Tuesday, September 6, 2016

Vedder Wall

For a time Vedder Mountain acted as a divide between continental glacial ice on the northwest of the ridge and an ice free valley on the southeast side of the ridge. The ridge line raises over 1,500 feet above the Sumas Valley floor. The elevation from the picture below is only about 30 feet and the ridge line is 1,500. The trees growing out of the cliff face obscure the dramatic scale of the valley wall. The valley was formerly a lake bed and the Nooksack flowed into from the south before the Nooksack avulsion at Everson. The area still would be a swamp to lake if not for pumps operated in Canada that maintain the drainage of the valley. The Sumas valley in Canada is considered one of the richest tract of farmland in Canada.

There was very little flow at this waterfall given the dry weather.
I estimate that the falls is approximately 300 feet to 350 feet
Most of Vedder Mountain consists of Chilliwack Group metamorphic rocks. The formation is a former island arc perhaps as old as Devonian. The Chilliwack has been correlated with the East Sound Group. It is one of several accreted terranes in the Northwest Cascades/San Juans.  
The top part of the ridge on the southwest end is underlain by much younger and non metamorphic Huntingdon Formation. The Huntingdon was deposited on the Chilliwack roughly 50 million years ago. A deep weathered zone of ancient soil has been observed in some of the areas below the Huntingdon. This weathered zone of thick clay was mined for brick material in the early 1900s. 
DEM of Vedder Mountain area.
Sumas Valley is the dark green area in center
The valley southeast of Vedder Mountain has an elevation of 520 feet

The valley to the southeast was for a short time occupied by a very large river. The continental glacial ice flowing down the Fraser valley to the northeast flowed along the base of the mountains during the late stages of the last glacial period. The ice blocked the Chilliwack River which then flowed southwest to the Noooksack valley.4
Conceptual DEM of Fraser ice block Chilliwack  

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