, clearcutting to salvage timber ravaged by budworm infestations. Seasonal hunting continues in
this area; however, tourism and recreational activities predominate because of the impressive scenery and wildlife attractions of the Cabot Trail and Cape Breton Highlands National Park. Highlands watersheds were harnessed to create a major hydroelectric power plant in Wreck Cove in the early 1970s.
Introduction to the Geological History of Nova Scotia
Granite in Nova Scotia
Development of the Ancient Landscape
Nova Scotia's Climate
Plant Communities in Nova Scotia
Cliff and Bank
Hardwood Forest (Sugar Maple, Yellow Birch, Beech Association)
Mixedwood Forest (Spruce, Fir-Maple, Birch Association)