To examine how J.W. Dawson thought about coastal erosion, I searched the OCR content of the first edition of Acadian Geology (1855) for relevant terms and concepts.
Dawson used the term ‘erosion’ only once, in relation to glacial action. However, in several examples he described examples of coastal erosion as shore “wasting” or cliff sections that had “fallen“.
The coal-formation rocks of Port Hood and Margarie are evidently only the margin of a coalfield extending under the sea, and perhaps as far as its appearance above the sea-level is concerned, in great part swept away by the waves. This coast is now rapidly wasting, in consequence of its exposure to the prevailing westerly winds blowing across the whole width of the Gulf of St Lawrence ; and its rivers and harbours are from this cause choked with shifting sands. Owing to this waste of the coast, a sand-beach which connected Port Hood Island with the mainland has been swept away, and a safe harbour has thus been converted into an open roadstead, exposed to the northerly winds and encumbered with shoals. This will prove a serious drawback to any attempt to work the coal-beds of this locality. (p. 293)
The description of changes at Port Hood was by far the clearest example of the process of coastal erosion that identified an impact on community resources and structures. But there were other observations that Dawson made after returning to the same location and noting significant changes had occurred.
[east of Swan Creek] “This section was examined in 1846. When I revisited the place in 1850, the front of this mass of trap conglomerate had fallen, and formed a large slope of fragments. (p. 87)
” Another testimony to the same fact is furnished by the rapidity with which huge piles of fallen rock are removed by the floating foe from the base of the trap cliffs of the Bay of Fundy” (p. 52)
Other statements describe how eroded material was rapidly transported or how the material features of rock (soft, friable, or resistant) affected its susceptibility to erosion.
” The amygdaloid beneath, being friable and much fissured, falls away in a slope from the base of this wall, and the sandstone in some places forms a continuation of this slope, or is altogether concealed by the fallen fragments of trap.” (p. 68)
“In this valley, the red sandstone, in consequence of its soft and friable nature, is rarely well exposed;” (p. 69)
“We need not be surprised that we do not now perceive any regular volcanic mountain or vent at Blomidon, for independently of the action the waters : may have exerted on it when being formed, we know that great denudation has taken place in the drift-period, and under the wasting action of the present frosts and tides.” (p. 71)
Cape Blomidon and the geology of the Bay of Fundy shoreline was commonly described in terms of the erosional processes he observed.
“The bay shore presents to the sea a range of cliffs and precipices often overhanging or vertical, or rolled down into shapeless heaps of rubbish by the frost and the undermining action of the waves. Huge landslips occur every spring from these causes, covering acres of the shore with their ruins, and affording a rich harvest to the mineralogist who may visit the shore after one of these falls. The amount of debris annually thrown clown and removed in this way is enormous. The cliffs are usually composed of alternate layers of soft and hard trap and tufa, they are traversed by innumerable fissures, and the general dip is seaward. In addition to these circumstances, the ice annually removes large quantities of fragments from the shore, so that a cliff does not long continue to be protected by the masses that have fallen from it. Hence the whole shore wastes rapidly, with the exception of those places where beds of hard basaltic trap run down to the sea level, and form inclined planes against which the sea rages in vain.” (p. 73)
“On the western coast of the county, the cliffs fronting Chignecto Bay and Cumberland Basin, and which have been cut and are kept clean and fresh by the same agencies which we have already noticed in treating of the trap and new red sandstone coasts, furnish the finest and most complete section of the carboniferous rocks in Nova Scotia, and one of the finest in the world” (p. 121)
“The deposition of marine mud in the Bay of Fundy has afforded many interesting illustrations of geological facts, and may afford more; and the agency of coast-ice in removing masses of rock, and otherwise acting on the shores and cliffs, is a subject at present of much interest,”(p. 367)
But other sites were also used to describe the processes we recognize today as coastal erosion, including Prince Edward Island.
[PEI] “In approaching this place the red sandstone forms long undulations sloping gently toward the shore, and the coast displays a series of low points, terminated by red sandstones, which, though not hard, have better resisted the wearing action of the waves than the softer strata which have occupied the intermediate creeks. (p. 105)
In other sections Dawson discusses the importance of exposure and richness of Nova Scotia’s fossil record, being exposed and washed away, and as context of discoveries included the famous discovery of vertebrate fossils inside the trees at Joggins.
“The fossil remains of this system still afford a large field for discovery. The great interest of the discoveries already made, shows that Nova Scotia is equal to any country in the world in the opportunities which it offers in this department ; and in a country where so many curious relics of the ancient world are constantly being exposed and washed away in the coast cliffs, even persons themselves unacquainted with geology may advance the interests of science by preserving such specimens, and making them known to those who can decide on their scientific value.” (p. 366)
“The reptiliferous tree of 1851 had fallen from the cliff before it was observed” (p. 33).
Dawson also points out about the relationships of the bedrock to features of the agricultural land (geodiversity) and suggests a connection with the nature of the people who live in the regions.
The agricultural capabilities of the trap are very different from those of the red sandstone. The soil, formed of decomposed trap, is very rich in the mineral ingredients most necessary to cultivated plants. It produces in its natural state a most luxuriant growth of timber, and yields excellent crops when recently reclaimed from the forest; but, perhaps from its porous and permeable texture, it is said not long to retain its fertility. I fear, however, that very bad methods of farming have generally been applied to it. The situation and exposure of the trap are singularly different from those of its contemporary the red sandstone. The latter usually appears in low and sheltered valleys. The trap, on the other hand, forms steep acclivities and high table-lands, exposed to the full force of the storms and changes of an extreme and variable climate; while its ranges of rugged cliffs, with their cascades, their terrible land-slips, and the wild beating of the winds and waves upon their bare fronts, present nature in an aspect altogether different from that which she wears in the quiet valleys of the red sandstone. These differences are, even in this new country, not without their influence on the mental and moral tone of the inhabitants of these dissimilar districts. (p. 99)
Although Acadian Geology contains abudnant illustrations, very few were used to display the processes of erosion. The cliff at Ogden’s Lake shows a recently fallen boulder and trees leaning over the actively eroding cliff. Because Dawson relied on drawing for detailed observation, before the advent of photography, Dawson was unable to observe the process of coastal erosion with any great detail over an extended period time.
The true impact of coastal erosion would have to wait for the increased use of photography to carefully document the erosion of geology sites.
References
Dawson, J. W. 1855. Acadian Geology : An Account of the Geological Structure and Mineral Resources of Nova Scotia, and Portions of the Neighbouring Provinces of British America. Edinburgh: Oliver and Boyd. http://hdl.handle.net/10222/76659.
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