Access to this earthcache location is via the Okanagan Rail Trail. The nearest entrance point is from Leathead Road but parking is limited and is across Highway 97. The McCurdy road or Dilworth road access points have more nearby available parking.
Dilworth Mountain, as well as nearby Mount Boucherie, Knox Mountain, Black Knight Mountain, and Layer Cake Mountain were formed by volcanic activity about 50MYA. These peaks were formed by lava which solidified at the Earth’s surface. The resulting rocks are basaltic which is very fine-grained. Basalt which cools on land often forms columns. Some examples of basalt columns can be seen at several nearby earthcaches including GC65T83 (Spion Kop Towers) and GCAF3QA (Basalt Columns Revisited). Long after the volcanic activity ended this part of North America was covered by glaciers. The Okanagan Lake area was covered to a depth of one to three kilometers by the Cordilleran ice sheet which flowed towards the south and southeast. This glaciation lasted until about 17,500YA, and as the ice melted about 13,000 years ago a large lake, Glacial Lake Penticton, was formed behind a large ice plug to the south. At its highest, the lake surface was at about 475m above sea level. The Okanagan Lake surface is about 340m above sea level. The benches of the glacial lake consist of deposits of mainly fine sand with smaller amounts of coarser sand and clay laid down by glacial streams carrying a heavy sediment load into the lake. Where the water was flowing rapidly there are pebbles and cobbles embedded in resulting sandstone but where the water was still the sand grains are quite small. An excellent example of clay deposited in Glacial Lake Penticton can be seen at a nearby earthcache - GC34J9W (Glacial Lake Penticton Varved Clay).
While standing at ground zero look up across the paved rail trail toward Dilworth Mountain. You should see a small cave eroded into the cliff face.
To log this earthcache please send your answers to the following questions:
- What is the elevation at GZ? Would this area have been underwater when Glacial Lake Penticton was at its highest?
- Is the rock surrounding the cave basaltic or sedimentary? What evidence do you see to support your answer?