Brandywine Falls EarthCache

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Hidden : 5/10/2010
Difficulty:
2 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:

Brandywine Falls is a spectacular 70 meter waterfall located within Brandywine Falls provincial park, on Highway 99 about 47 kilometers north of Squamish.

The word “brandy” is actually the shortened word for brandywine. No one is completely sure about how the falls got their name, but one possible explanation is that two surveyors (Jack Nelson and Bob Mollison) for the Howe Sound and Northern Railway made a wager for a bottle of brandy about who could estimate more accurately the height of the falls. When the height was actually measured with a chain it was Mollison who won the bottle of brandy and Nelson then named the falls Brandywine.

Brandywine Falls Trail: Enjoy a 10-20 minute (one way) walk or snowshoe across the covered footbridge and through the forest to a new viewing platform overlooking Brandywine Falls. Continue along a new, short walking path to a second viewpoint of the falls and another of the surrounding area of Daisy Lake and the Black Tusk. Stay behind fences and away from the river’s edge. Use caution when crossing the Canadian National Rail line. Trails in the park are not maintained during the winter.

During times of high flow, the falls are spectacular. Brandywine Creek waters plunge 70m over the lip of a series of lava flows to the valley below. These lava flows are visible in relatively distinct horizontal layers. The igneous rock of the lava flow is more resistant to erosion than the rocks beneath them (much like Niagara Falls), thus the falls are maintained as they slowly retreat back upvalley.

Avalanches of incandescent ash, rock fragments, and gas can move down the flanks of a volcano during explosive eruptions or when the steep side of a growing lava dome collapses and breaks apart. These pyroclastic flows are as hot as 800°C, and move at speeds of 150-250 km per hour. These flows tend to follow valleys, knocking down and incinerating everything in their path. Low density pyroclastic flows, called pyroclastic surges, can overtop ridges more than 100m high.



Many basaltic lava flows, ranging in age from nearly 34,000 years old to the last glaciation, comprise the vertical walls surrounding Brandywine Falls. Fractures and stress joints were formed/exacerbated when lava came into contact with glacial ice in the valley below.


The Brandywine Falls geological formation are part of the Garibaldi Volcanic Belt, a northwest-southeast chain of volcanoes and related lava flows that form the northern end of the Cascade Volcanic Arc (includes volcanoes such as Mt. Meager, Mt. Baker, Mt. Rainier, Mt. St. Helens, Crater Lake, Mt. Shasta). The volcano that produced many of the lava flows comprising the edifice of the current falls is now extinct, with little if any remains.




Important Geological Terms


Columnar Basalt – A type of jointing in igneous rocks which results from internal contraction during cooling of lava, in this case basalt, which is a very common, fine-grained, usually dark colored basic igneous rock which is made of essentially plagioclase feldspar and pyroxene minerals, sometimes with or without olivine.

Fluvial Processes – terms pertaining to rivers and river action, respectively. They also refer to organisms which are found in rivers, and to anything produced by river action.

Gorge – A deep and narrow chasm with precipitous rocky walls, currently occupied or formerly occupied by a river. It is more steep-sided and enclosed than a ravine, but it is the same magnitude. Any river valley of broad floodplain and gentle bluffs may pass into a gorge as it traced up or downstream, possibly owing to the presence of a belt of hard rocks.

Igneous – Rocks that have formed from the crystallization and solidification of magma. They include Hypabyssal, Volcanic, Plutonic, and Pyroclastic rocks, and are classified according to their mineral characteristics, grain size, texture, and chemical composition (usually based on degree of silica saturation).

Lava Dome – A massive protuberance of lava forming a mountain with convex slopes, resulting from accumulation of numerous lava flows from a central vent in a volcano over a considerable period of time.

Lava Flow – A stream of lava issuing from a volcanic vent in the form of a narrow but lengthy emission. A basic lava flow is extremely mobile and may extend considerable distances, while a viscous lava flow will congeal more rapidly and will travel only a short distance from the vent.

Plunge Pool – A hollow at the base of a waterfall, thought to have been formed largely by cavitation.

Plunge Waterfall – A type of waterfall where water descends vertically, losing contact with the bedrock surface from the lip to the pool below.

Pyroclastic Flow – Fast-moving currents of hot gas and rock, collectively known as tephra, which travel away from the volcano at great speeds. The flows normally hug the ground and travel downhill, or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope. The word pyroclast is derived from Greek, pyro = fire, and clast = broken.

Pyroclastic Surge – A fluidized mass of turbulent gas and rock fragments which is ejected during some volcanic eruptions. It is similar to a pyroclastic flow but contains a much higher proportion of gas to rock, which makes it more turbulent and allows it to rise over ridges and hills rather than always travel downhill as pyroclastic flows do. Pyroclastic surges are much faster moving than pyroclastic flows, and can reach speeds of 1050 km/h.

Talus – An accumulation of fragmented rock waste below a cliff or rock face, formed as a result of disintegration, largely by mechanical weathering of rock exposure. It is usually of coarse particle size, has varying degrees of soil and vegetation cover and exhibits a concave slope profile.

Valley glacier – A glacier which occupies a pre-glacial valley, either as a result of the coalescence of several cirque glaciers, in which case it is an Alpine type of valley glacier, or one formed at the edge of an icecap or icesheet, in which case it is an Outlet glacier.

Volcanic Arc – A chain of volcanic islands or mountains formed as an oceanic tectonic plate subducts under another tectonic plate and produces magma at depth under the over-riding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone.

Logging the Earthcache:

In order to claim this earth-cache, please email Vadrosaul (via the profile link at the top of the page) with answers to the following questions. Although it is optional, pictures of you, your group at the earthcache site, and the falls would be greatly appreciated:

1. How many layers of lava flows do you see along the sides of the falls?

2. Describe where some geological formations, listed under Important Geological Terms, are in relation to the falls. Take pictures of them if you can and submit them (optional).

3. Take a walk to the waypoint Outlook #2, where the creek meets the Cheakamus river valley. If you look at the sides of the east & west ridges, you can make out the lava flows. How far do you believe the falls have retreated from the furthest advance of the lava flows?


References

BC Parks - Brandywine Falls Provincial Park
GSA - Floods, Faults, and Fire: geological field trips in Washington State and Southwest British Columbia
John Clague & Bob Turner - Vancouver, City on the Edge
John B. Whittow - Dictionary of Physical Geography
Alwin Scarth - Vulcan's Fury: Man Against the Volcano

Additional Hints (No hints available.)



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