The Geography of the United States and Canada

The Geography of the United States and Canada — page 3
THINK LIKE GEOGRAPHER OLD ROCKS RICH RESOURCES North America is made up of some of the oldest rocks on Earth The continent was built up on a continental shield called the Canadian or Laurentian Shield which is huge about 3 million square miles 7 8 million sq km The shield is centered on Canada’s Hudson Bay It’s the biggest chunk of exposed Precambrian rock on Earth While much of the shield is exposed across Canada it’s mostly covered by sedimentary rock in the United States except for a few areas including the Adirondack Mountains The Appalachian Mountains stand to the southeast of the shield and the ranges that include the Rocky Mountains the Sierra Nevadas and others stand to the west The Great Plains and other lowlands lie between them A A CONTINENTAL SHIELD IS A HUGE STABLE LOW AREA IN EARTH’S CRUST SHIELDS ARE MADE OF PRECAMBRIAN ROCKS THAT CAN BE ANYWHERE FROM 540 MILLION TO 3 BILLION YEARS OLD 6