Vanier Park - Vancouver
Between Ganville St. and Kits Beach
Lake Superior AgateMoose Lake Agate and Geological Interpretive Center
Downtown Vancouver with Burrard St. bridgefrom the north end of Kits Beach
Minnesota State Fair fireworks from our back yard....with a 400mm lens
More than a billion years ago, the North American continent began to split apart along plate tectonics. Molten lava upwelled into iron-rich lava flows throughout the Midcontinent Rift System, including what is now the Minnesota Iron Range region. These flows are now exposed along the north and south shores of Lake Superior. The tectonic forces that attempted to pull the continent apart, and which left behind the lava flows, also created the Superior trough, a depressed region that became the basin of Lake Superior.
The commonly accepted theory of Agate formation:The Multiple Solution Deposition Theory
The formation of agates begins with an empty gas pocket or
vesicle that became trapped within cooling lava. At some point after the lava cooled and hardened cracks developed connecting the vesicles and produced a network through which ground-water flow. The timing of when the ground-water moved through the lava flows could have been shortly after they were deposited or millions of years later. As water moved through the lava pile silica was dissolved from the host rock and carried as a solution into the vesicles.
Once the silica-rich solution enters the vesicle, it fills the cavity which allows a thin layer of fibrous quartz called chalcedony to form on the inside surface of the cavity. This initial layer becomes the first band of agate in its formation. At some point, negative fluid pressure sucks out the solution leaving the cavity empty except for the thin layer of agate. Subsequent events of positive and negative pressure fill and empty the cavity. During each event a layer of chalcedony or agate is deposited that progressively fill the vesicle forming the agate.
webdom.org/pages/LakeSuperiorAgateActivity.pdf
(Page 14)
Looking towards Howe Sound and sunset from Kits
Downtown Vancouver with the north coast mountains
Looking west towards UBC and pastfrom Kits Beach
A nice shot of RaduCheck this poster from the Natural Resources Canada website:
(Map from previous post stolen from here)
http://geoscape.nrcan.gc.ca/vancouver/poster_e.php
