Complex sentence: In the United States, the craton bedrock is covered with sedimentary rocks of the interior platform in the Midwest and Great Plains regions and only in northern Minnesota, Wisconsin, the Adirondacks of New York and the Upper Peninsula of Michigan is the craton bedrock exposed.
Split into simpler sentences: In the United States, the craton bedrock is covered with sedimentary rocks of the interior platform in the Midwest and Great Plains regions. Only in northern Minnesota, Wisconsin, the Adirondacks of New York and the Upper Peninsula of Michigan is the craton bedrock exposed.