Ellison Ridge is the approved name (North Okanagan Commonage, lakecountrymuseum.com, retrieved 24/10/2015) for the highland between Okanagan Lake and Kalamalka and Wood Lakes. This highland displays both volcanic and glacial activities. The tower formation itself is made of dacite columns, and the chemical composition of these columns is evidence that the volcanic action which formed this feature also formed Mt. Boucherie, Knox Mountain, Munson Mountain, Layer Cake Hill, Black Knight Mountain, and Giant’s Head Mountain. This group is named the “Marama Formation” (Okanagan Geology, 2014, Murray A. Roed and John D. Greenough editors). The dacite columns formed when the magma oozing from underground rose upwards through weak spots in the surface rocks, and then cooled quickly forming the columns.
Glacial action in the Okanagan Valley also shaped this ridge. Specifically, the ridges are steeper on the northern sides and gentler on the southern (down-steam) sides. This shaping is more obvious on the hills to the east and west and much less obvious on Spion Kop itself. The lakes visible from The Grand Lookout – Kalamalka, Wood, and Ellison are all modified kettle lakes, as are parts of Okanagan Lake which is visible from the summit itself (Okanagan Geology, 2014, Murray A. Roed and John D. Greenough editors).
To log this earthcache please send a message to the cache owner with the answers to the following questions:
- Estimate the height of the tower from GZ to the top
- Estimate the size of the large dacite block close to GZ.
- What is the average thickness (width) of the small individual dacite columns found within the big rock?
- Do you see more 4-sided, 5-sided, or 6-sided columns within the big rock?
- Is the surface texture of the dacite rough or smooth?
An online copy of the trail guide can be found here: http://sweetlife.com/wordpress/wp-content/uploads/2012/07/walkingtrails.pdf