Malaspina Galleries
by Inge Riis McDonald
Title
Malaspina Galleries
Artist
Inge Riis McDonald
Medium
Photograph - Photography
Description
The Malaspina Galleries are formed from late Cretaceous rocks, about 70-65 million years old, and consist mainly of massive (un-bedded) sandstone, but with some thin layers of mudrock (lithified silt and clay).
After deposition of sediment ceased, but more than 40 million years ago, the rocks were folded and fractured, as were all of the rocks that make up the east coast of Vancouver Island.
Sometime, most likely in the last million years, a glacier removed a large �sliver� of this fractured sandstone. This created the bay exposing the ancient rocks.
After the glaciers retreated, the Malaspina Gallery was formed through differential weathering in the sandstone. Unlike sea caves, these galleries do not appear to be formed primarily by crashing waves. There are no barnacles on the back wall and the tide rarely (if at all) floods high enough the submerge the walkable ledge. The clay in the sandstone that cements the particles together is vulnerable to salt water attacking them. The amount and size of voids determine the strength of the sandstone. The "visor" component of the geological feature contains fewer voids and as a result the cement in stronger than the lower portion. As salt water seeps into the sandstone, either from the top or from the crashing waves, the rock behaves much like a sponge, and regular weathering is accelerated because of the weakness in the rock. This salt water attack is believed to be caused by the expansion of the salt after the water has evaporated, which then chips flakes of sandstone off. The seas can get quite stomy of Gabriola Island and the power of crashing waves is immense.various types of differential weathering caused by both fresh and salt water, exposing the old folds.
Eventually the roof of the Galleries will collapse and new erosional patterns will be created.
Uploaded
June 18th, 2013
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