North American Craton (est. 3.8 billion years ago): North Eastern and Midwest Regions - Oldest Land Formation In America

A land formation refers to any natural feature of the Earth's surface or crust that has been shaped by geological processes over time. These processes include tectonic activity, erosion, weathering, deposition, and volcanic activity. A land formation has a distinct shape and structure and can vary greatly in size and type.

The North American Craton, also known as Laurentia, is considered an ancient geological core. It is the oldest land formation in North America at an estimated 3.8 billion years old. The United States Geological Survey (USGS) recognizes it as the oldest and most stable part of this continent. Live Science defines it as the oldest, thickest part of the continent.

The craton bedrock is exposed in northern Minnesota, Wisconsin, the Upper Peninsula of Michigan and the New York Adirondacks. The Adirondacks are a dome-shaped mountain range which is also considered the oldest vacation spot in America.

The Adirondacks is one part of NY state (northern part) that lies on the edge of the North American Craton and is considered the younger sibling in the Laurentia family. This region is geologically part of the Grenville Province. New York towns within or near the Adirondacks include Lake Placid, Saranac Lake, Tupper Lake, Keene and Elizabethtown. 

These billion-year-old rocks are not only visible on the surface in some areas of the Adirondacks, but also the Thousand Islands and regions of New York City such as Central Park. Although the NYC Manhattan Prong, while part of the craton, includes younger Proterozoic rocks, but it is situated within the broader context of the much older cratonic structure.

The craton is primarily composed of Precambrian rock, specifically Archean and Proterozoic igneous and metamorphic rocks. These rocks are some of the oldest on Earth, with the Canadian Shield exposing some of the earliest crustal materials, including rocks over 4 billion years old.

The craton consists of the basement rock, which is often covered by a relatively thin veneer of younger sedimentary rock. This stable core has been largely unchanged for over 600 million years, known as a craton due to its stability over geologic time scales.

Geographically, the North American Craton extends across much of North America, with the Canadian Shield in Canada and extending into parts of the United States where it's mostly covered by sedimentary rocks. Notable areas include the Archean provinces like the Superior Province.

The craton's evolution involves the accretion of numerous smaller tectonic plates or terranes over billions of years. It has been part of larger supercontinents like Rodinia and Pangaea. Throughout its history, Laurentia has experienced cycles of rifting, continental collision, and the creation of mountain belts through orogenic events like the Grenville orogeny.

It is layered like a cake, with older, thicker lithosphere beneath and younger, thinner lithosphere added around the margins. Seismic studies indicate a lithospheric root that is about 250 km thick under the oldest parts, suggesting a complex history of crustal growth by both subduction and accretion. The total size of the craton plate is 75,900,000 km2 making it the second largest of the 7 major tectonic boundaries on Earth.

The North American Craton hosts significant mineral resources, including nickel, copper, and gold, due to its ancient and stable nature, which has preserved these deposits over geological timescales.

Despite being stable, recent research has shown that even cratons can undergo deformation. For instance, studies suggest the root of the North American Craton may have shifted due to mantle flow beneath the continent.

Continuous geological, geophysical, and seismic research is conducted on the craton to better understand Earth's deep history, the processes of continental formation, and to explore for resources. Seismic tomography, receiver function studies, and analysis of xenoliths have significantly contributed to our understanding of the craton's deep structure.

The North American Craton is not only a subject of academic interest but also critical for understanding the continent's geological past, potential resource locations, and the dynamics of Earth's lithosphere.