W2 - Geology of Ontario

Question 1

How old is the Canadian shield?

Answer 1

2 to 1.5 by

Question 2

What is the Great Unconformity?

Answer 2

Missing (due to erosion) 1 by between the lower Paleozoic and Precambrian layers

Question 3

What are the 4 geological layers of Ontario?

Answer 3

1) Precambrian plate collisions and mountains - Canadian shield
2) Lower Paleozoic tropical seas
3) Pleistocene glaciation
4) Present day built landscape

Question 4

When was the Paleozoic sedimentary rock layer deposited?

Answer 4

600-300 mya; covered Canadian shield

Question 5

How old are the Niagara escarpment rocks?

Answer 5

400-500 my; landform itself is relatively young

Question 6

How was the Niagara escarpment formed?

Answer 6

By glaciation and fluvial erosion

Question 7

How has Niagara Falls changed over the years?

Answer 7

Undergone ~10km of erosion backwards over 12 500 years to reveal Paleozoic rock beneath

Question 8

What is undercutting?

Answer 8

Erosion of rock layer below the resistant cap rock causing the retreat of the cliff

Question 9

Give an example of undercutting?

Answer 9

In the Niagara escarpment/falls, the Rochester Shale formation is undercut, causing the Lockport Dolostone formation to break off and cause its retreat; similar processes have produced waterfalls and valleys in Hamilton area (ex: Tiffany Falls)