Laurentia

Laurentia, also known as the North American craton, is a large and ancient piece of Earth's crust that 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 existed as a separate landmass, similar to how North America looks now. At other times, it was joined with other lands to form much larger continents and supercontinents.

Throughout its long history, many smaller land pieces called terranes, along with tiny continents and islands, moved toward Laurentia and joined with it. These collisions helped create the stable and strong land we see today.

Etymology

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

Interior platform

In eastern and central Canada, much of the stable landmass is visible as 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, this old rock is hidden under layers of younger rocks in the Midwest and Great Plains regions. It only shows up in a few places like northern Minnesota, Wisconsin, the New York Adirondacks, and the Upper Peninsula of Michigan. These layers of rock are made mostly of limestones, sandstones, and shales.

Greenland is also part of this landmass. Even though it is separated from North America by a strait, it shares the same ancient rocks.

Tectonic history

Laurentia started as small pieces of very old rock about 2 billion to 1.8 billion years ago. These pieces crashed into each other, forming a bigger landmass. Big mountains rose up, similar to the Himalayas today. Over time, more pieces joined Laurentia, making it grow.

Laurentia was once part of a huge ancient land called Rodinia. Later, Rodinia broke apart, and Laurentia became a continent on its own. It joined with other lands to form new big continents like Pangaea, but then 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 experienced many climate changes. In the late Cambrian and Ordovician periods, sea levels went up and down because ice melted. These changes caused layers of mud to form, which tell us about what happened long ago. Later, in the late Ordovician, the climate got cooler, though scientists are still learning exactly how much. Even later, in the Permian period, the world got warmer overall. Evidence from fossils shows that the western part of Laurentia stayed cooler than areas like Texas, even while the rest of the world was warming up.

Geological history

Laurentia is the ancient core of what we now call North America. Around 4.03 to 3.58 billion years ago, the oldest known intact rocks formed in what is now the Northwest Territories. Over time, Laurentia has been part of many different landmasses and supercontinents.

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