Welcome To Wells-Gray Provincial Park, BC's 4th Largest Park!
At 5,250 km2 this park is a vast wilderness area only outdone by size by Tweedsmuir, Spatsizi, and Tatshenshini Provincial Parks. This park is visited by thousands of people every year, especially from Germany, due to its natural beauty and array of landscapes ranging from river valleys to alpine meadows. This park's boundaries are unique in that they follow the borders of the watershed and protect 60% of the Clearwater River's drainage basin, unlike most parks which are simply a square.
The arch from a safe viewpoint on the West Clearwater Road.
Geological History
The Murtle Plateau was created when a large wedge of land between two faults suddenly dropped hundreds of metres. This enormous "ditch" that was then created was gradually filled with lava layer by layer. These layers were rapidly cooled as they were deposited and created distinct layers of rock. Since these layers of rock were deposited at around approximately the same rate, they cooled around the same time between the lava cycles. As the layers cooled, the rock contracted and cracked leaving vertical rock columns (therefore known as columnar basalt). They are initially vertical but may be bent and twisted due to tectonic forces and folding. This is kind of like how mud dries and cracks on a dry lakebed. These cracks allow water to permeate inwards and freeze, which then expands, and break big chunks off at a time. This is why wearing a hard hat under Moul Falls isn't a bad idea!
Columnar basalt at Dawson Falls.
North America has undergone several ice ages, not just one as commonly believed. This valley has been filled with ice several times before, with the glacier up to a kilometer thick! As many know, water is extremely heavy and this massive, dense piece of ice exerted tremendous force as it moved its way down the valley. The lave beds were eroded heavily by this and the valley was scraped down tremendously, therefore leaving the cliffs you see today.
The valley and the ravines leading into it continue to be eroded by water and ice today.
What is a Natural Bridge?
A natural bridge is rare geological feature where erosion has created a hole in rock. Basically it is a really, really short cave. They can be created through a number of ways ranging from abrasion from wind in the desert, wave action on the ocean's coast, or rivers and ice such as in the Clearwater Valley. The columnar basalt makes this rock quite susceptible to ice wedging and the weathering has been accelerated. In a rock such as granite, this would take a much longer time.
To Log This Earthcache:
The answers must be sent to me through my geocaching.com profile. If the answers do not arrive with an accompanying log within a reasonable amount of time, I will have no choice but to delete your log.
1.) Tell me what colours you see in the rock face and bridge. Can you speculate what minerals cause these colours?
2.) What is the length of the bridge? Binoculars or high zoom camera lense would be helpful here.
3.) What is the wooden object located at the river's edge? What is it for? This will definitley prove you've been here :)
4.) Posting a picture would spoil question 1 for future visitors, so be creative with any pictures you take!
THANKS FOR VISITING!