"Unique, and so distinct from its surroundings as to suggest rather the handicraft of man than a whim of Nature, it looms up at the entrance to the Narrows, a symmetrical column of solid grey stone. There are no similar formations within the range of vision, or indeed within many a day's paddle up and down the coast. Amongst all the wonders, the natural beauties that encircle Vancouver, the marvels of mountains, shaped into crouching lions and brooding beavers, the yawning canyons, the stupendous forest firs and cedars, Siwash Rock stands as distinct, as individual, as if dropped from another sphere." Pauline Johnson
Geology of Stanley Park:
The beauty of Stanley Park is generally observed in the majesty of a great forest, surrounded by water and urban living. It's an island of wilderness, rugged coastline and beaches visited daily by both the residents of Vancouver and visitors from across the globe. The soil and rock underneath the impressive forest cover is not readily visible to the naked eye except where the coastline rises up in cliffs around the north and west sections of the Park. This is the focus of this EarthCache.
Most of Stanley Park is composed of sedimentary rock that dates back approximately 50 to 70 million years ago. The sedimentary rock of Stanley Park consists of sandstone and mudstone, and is found relatively close to the surface we see today. Other areas of the Lower Mainland have more glacial till covering the sedimentary rock, rendering it invisible to the eye. The sedimentary rocks near Second Beach date back 50 million years, while the sedimentary rock at Prospect Point dates back 70 million years. So as you walk northward along the seawall from Second Beach to Prospect Point, you actually walk back in time.
Both Prospect Point and Siwash Rock are examples of volcanic basalt dykes: molten basalt that rose like a sheet through existing sedimentary rock, and crystallized when it came to the surface about 32 million years ago. When it reached the earth's surface, the magma cooled and hardened, creating a basalt stack, resistant to weather. Basalt is a common extrusive volcanic rock, usually gray to black and fine-grained due to rapid cooling of lava at the earth's surface.
Over the years (32 million of them), the sandstone rock surrounding the basalt stack of Siwash Rock eroded and a Sea Stack was formed. A Sea Stack is an isolated rock more resistant to erosion than sedimentary rock. Where Siwash Rock was once part of Stanley Park and surrounded by sandstone, time and erosion has created a solitary pillar separated from land. The Sea Stack, Siwash Rock.
A number of remarkable Sea Stacks have been found around the world. Another Sea Stack found along the West Coast is Haystack Rock, in Oregon State, USA. Haystack Rock is much younger than Siwash Rock, dating back approximately 10 - 17 million years.
Cultural History:
Along with it's geological significance, Siwash Rock also known for it's cultural significance: A West Coast legend speaks of a young man who was bathing in the waters off this coast, purifying himself in anticipation of the birth of his first child. As he swam, a canoe bearing agents of "The Great Tyee" came along and ordered him out of the way. He refused to stop swimming, as he was engaged in a rite of purification. They were angered at first, but once they understood the young man's dedication to his new son's future, they gave him freedom from death, by having him live for eternity as a monument. A plaque can be found at Siwash Rock, stating that the Rock stands as a symbol of "fatherly cleanliness".
Between the years 1914 - 1971, a stone seawall was constructed around the perimeter of Stanley Park, to protect the exposed coast from erosional forces, and provide access to the public. The federal government helped finance seawall construction until 1967, because it owned the park at the time, and it was argued that the waves created by passing ships were eroding the coastline. Much of the original wall was constructed under the direction of James "Jimmy" Cunningham, a master stonemason who spent 32 years on the project until his death in 1963. His ashes were scattered near Siwash Rock, and a plaque can be found on a nearby cliff wall, recognizing him for his commitment to the seawall construction.
Siwash Rock was also dubbed "Siwash Fort", during the first and second World Wars. Guns and naval volunteers were posted in the area to protect Burrard Inlet from any foreign intruders. Remnants of the Fort can still be found on top of the cliff nearest to Siwash Rock.
References used to research this cache:
Johnson, Pauline, E. (1911). Legends of Vancouver. Vancouver: Thomson Stationary Co.
Clague, John J.; Alison Parkinson, Vancouver Natural History Society (2006). Wilderness on the Doorstep: Discovering Nature in Stanley Park. Vancouver: Harbour Publishing, pp. 169 - 175.
Clague, John J. and Bob Turner (2003). Vancouver: City on the Edge. Living with a Dynamic geological landscape. Vancouver: Tricouni Press.
To Log this Cache:
- Take a look around and note the differences between the basalt rock of Siwash Rock and the sedimentary rock on the vertical cliffs along the seawall;
- Observe some of the forces at work along this coast that might accelerate erosion of the sedimentary rock around Siwash Rock and the remaining cliffs;
- Estimate the volume of sedimentary rock between Siwash Rock and the existing cliff that would have eroded over the past 32 million years (the calculation is not as important as imagining the incredible volume of material that must have eroded over the years);
- Post a photo of your caching group and your GPS either in front of Siwash Rock, or with some example of erosional forces in the vicinity, and;
- Document your observations above, and email them to the EarthCache owner. The EarthCache Guidelines insist on a learning component for this cache to be successful, and for the log to count as a find.
Please note, if complete responses are not sent to the cache owner before the GC is logged as found, the log will be deleted.