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July/August 2006 issue	In this issue Table of Contents Feature: Moose mystery Feature: Century club Feature: Honey Ranchers The Inside Story Editor’s Notebook Reverberations Explorer À la carte Mosaic

Shape-shifting
Ocean became mountains became plains as the ancient Canadian Shield was stitched together in northern Manitoba and Saskatchewan
By Steven Fick

Canada’s largest earth science project, Lithoprobe, is now nearing completion and challenging some long-held thinking about the rock that lies deep beneath our feet. The 20-year $100 million project involved some 1,000 scientists who probed the geology under 10 study areas across the country.

In one such area in northern Manitoba and Saskatchewan, Lithoprobe discovered a turbulent history. “Geologists were absolutely astounded about how wrong their interpretations had been from previous studies based only on surface geology,” says project director Ron Clowes.

The area is underlain with Canadian Shield bedrock, one of the oldest and least active parts of the Earth’s crust. Yet at one time, the region looked more like today’s earthquake-prone Indonesia and, later, like the towering Himalayas.

“Mining companies are using the technology we demonstrated and the knowledge we acquired from Lithoprobe to tap new mineral deposits,” says Clowes. But for those who are simply fascinated by how alive and dynamic the Earth has always been, he says, it’s hard to find a better story than this.

The Earth’s continents have continued to shift their positions around the globe, but remnants of the early mountain chain (BELOW, middle) can still be traced from Colorado to Manitoba, Saskatchewan, Baffin Island, Greenland and Scandinavia.

1.9 billion years ago		1.81 billion years ago		Today
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Thought to be about the size of today’s Pacific, the Manikewan Ocean shrank to a small sea as ancient continents converged. Volcanic islands formed when fragments of ocean crust slid under one another at the edge of tectonic plates, similar to the current active geology around Indonesia.		Just as today’s Himalayas are being shaped by the collision of Asia and the Indian subcontinent, the continents bordering the Manikewan Ocean were crushed together, creating mighty mountain ranges.		After the forces that powered the continental collision subsided, water, ice, wind and gravity eventually levelled the chain of mountains, leaving a relatively smooth plain. Sedimentary rock (grey) later covered the older bedrock (brown).

Nelson House, Man., sits where one of the last portions of the Manikewan Ocean disappeared.

Cross Lake and Norway House, Man., are situated on what is known as the Superior craton, one of the ancient continents that was joined by the mountain chain.

La Ronge, Sask., Lynn Lake, Leaf Rapids and Flin Flon, Man., are located on mineral-rich bedrock that was formed in the volcanic islands of a shrinking Manikewan Ocean. Mines in these regions now tap ore deposits of gold, silver, copper, zinc, lead, nickel and platinum.

Sediments that originally collected underwater along the edge of the closing continents created the bedrock under Thompson, Man.

Saskatchewan’s Cree Lake lies in the Athabasca Basin, a layer of rocks made up of the sediments that were washed down from eroding mountains.

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