Laurentia

Laurentia, also known as the North American craton, is a large and very old piece of Earth's crust. It forms the core of North America today. It is one of the oldest parts of the continent and has changed shape many times over millions of years.

Sometimes, Laurentia was a separate land, like North America today. At other times, it joined with other lands to form bigger continents and supercontinents.

Through its long history, many smaller land pieces called terranes, along with tiny continents and islands, moved toward Laurentia and joined it. These joining events helped make the strong land we see today.

Etymology

The large piece of Earth's crust called the craton is named after the Laurentian Shield. The shield got its name from the Laurentian Mountains. These mountains were named after the St. Lawrence River. The river was named to honor Saint Lawrence of Rome.

Interior platform

In eastern and central Canada, much of the land is part of the Canadian Shield. This area has very old rocks, some of the oldest on Earth. For example, the Acasta Gneiss is 4.04 billion years old, and the Istaq Gneiss Complex in Greenland is 3.8 billion years old.

In the United States, these old rocks are hidden under layers of younger rocks in the Midwest and Great Plains. They can only be seen in a few places like northern Minnesota, Wisconsin, the New York Adirondacks, and the Upper Peninsula of Michigan. These layers are made of limestones, sandstones, and shales.

Greenland is also part of this landmass. Even though it is far from North America, it has the same ancient rocks.

Tectonic history

Laurentia began as small pieces of very old rock about 2 billion to 1.8 billion years ago. These pieces crashed into each other and formed a bigger landmass. Big mountains rose up, like the Himalayas today. Over time, more pieces joined Laurentia, and it grew.

Laurentia was once part of a huge ancient land called Rodinia. Later, Rodinia broke apart, and Laurentia became its own continent. It joined with other lands to form big continents like Pangaea, but Pangaea also broke apart. Through all these changes, Laurentia stayed strong and is now the core of North America.

Paleoenvironmental change

During a long time called the Phanerozoic, Laurentia had many climate changes. In the late Cambrian and Ordovician periods, sea levels rose and fell because ice melted. These changes made layers of mud form, which help us learn about the past. Later, in the late Ordovician, the climate became cooler, though scientists are still learning how much. Even later, in the Permian period, the world became warmer. Fossils show that the western part of Laurentia stayed cooler than places like Texas, even when the rest of the world was warming up.

Geological history

Laurentia is the ancient core of North America. About 4 billion years ago, the oldest known rocks formed in what is now the Northwest Territories. Over time, Laurentia has been part of many different landmasses and supercontinents.

Laurentia was part of larger continents like Kenorland, Columbia, Protorodinia, Rodinia, Pannotia, and Pangaea. Sometimes, it was a continent all on its own. Finally, Laurentia became the core of North America and later joined with South America to form the landmass we now call America.