Sentinels of Nature

Sentinels of Nature

Looking out over Placentia Bay, an expansive bank of grey-blue clouds looms close to the shore. In the distance, the clouds form a straight and distinct line just above the water, the clear white sky between the two.

It looks for all the world like someone has scrolled a perfectly defined white line to divide the sea and the sky. Nature has its moments. This sometimes imposing, always impressive body of water often feels like it has been there forever. While it may not be forever, the origin of the bay does indeed extend deep into the past. So, yes, maybe it is close enough to forever.

Rocks of Time

The bedrock below the sea bed of Placentia Bay owes its origins to the Precambrian to Devonian period. It would have been around 359.2 million years ago or earlier. It is sometimes difficult to even conceptualise such a span of time. The geological perturbations of the period yielded rocks that are generally sedimentary, metamorphic (rocks formed from existing rock that has been exposed to high temperature and pressure), volcanic, and granitic rocks. The latter are both of volcanic origins, with the only difference being that the former had solidified on or near the surface. So, Placentia Bay developed during turbulent times indeed.

Another type of bedrock observed on part of the sea bed consisted more of sandstone, siltstone, and limestone. These rocks formed somewhat later during the Carboniferous period, around 392.2 to 299.0 million years ago. At various places granitic plutons or intrusions had also penetrated these rocks. This included Red Island granite, so named because Red Island is comprised solely of granitic rock, hence, the definitive colour of this island.

The depth and underwater topography of Placentia Bay generally trends along a direction from the northeast to southwest. Much of the seabed of Placentia Bay developed during the Appalachian Orogeny, a mountain building episode that took place about 570 to 650 million years ago. This left an array of large structural domes and basins. Being around 350 m above sea level, the sub-peninsulas on the Avalon Peninsula form the domes. And it was the basins that, in time, became filled with water to yield the large bays that we now know as Placentia, Conception, St. Mary’s, and Trinity.

Flowing Ice and Snow

The underwater landscape developed as a direct response to the period of glaciation that swept over the continent, reaching its maximum extent about 21,000 years ago. If we could travel below the water surface, we would see myriad formations that are characteristic of a glacial terrain. Large oval shaped mounds known as drumlins, which average around 230 m wide, 10 m high and 795 m long, silently sit on the sea bed. Like the moraines, the sediment and immense boulders that had been carried by the ice, these formations remain as lasting reminders of the movement of the formidable glaciers as they advanced, receded, re-advanced, and then diminished. Placentia Bay stems from a well endowed geological heritage.

With an area of around 6,600 km2, Placentia Bay is the quite easily the largest bay in Newfoundland and Labrador. It stretches for around 146 kilometres along its mouth and boasts a coastline that raggedly extends for around 1,750 km. This ice-free bay is also dotted with over 300 islands of varying size, with Merasheen Island and Long Island being the largest and Red Island being the youngest and also one of the most recognisable, given its distinctive red hue.

This is a photograph of Red Island (source

As hinted by the water line along the coast in many places, the tidal range of Placentia Bay is over 2 metres with some confined areas experiencing ranges around 3 metres. The currents that flow throughout Placentia Bay are born in large part of the Labrador current that carries frigid waters from the north near Greenland. Following the coastline down through the Labrador Sea and along the eastern coast of the Avalon Peninsula, the Labrador current then swings up into Placentia Bay near Cape St. Mary’s. As it flows, the Labrador current encounters various other local processes such as the wind that help to stir things up. The result is usually some local up-welling of nutrients, the result being a high level of productivity in places like the Burin Peninsula and Cape St. Mary’s.

Dependent on the nature of the coastline, the Labrador Current will be more or less impeded in its flow along the coast of Placentia Bay. While some areas, such as in northwestern Placentia are more deeply embedded, other locales like around the Burin or Cape Shore, the coast is less curved creating less of an impediment for the current. Always hugging the coastline, the Labrador Current travels in an anti-clockwise fashion around the coast of the bay, until it flows out along its western part then on to the Gulf of St. Lawrence.

Beauty of the Boreal

Classified as being mid-boreal, the bay makes for a relatively placid environment. Summers are relatively short, cool, and wet while the winters have a generally mild temperature of around -4° Celsius. During the summer, the easterlies dominate while in the winter, thanks to the Gulf Stream, the balmy south-westerly wind is the prevailing wind direction that carries warm and moist air into the region. The temperatures range from -29° Celsius to + 29° Celsius with it usually being between -10 and +15. While there will be ice, it will rarely be particularly heavy ice.

In other respects, as many residents of the bay would attest, it tends to be foggy for much of the year.

With an average of 154 days of fog in a year, the region is regarded as being the foggiest place in Canada. Some people may question the merits of such a reputation, but the fog carries benefits for some flora, as it helps plants resist the stresses of becoming thoroughly dried out. Plus, when the sun does finally emerge, it is welcomed as it kisses the land and sea with its magical touch of life.

The myriad plants and animals who reside near or within the waters of Placentia Bay are reliant on one another, sometimes intimately, all in an effort to ensure their continued health and well-being—essentially their survival.

This is how it works, a medley of living and non-living elements joining together in a dance of life, their respective goals and needs periodically merging to work in common. Such are the intricate workings of the diversity of life. It is an element of the bay that we have come to value in numerous ways, thus lending spirit to Placentia Bay.

Comments are closed