Please refer to display rock 2 & display rock 3 for information on gneiss, metamorphism, and the Canadian Shield.

4Photo by Brent Eades.

Display rock 4 is Precambrian age gneiss with folded foliation that was produced at great depths by tremendous pressures from different directions.

Did mountains like the Himalayas really soar above Lanark County?

Yes! From about 1.7 to 1.0 billion years ago landmasses to the east collided with ancestral North America, called Nena, to form a larger continent called Rodinia.  These tectonic collisions created the greatest mountain chain the world has ever seen.


Public domain image by G. Mills via Wikimedia Commons.

The ancient roots of the Grenville Mountains extend across North America from Labrador to Mexico.


Public domain image by John Goodge via Wikimedia Commons.

 This map is a reconstruction of the supercontinent Rodinia 750 million years ago.  Highlighted in green are the mountain building belts of 1.1 billion years ago.  The creation of the Grenville Mountins added a 2,000 km long and 500 km wide belt to the eastern margin of what is now North America. 

Public domain photo of the United States Geological Service via Wikimedia Commons.

The tremendous forces of mountain building can deform the banding of metamorphic gneiss into complex fold patterns.


Photo by Julie Lantos.

The folded foliation of display sample 4 is highlighted with pink lines in this photo.  Felsic minerals started to recrystallize in the area outlined with blue lines. 

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