Logging Requirements:
Earthcaches are designed to be educational. Like most Earthcaches, there is no log book or box to find with this cache. The reward is visiting the site and understanding your earth better.
Pretend you are a quantity surveyor for the quarry (and you happen to have a GPS - which is going to make this job much easier than the old school ways)
To claim a find you need to physically visit and DO TWO THINGS:
1. Email the cache owner (link off profile page) with your estimate of:
a) How DEEP and how WIDE the main quarry is (measure).
b) How much rock came out of the main quarry (calculate)
2. Post in Your Found Log something you learned about the geology of this site from visiting it (discover)
A couple hints:
Most GPS’s can tell you what elevation you are at when you mark a spot. Of course distance can be calculated with your GPS as well. It is unlikely that the rock excavated was shaped like a box, so you better adjust for that fact.
Why an Earthcache?
While today this part of Queen Elizabeth Park is a spectacular show garden in the second most visited park in Vancouver (after Stanley Park), you are here to learn more about the geological significance of this site. When you get to the coordinates, you will be standing on the rim of a former basalt quarry. This basalt quarry was developed as a source for relatively cheap, angular rock in the late 19th Century and early 20th century by the Canadian Pacific Railway (CPR).
What is Basalt?
Basalt is a common gray to black extrusive volcanic rock. It is usually fine-grained due to rapid cooling of lava on the Earth's surface. It may be porphyritic (means crystal containing) containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Basalt magmas form by decompression melting of the Earth's mantle.
Extrusive refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. This is opposed to intrusive rock formation, in which magma does not reach the surface.
The main effect of extrusion is that the magma can cool much more quickly in the open air (ie at QE Park) or under seawater, and there is little time for the growth of crystals. Often, a residual portion of the matrix fails to crystallize at all, instead becoming an interstitial natural glass or obsidian.
If the magma contains abundant volatile components which are released as free gas, then it may cool with large or small vesicles (bubble-shaped cavities) such as in pumice, scoria, or vesicular basalt.
How does the basalt here fit the description of extrusive rocks? What kind of extrusive rock does this look like? (good questions to consider when you log)
So what is Basalt good for?
The railway’s interest in the site was likely as a source of ballast (note this is a different word from basalt) which are the rocks you see under railway tracks. A good railway track ballast is strong, hard-wearing, stable, drainable, easy to clean, workable, resistant to deformation, easily available, and reasonably cheap to purchase or quarry. Crushed natural rock with particles between 28mm and 50mm in diameter makes good ballast. A high proportion of particles finer than this will reduce its drainage properties, and a high proportion of larger particles result in the load on the ties being distributed improperly.
Angular stones are preferable to naturally rounded ones, because angular stones interlock with each other, preventing track movement. Soft materials such as limestone are not as suitable because they tend to degrade under load when wet and this causes problems with the track. Granite, although expensive, is one of the best materials. Basalt and granite share many qualities and are closely related stone types.
Take a look at the basalt rocks here. Would they make good ballast?
So what has this quarry done for me?
The CPR sold a lot of rock from here for use under the Vancouver streets you drove on to get here. So thank the quarry there are nice solid streets to use in Vancouver.
Where else can we find basalt?
The dark areas visible on Earth's moon, the lunar maria, are plains of flood basaltic lava flows. We know this because of samples taken by manned American Apollo and the robotic Russian Luna missions, as well as from lunar meteorites.
Lunar basalts differ from their Earth counterparts principally in their high iron contents, which typically range from about 17 to 22 % FeO by weight.
Lunar basalts show exotic textures and mineralogy, particularly shock metamorphism, lack of the oxidation typical of terrestrial basalts, and a complete lack of hydration (no contact with water).
From Mars missions we know that Basalt is also a common rock on the surface of Mars.
Why does it look like this now?
William Livingstone, a deputy parks superintendant, designed the new park landscape without drawings, but from a clear vision in his mind. This excerpt is from an article written by Livingstone. Full article is accessible on the Vancouver Parks Board website linked a "User's Web Site" at the top of this page.
"The main quarry covers an area of approximately two acres and its horseshoe shaped cliffsides vary in depth from ___ feet to ___ feet to enclose the garden. The open end of the horseshoe provides an exciting vista of downtown Vancouver and across the waters of the harbour and Burrard Inlet to what are familiarly called the North Shore Mountains . Queen Elizabeth Park ranges from 300 to 500 feet above sea level. Preliminary surveys determined the elevation of the quarry floor and surrounding area in order to establish a pattern for installation of drainage, walks and access roads.
Weathered rock surfaces with unusual characteristics were marked and protected while cliff-side pockets for a waterfall and for collections of plants were blasted from the stone walls.
Pools were dynamited to a depth of 29 inches in the floor of the quarry and a constant water supply was tapped off a line serving the city's main supply reservoir which rests as a huge, fenced, rectangular lake atop the little mountain. (now covered)
Following grading for floor drains, a gravel base was placed over the entire area except the pools, to prevent water accumulation in lower spots. Soil was spread to depths varying from 12 inches to several feet to create a gently undulating garden with ample soil for lawns, flowers, shrubs and dwarf trees.
Surplus rock blasted from the quarry walls was source material for protective rockeries and for dry walls around the perimeter. “
Other uses – and why the Quarry closed:
Being this is the highest point in the City, the Civic Water Committee was pretty interested in the site. So early on the CPR sold off a small part for a water reservoir. The need for the reservoir may have helped stop the quarry use from continuing to remove Little Mountain bit by bit.
By 1911 the quarry was closed permanently. The Vancouver Parks Board website states that “the dreadful scar of its works (was) left like a raw wound on the landscape.” Of course to those that love rock quarries that statement might be a bit bias, but to each his/her own.
Failure to follow the logging requirements may result in log deletion. As the Earthcache founder, we are required to maintain the integrity of logged visits. Thank-you for visiting the Queen Elizabeth Park Earthcache. We hope you enjoy learning more about the earth and history of Queen Elizabeth Park.
Information gathered from:
Various Wikipedia Articles for the technical explanations of rocks, railway ballast uses, and Moon/Mars examples of basalt. Vancouver Parks Board Site for the main quoted material and additional background. http://www.city.vancouver.bc.ca/parks/parks/queenelizabeth/h,pistory.htm
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