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4 Real Estate Show Place Sept 1978 A look at Geomorphological History HOW THE NIAGARA ESCARPMENT WAS FORMED The physical landscape of the Niagara Escarpment Planning Area exhibits a variety of The positions of these landforms rela tive to each other contain a record of much of the geologic and climatic history of Southern Ontario over an estimated time period of some million This area is a unique one it is a natural schoolroom in which the historical record of its own formation and volution is dis play lor all to sec While the most noticeable feature in most of the area is the scarp face itself many other features exist which arc the result of water ero sion the main process responsible for the formation of the escarpment and yet other landforms exist which arc attributable to other processes such as glacial on The chronology of events as shown on the exposed escarpment face shows beds or strata of rock these being initially deposited main ly as sediment falling to the bottom of prehistoric seas A succession of these seas covered parts of Southern Ontario from to 500 million years ago and each time the land was covered by sea a layer or layers of mud sand andor calcium mater ials was laid down on the sea floor These sediments have over the centuries undergone changes due to various physical and chemical in fluences Pressure due to movements within the earths crust and to the weight of the overlying materials has compacted the sedimentary lay ers squeezing the water out of them while at the same time a cementa tion process caused the deposition of mineral binding material between the grams of the sediments The end result of this process is the rock strata which make up much of the geologic structure of Southern Ont ario and which arc exposed in the Niagara Escarpment The layering is not uniform throughout the length of the ment There are regional variations which represent sediments of differ ent origins laid down at the same time but under different environ mental conditions For example sediments which have since devel oped into sandstone are the result of materials being transported by rivers from ancient mountains which bordered the prehistoric seas and deposited delta formations when those rivers entered the seas fur ther into the seas the materials laid down were of a more calcareous nature and developed into limestone or dolomite That is why we find that at near Niagara Falls the layer of the escarpment exposed at the bottom known as the shale is overlain with sandstone while at Owen Sound the shale is under rock known as Manitoulinc dolomite On top of the sedimentary rock strata sits material which is quite different in origin and nature from the sediments below This overbur den did not arrive until after the es carpment had been actually shaped This shaping was done mainly by water erosion and the resultant shape would not have evolved if the bedrock of the area had not been sedimentary in nature When the seas receded a rela tively flat limestone plain remained with the underlying rock strata slop ing gently to the southwest A drainage pattern of river and streams developed on this plain and its surface However some of the rock layers were more resis tant to erosion than others and where the most resistant layers out cropped at the plains surface an escarpment formed as the less resis tant rock material alongside was quickly eroded away As downward erosion continued below the thick ness of the hard cap rock lateral erosion also began to take place with the softer underlying shales and sandstones being removed first resulting in the unsupported over hanging dolomite cap rock then breaking off This process called sapping is ideally shown in Nia gara Falls itself See figure 2 In this way the Niagara Escarp ment was formed and its face re treated westwards The rale of re treat was not uniform throughout the length of the escarpment This is evidenced by the existence of outliers such as Rattlesnake Point near Milton and by deep valleys cut by rivers into the escarpment To day one can still see examples of Hits river erosion in the Beaver Val ley and Valley at Owen Sound the Dundas Valley near Hamilton and the Valley of the Twelve Mile Creek at St Cathar ines The same crosional process still seems to be working on the escarpment and its environs The next major event in the chronology of the area was the com ing of the ice sheets This was in fact a recent process relative to the time of deposition of the escarp ments basic rock materials Sec fig urc While the assoc iated with the work of water arc those as a result arc due to both erosion and deposition The glaciers in four ad vances over Southern Ontario while in their retreats they de posited materials Consequently over much of the escarpment area the surface are of glacial ori gin This is probably most apparent in the townships of Caledon Mono and Mulmur the Caledon to part of the escarpment area where the scarp itself has been iimiplelcly eovuuJ by gl ic- deposits Hit in the is typihul by rolling lulls and the local relief is more subdued than in other are is where the scarp face IS drainage pillcrns were greatly affected by glacial erosion jnd deposition The advances scoured out river valleys so that in stead of being V shaped they be come shaped Either advancing or retreating the ice deposited de bris and filled many of these ancient valleys In some cases the courses of streams were so altered by glac ial ion that the present day stream is not in its original valley the Niagara River being a notable ex ample See figure As the glaciers melted and re treated the water which resulted flowed as rivers into lakes which formed over much of Southern Ont ario These glacial nvcrs further modified the over or through which flowed by erod ing transporting and depositing such as sand and gravel These glacial river channels called spillways today hold vast quan tities of sand and gravel Evidence of such a spillway is seen at Mono The glacial lakes also played a part in shaping the landscape Wave action on the lakes modified parts of the escarpment area and indeed the scarp itself and left behind ele vated terraces or steps These were in fact the beaches of the glacial lakes Since the glaciers disappeared erosion of the land by wind and water has continued but not to the point of obliterating the historic re cord It can be seen in this general overview of its morphology that the Niagara Escarpment Area con tains an association of landforms which makes it unique Mi Erosion produced the Escarpment Gneisses or formed Erosion later reduced the I Rocks of Niagara Escarpment 1 AN Oldest Ontario flocks formed Northern IT Origin of the Earth west gsuwpioAg fJEsST Hi fiSRDvonian Silurian Pre Cambrian sou LAKE ERIE Niagara Escarpment The Niagara I part oj a gigantic geological Ontario Michigan and New York itali