The Skystone Erratic and Archaeological Site--Bonney Lake, Washington

This is the Skystone (also known as Sky Stone). It is a glacial erratic located in Bonney Lake (which is east of Tacoma, Washington). The Skystone is a somewhat rectangular-shaped rock with a flat top. It is located in Skystone Park--which is in the greater Sky Island residential area (it is located a short distance from the playground area). The Skystone boulder is surrounded by a chain-link fence with an unlocked gate that allows access (at least during my visit). There is a small interpretive sign within the enclosure--although much of the enclosure area is overgrown with vegetation (making photography difficult). Please be respectful to preserve this historic and culturally important rock for future generations (it appears that someone has carved some letters into a locality on the rock).
The Skystone is significant in multiple ways. Regarding the geological significance of the Skystone, it is a granitic erratic. It traveled to this locality within glacial ice, and only was exposed upon the glacial ice melting event. As an erratic, it originated from a distant area. It does not match nearby bedrock types. It may have originated as far away as Washington’s North Cascades, or southwestern British Columbia. A boulder of this large size, attests to the immense power of the glacier that once filled the Puget Sound Lowland. The Puget Lobe ice sheet filled the area between the Cascade Range and the Olympic Mountains. At Bonney Lake, the glacier was perhaps two thousand feet thick (or about 600 meters).
The boulder sits on a very rocky area, locally called Sky Island. The area is an old Ice Age delta, associated with a glacial river that once drained into Glacial Lake Puyallup (but now is the Puyallup River Valley). Note that a small part of this Ice Age delta has been used as a local gravel pit (nearby--at the base of the valley slope). [ en.wikipedia.org/wiki/File:01... ].
The Skystone has cultural and archeological significance to the Puyallup Tribe too. Tribal songs mention the Skystone site. A study by archaeologist Gerald Hedlund in 2000, noted a number of "pits" on the stone surface that may be man made. There are steps and perhaps 20 drilled holes in the rock [Reference: products.kitsapsun.com/archiv...]. Although the purpose for these "pits" are not certain, sticks may have been placed in the "pits" to potentially create site lines for purposes of a calendar or observatory. The "pits" may appear to align to one or more of the following: 1) Cascade Range mountains-such as Mount Rainier, and 2) align to the seasonal position of the Sun, and some major stars (such as the North Star).
For these reasons, the Skystone has been deemed an archaeological site by the Washington State Office of Archaeology and Historic Preservation. An article relating the positions of these "pits"-with potential distal targets-has been published. [Reference: books.google.com/books?id=-S3...].
Note that there are also some andesite boulders in this area. An andesite is a gray-color lava rock. Most of the andesitic rocks and boulders in this area originate from Mount Rainier (within the Osceola mudflow--about 5,600 years ago). Less common, but nearby, are older andesite rock mudflow deposits--also from Mt. Rainier. [These are older than the Ice Age deposits that are at the top of the Puyallup River Valley. The older mudflows have been glacially compacted-unlike the post-glacial Osceola mudflow deposit.]
The Skystone is weathered and covered with moss. It appears to be granitic (but I did not want to damage it to confirm its composition). This granitic composition implies that the Skystone originated with glacially transported sediments from the Puget Lobe glacier. This makes sense, since the dominant rocks in the Sky Island residential development area, is dominated by glacial sediments (erratics). There are a number of nearby andesitic rocks nearby too, but there seems to be few in the Skystone area.
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