25 FACTS ABOUT THE CANADIAN SHIELD MOST CANADIANS NEVER HEAR

Stand on the shore of Hudson Bay and you weigh a little less than you should. Satellites have measured it from orbit, and the old explanation, a vanished ice sheet, covers less than half of it. This is a countdown of 25 facts about the Canadian Shield, the ancient slab of rock under about half of Canada, from the lakes it holds to the one puzzle scientists still haven't fully solved. It starts with the basics most of us drive past without a thought. The Shield covers close to 5 million square kilometres and wraps around Hudson Bay like a horseshoe. Canada holds roughly 62% of the world's lakes bigger than 10 hectares, most of them on the Shield. The flat granite of cottage country was once the roots of mountains, and the ice of the last ice age stood kilometres thick over almost the entire country. Then come the records. The Acasta Gneiss, found by geologist Janet King in 1983 about 300 km north of Yellowknife, is just over 4 billion years old. Near Sudbury, an object 10 to 15 km across struck about 1.85 billion years ago, and the shatter cones in the bedrock still point back to where it hit. The crater became one of the richest mining districts on Earth, and it drew Apollo astronauts in 1971. Two kilometres underground near Sudbury, a tank of heavy water solved the mystery of the missing neutrinos and helped Art McDonald share the 2015 Nobel Prize in Physics. Farther north are the richest uranium mines on the planet in the Athabasca Basin, and the diamonds Chuck Fipke and Stewart Blusson found in 1991, at the end of a road made of ice. Finally, the ground itself. The land around Hudson Bay is still rising about 1 cm a year, old beaches sit stranded far from the water, water near Timmins has been sealed in the rock for about 2 billion years, and two satellites nicknamed Tom and Jerry mapped gravity over the bay. Why the scale on that shore will never read right is the very last fact. 00:00 Why you weigh less on Hudson Bay 02:04 Half a country made of stone 05:19 The oldest rock ever found 07:41 The crater under Sudbury 13:23 A physics lab 2 km underground 15:15 Uranium, diamonds and the ice road 17:00 The land that's still rising 19:00 Water 2 billion years old 20:19 Tom and Jerry weigh a ghost 21:34 The part nobody has solved #CanadianShield #HudsonBay #Geology