My accidental discovery of this multi-use pathway along the newest section of North Vancouver’s Green Necklace Trail system came as a pleasant surprise not very long ago. As I walked the fresh pavement from its western trailhead I was enthralled by the playful images painted on the asphalt, the peek-a-boo views of the breathtaking scenery, and the fascinating array of boulders that had been trucked in to stabilize the hillside. It is one of these boulders that is the subject of this Earthcache.
Whether your trek brings you from the west or the east, you should easily be able to spot one particular eye-catching rock that is framed by seven smaller boulders. This distinctively-coloured boulder is an example of what is known as a medium-grade amphibole migmatite, and was likely brought here from the area around the Britannia Mine.
Migmatite is a type of metamorphic rock, which means it has undergone a change (or metamorphosis) due to exposure to sources like heat, pressure, or other geological processes. If you look closely at this boulder you will see bands of different colours visible on the surface, which is typical of metamorphic rock where many different types of rock can be brought together.
It is likely this sample was near to, but not engulfed by a magma chamber, possibly as a roof pendant, where the heat from the magma was enough to introduce the banding, but insufficient to transition the rock to an entirely igneous state.
Your task in logging this Earthcache is to answer the questions below. Please do not include your answers in your cache log, but rather email or message them to me via the links available on geocaching.com. Failure to submit your answers in a timely manner will result in your found log being deleted.
PLEASE DO NOT INCLUDE PHOTOS OF THE BOULDER IN YOUR LOGS!
(Huge shout out and much gratitude to geo-tek for his expertise and advice regarding this specimen.)
The questions:
- How would you describe the overall predominant colouring of the boulder?
- The boulder has some noticeable bands, or veins. What colour are these bands, and what type of rock are they most likely composed of?
- What other colours can you see on the boulder’s surface?
Thank you for visiting my Earthcache and I hope you enjoyed the time you spent here!