Send the link below via email or IMCopy
Present to your audienceStart remote presentation
- Invited audience members will follow you as you navigate and present
- People invited to a presentation do not need a Prezi account
- This link expires 10 minutes after you close the presentation
- A maximum of 30 users can follow your presentation
- Learn more about this feature in our knowledge base article
Is my area geologically ACTIVE or QUIET??
Transcript of Is my area geologically ACTIVE or QUIET??
Location - Where am I?
I live in the geologic area called the Great Lakes and
St. Lawrence Lowlands. It is located
in Southern Ontario and can be divided into
either the Great Lakes Lowlands or
the St Lawrence Lowlands.
I live in the Great Lakes Lowlands.
My area (as a combined unit) is coloured
on the map.
Geologic History - The Bedrock
The foundation of the St. Lawrence Lowlands is sedimentary rock, formed during the Devonian period of the Paleozoic era (advance the show here, don't worry, you will come back). The bedrock in my area is formed of progressively younger sedimentary rock, which originates on the south side of the Canadian Shield (The Paleontology Portal). This sediment was a direct result of the shallow seas which covered alternating parts of Southern Ontario throughout history (The Paleontology Portal). I have found lots of limestone around here with fossils of various sea creatures in them! When these ancient seas retreated from an area, erosion would occur, then the seas would return, producing disconformities in the sediment layering.
Tectonics In My Area
It has been suggested that Southern Ontario and its two neighboring basins were formed by Paleozoic tectonic activity, which also involved the neighboring Appalachian orognes (better known as Appalachian Mountains) and created the Algonquin Arch (AECOM Canada Ltd. and Itasca Consulting Canada, Inc., 2011). All of the above mentioned landforms can be seen in the image at right (will be enlarges when the shows advanced). The creation of these two basins is hugely important because, as you may note, the bottom of the Michigan basin (the westward one) would be a crucial draining point to Lake Michigan. Also, these tectonic movements continue today as post-glacial uplift occurs (land lifts back up after weight of ice) (AECOM Canada Ltd. and Itasca Consulting Canada, Inc., 2011). This figure also again shows London very well; you can see that my town (near London) sits on a base of limestone.
You are about to see a very large map of Ontario, the star in Southwestern Ontario is near London, my approximate location. You may have to finish the show then zoom in on the map, it's very interesting. The green patch in Southwestern Ontario represents the Devonian period (Paleozoic era) sedimentary bedrock. Also, the legend includes multiple symbols of various types of mining. It is easy to see how much variety the rest of Ontario has in comparison!
Wondrous Water - Glaciers and Lakes
Many landforms in my area have either been gouged out by ancient glaciers or formed by ancient water bodies as glaciers retreated, such as the Great Lakes (Great Lakes and St. Lawrence Lowlands). During the Pleistocene Epoch, a 4km - thick glacier called the Laurentide Ice Sheet covered the vast majority of Canada and the Northern US (Michigan Environmental Education Curriculum). The Laurentide Ice Sheet completely reformed much of Canada's surface geology, and in an equal feat, managed to popularize ice rinks in Canada before Toronto ever even lost a game! (Advance show to see image)
As this giant sheet of ice gouged its way across Canada, it caused a huge amount of erosion, carving valleys and mountains out of the landscape, such as this one (Great Lakes and St. Lawrence Lowlands). (Advance here)
About 14,000 years ago, this gigantic glacier began to retreat (Michigan Environmental Education Curriculum), and left behind a marred landscape. Also, as the glacier melted, it obviously produced liquid water, which had to go somewhere. That "somewhere" was the Great Lakes of today. (Advance here)
The effects of the glacier are still evident in other ways which are a little closer to home. The rolling landscape of Southwestern Ontario is attributed to this glacier, and our soil is a type of "till" left behind by the glacier (David J. B. Baldwin). This soil is some of the best in Canada and if one takes a walk in a field, one can easily see the broken up rocks scattered in the soil.
The Big Melt - Laurentide
Rivers and Local Erosion
While looking out my window, I can see the forested border between my town and a farmer's field; I know this forest harbors one of the most powerful forces of nature: a stream. In fact, this "forest" I have mentioned is in a remarkably large gulley, especially remarkable is that the stream responsible for reshaping the face of the Earth in this little patch of the world is only 2 meters wide, at the most. However, this stands a testament to the amount of water erosion that occurs in my area. I have before mentioned the steep bluff and deep hole my local river has carved out of the landscape. I even just recently went tobogganing at a very large, steep hill which had been crafted by a fast-flowing river (today, the river is far from its old size).
I attribute the amount of water erosion around here to two things. Firstly, each and every one of the rivers I have mentioned have gravel beds (I should know, I usually wind up in them unintentionally). This gravel is a great abrasive and works like sandpaper against the second part of the erosion double-whammy, our deep soil and sedimentary rock.
People - Aiding Erosion
Living near the centers of Ilderton, Lucan, and London, (the first two are popping up suburbs like crazy), I can see that it would be wrong to leave ourselves out of the erosion issue. Firstly, the streams and rivers I mentioned earlier? They are the number one output for farmer's field tiling (water run-off). This adds water to the rivers, which would have would up in the soil and groundwater otherwise. More water increases the flow rate and therefore, the erosion, too. Secondly, the amount of building around here aids erosion; as houses are built, the soil is loosened around them (or usually straight-up trucked in). While most subdivisions are built with drainage systems, I have seen the result of the working of the topsoil before a rain on a job site. Finally, on the note of working topsoil, farming can wreck havoc on the land as well. Farmers literally go out before they plant and intentionally loosen up the soil (tilling). If it rains shortly after this is done, valuable and fertile topsoil is washed away.
Well... ARE the Great Lakes Lowlands
Active or Quiet?
Coming into this project, I figured recent geologic activity in my area would be pretty much nil. However, as I have discovered through this project, my geologic area was quite active in the past and, much to my surprise, actually continually active! I only needed to open up my eyes and take a look around from a different perspective! I have also discovered The Laurentide Ice Sheet and just how powerful the forces of glaciation can be!
Pictured: Bedrock and ancient seas
Works Cited in Addition to Course Material:
AECOM Canada Ltd. and Itasca Consulting Canada, Inc. (2011, 03). OPG's Deep Geologic Repository for Low and Intermediate Level Waste. Retrieved 01 16, 2014, from Regional Geology -Southern Ontario: http://www.nwmo.ca/uploads/DGR%20PDF/Geo/Regional-Geology---Southern-Ontario.pdf
Brock University. (2005, 05 08). Geology of Ontario. Retrieved 01 15, 2014, from brockedu.ca: http://www.brocku.ca/earthsciences/people/gfinn/methods/Geology_of_Ontario.pdf
David J. B. Baldwin, J. R. (n.d.). Chapter 2. Retrieved 01 17, 2014, from Physical Geology of Ontario: http://www.ubcpress.ca/books/pdf/chapters/ecology/chapter2.pdf
Great Lakes and St. Lawrence Lowlands. (n.d.). How the Area Was Formed. Retrieved 01 17, 2014, from Great Lakes and St. Lawrence Lowlands: http://greatlakesstlawrencelowlands.weebly.com/how-the-area-was-formed.html
Michigan Environmental Education Curriculum. (n.d.). How Did the Great Lakes Form. Retrieved 01 17, 2014, from techalive.com: http://techalive.mtu.edu/meec/module08/GreatLakesPastandPresent.htm
The Palentology Portal. (n.d.). Ontario, Canada. Retrieved 01 17, 2014, from The Palentology Portal: http://www.paleoportal.org/index.php?globalnav=time_space§ionnav=state&state_id=70
By: Jake Gregory