Chapter 11, Problem 1RQ

To determine

The term ‘Precambrian shield’ and the place where it is present in North America.

Answer to Problem 1RQ

The Precambrian shield is a large Precambrian portion of craton that is exposed to the surface of Earth. In North America, a Precambrian shield is present in Canada.

Explanation of Solution

The Precambrian shield is the nuclear area (that is exposed at Earth’s surface) of Precambrian rocks. The Precambrian includes 90% of the geologic time ranging from 4.54 billion years ago (when Earth formed) to 4 billion years later (start of the Cambrian period). Most of the geologic information about the Precambrian comes from cratons. Cratons are the large portion of the continents that are stable (have not undergone substantial tectonic deformation) since early Paleozoic time.

In Canada, the Precambrian shield is the largest. The Canadian Shield is one of the world’s largest geologic continental shields. This shield is primarily composed of igneous and metamorphic rocks but, also contain few sedimentary rocks.