Geology Photo of the Week # 21

The photo of the week today is of a Canadian National Heritage Site. It is located just outside of Dawson City, Yukon and is unassumingly called Dredge 4.  Those of you who read this blog regularly will know that I am a huge fan of the Yukon, which is the site of my field work, and love talking about the gold rush history of the region. Very few things embody this history better than Dredge 4…the Discovery Claim may be the only better spot. Dredge 4 really represents the industrialization of gold rush mining. Dredging took backbreaking labour once done by men with picks and shovels and turned it into a truly industrial operation. This method of mining very effectively purged what gold was left in the Klondike district. However, placer mining of this scale had a huge impact on the local environment as some of the other photos will show. However, despite the impact the dredge and its mark are still incredible relics of gold rush history.

A view of Dredge 4. (Photo: Matt Herod)

The next picture shows a schematic of how a dredge worked. The bare essentials are that the dredge would move along flooding the land beneath it so that it would float and all the while scooping up the gold bearing gravel below it. The gold was extracted inside and the cleaned gravels were “pooped” out the back of the dredge in large piles that litter the landscape today.

Schematic of a dredging operation. (Photo: Matt Herod)

The scoops that the dredge used to pick up the gravel. (Photo: Matt Herod)

Piles of gravel left behind by dredging operations. (Photo: Matt Herod)

An aerial view of Dawson from Google Maps. The lines snaking along the landscape are gravel piles from dredging.



Matt Herod is a Ph.D Candidate in the Department of Earth Sciences at the University of Ottawa in Ontario, Canada. His research focuses on the geochemistry of iodine and the radioactive isotope iodine-129. His work involves characterizing the cycle and sources of 129I in the Canadian Arctic and applying this to long term radioactive waste disposal and the effect of Fukushima fallout. His project includes field work and lab work at the André E. Lalonde 3MV AMS Laboratory. Matt blogs about any topic in geology that interests him, and attempts to make these topics understandable to everyone. Tweets as @GeoHerod.