The Boundary Line EarthCache
Hidden : 7/11/2014
Difficulty:
2 out of 5
Terrain:
1 out of 5

Size: Size: other (other)

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Geocache Description:


Departure Bay marks the location of a very important piece of Nanaimo's geological puzzle. It marks the location of a boundary between two of the most influencial rock types of the area, and it demonstrates how glaciers affected the landscape many thousands of years ago.




What's the difference?
From where you are standing right now, you can easily see two very different types of rocks. Karmutsen formation basalt is to your North, while to your south are sedimentary rocks of a locally named "group".


Basalt is a type of volcanic rock formed when certain types of lava are cooled rapidly at or near the surface of the earth. The crystals inside are all tightly held together making it a very solid rock without empty spaces that air could get trapped in. This means it is also very hard to erode.

Sedimentary rock, on the other hand, is made up of many fragments of rocks cemented together. It has what is called a "clastic" structure. In this type of rock, lots of pore spaces exist meaning that this rock is more easily eroded.

So, what did the glaciers do?
Glaciation played a very large role in how Nanaimo's landscape came to be. The last glaciation to hit Vancouver Island was from around 100,000 thousand years ago up until around 14,000 years ago. At it's peak, almost 2km of ice covered much of the area, apart from some of Vancouver Island's highest mountains. As the glaciers slowly moved across the landscape, their great weight slowly wore away at the rock underneath. The sedimentary rock eroded faster than the basalt resulting in the landscape we see today: rocky basalt bluffs and mountains (such as Sugarloaf Mountain) seen to the North, lower lying sedimentary rock areas to the south. This area of Departure Bay was the borderline between the two types of rocks, and from this location you should be able to spot noticeable differences in the landscapes.






In order to log this Earthcache as found, please email me (through my profile page) the answers to the following questions:

1. Describe the visible difference(s) between the shoreline on the North side of Departure Bay and the South side? You should be able to tell by standing near the sign.

2. What popular hiking destination and landmark of Nanaimo is "entirely made up of basalt".

3. What is the name of the of the sedimentary rock group you are standing on right now?


Optional:

4. Post a photo of yourself/group/gps at Departure Bay.



Sources:
Geoscape Nanaimo - www.nrcan.gc.ca
Basalt, Departure Bay- en.wikipedia.org


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