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• 1 media/IMG_8721b.jpg media/20210615_132624cr.jpg 2021-05-17T16:04:26+00:00 The Niagara Escarpment, 450 million years into the past 61 image_header 2023-11-14T19:35:47+00:00 The Niagara Escarpment provides a playground for residents of Niagara, a refuge for wildlife, a preserve of natural biodiversity, an invaluable area of groundwater recharge and emergence, and of course is a window into the geological past. Brock University is situated right at the top and the protected escarpment is literally right out the University's back door. We will explore the Niagara escarpment here in a geological context by examining its form, the materials of which it is made, and the processes that lead to its existence and morphology.
  
  The Escarpment (we drop Niagara locally) is a topographic feature called a cuesta commonly described as a scarp, a cliff, or a ridge, which is visible in Ontario from Niagara to Manitoulin Island. The Escarpment’s relief varies from tens to hundreds of feet and its form today is a product of erosion, much of which was the result of ice sheets which once covered southern Ontario. It is composed of several layers of shale, sandstone, and dolostone.
  The Escarpment actually extends further than Ontario (rocks don't care about our silly human boundaries) from east of Rochester, NY, across Manitoulin Island, and further through Lake Michigan’s western coast into Wisconsin. Because of the extent of the Escarpment, the rock units composing it change somewhat from one end to the other, largely a result of what was deposited in that place hundreds of millions of years ago and what was eroded before it could be covered with more sediment.
  To get a sense of the relief of the Niagara Escarpment around Brock, take a look at the pictures below that show the view to the east from about 180 meters elevation (above sea level, or asl) right above Grimsby at Beamer Memorial Conservation Area. Since we are looking eastward, we are looking along the Escarpment, the middle image outlines the visible Escarpment relief, the satellite image below illustrates the viewpoint from above and shows the topographic relief between the viewpoint and Brock. In the satellite image you can trace the outline of the Escarpment as the dark green lineation running roughly west-east. Way off in the distance from our viewpoint, Brock's prominent Schmon Tower can just barely be seen (the red line starts where the picture was taken in the west and ends at Brock's tower), with a face of the escarpment protruding between the vantage point and Brock's position (outlined in yellow). This can be seen on the elevation profile at the bottom, which follows the purple line on the satellite image of northern Niagara.
  The profile of the Escarpment is characteristically steep facing north (in Niagara) as you can see in the elevation profiles below, the first from the western end of the peninsula, and the second forming a northward line from Welland, through Brock's Campus, and on to Lake Ontario. (you can always view the full size image by clicking on it and selecting View Source File)
  
  Today most of the Niagara Region is covered in sediment from glacial lakes that preceded the Great Lakes as we know them today (see the map below). This is an amazing story in itself, but it all happened in the most recent geological past, in the Quaternary Period (and even then in just the last bit of the Quaternary) and right now we are interested in what is below the surface and as such what was on the surface in the past. The Escarpment lets us see the bedrock without even having to put a shovel in the ground. We will return to the recent geological history later to discuss the glaciation and erosion of the Escarpment.
  
  All of the rock units visible on the Escarpment's face continue underground to the south. These units have been eroded and largely removed to the north of the Escarpment. Under the Quaternary deposits of eroded rock, soil, glacial deposits, and lake deposits are bedrock units of great age. On a large scale, the bedrock geology of Niagara is very simple, about as structurally simple as geology can be. There are several layers originally laid down horizontally, stacked on top of each other and sitting at a slight angle (we call that dip) such that the layers angle down to the south. These layers reveal the history of the region hundreds of millions of years in the past.
  
  Below is a map with the rock units identified by their age. The Escarpment generally outcrops along the north side of the Silurian bedrock (where the tan colour meets blue) but the bottom-most layer of those Silurian rocks may extend north ahead of the Escarpment. This is all dependant on how the Escarpment rock was weathered in each locality. Remember that in Niagara the bedrock at the surface gets younger as you go southward.
  
  
  To compare, if you're interested, below is what the bedrock geology of Ontario looks like at a large (1:250k) scale (click on it to enlarge). You may notice that the "middle" of Ontario is quite complex but both the north and south have simpler arrangements of similar aged rock. That middle bit, at least north of Lake Huron, is some of the oldest rock on the planet, the Canadian Shield. It was there long before the sediments of Southern and Northern Ontario were deposited on its flanks. In the south, between the Shield and our much younger Paleozoic (541 to 252 Ma, meaning between 252 million years ago and 541 million years ago) sediment are the Central Metasedimentary Belt and the Central Gneiss Belt, but that's a different story... The take-away from the map below regarding the Escarpment is that the sediments were deposited on the flank of older rock. Niagara's bedrock has a story that largely occurs in the Ordovician, Silurian and Devonian Periods, which is what we will discuss in the next couple sections.
  
  The Ordovician, Silurian, and Devonian are Periods, as set out by the International Commission on Stratigraphy which is the authority on such matters. A Period is a subdivision of geologic time, with larger units being Eras and then Eons. Below is a portion of the chronostratigraphic chart relevant to Niagara's bedrock which includes the time in millions of years (Ma for mega annum). As you can see, the bedrock of Niagara including the Escarpment predates the dinosaurs (which lived in the Mesozoic, 252-66 Ma) but is much younger than most of Ontario which is Pre-Cambrian (>541 Ma). You can get the full chronostratigraphic chart here.
  
  To develop an understanding of the Escarpment without trying to become experts (for now) we will focus on the composition of the Escarpment in the neighbourhood of Brock University south of Lake Ontario. In particular we will follow the units as they have been revealed by erosion at Niagara Falls. The rock of the Escarpment largely falls into three categories: shale, sandstone, and limestone/dolostone. So the next section will explain what those are and in what types of environments they form. Feel free to skip around if you like by using the index at the bottom of this page.
  
  
  
  Interested in chemistry, biology, and physics, but looking for a way to combine them all?
  Through Earth Sciences you can become a Geologist or Environmental Geoscientist who applies those subjects to our natural world. One of the great things about the geological and environmental fields is that they allow you to combine your knowledge of seemingly disparate scientific disciplines to further our (humans that is) understanding of our own planet and our neighbouring planets. Some people in geology/environmental science work in labs, some in the field, and many in a combination of both.
  You can learn more about options to study here: Brock Department of Earth Sciences.