Columbia, also known as Nuna or Hudsonland, was one of Earth's ancient supercontinents. It was first proposed by John J.W. Rogers and M. Santosh in 2002 and is thought to have existed approximately , in the Paleoproterozoic Era. The assembly of the supercontinent was likely completed during global-scale collisional events from 2100 to 1800 million years ago. Columbia consisted of proto-cratons that made up the cores of the continents of Laurentia, Baltica, Ukrainian Shield, Amazonian Shield, Australia, and possibly Siberia, North China, and Kalaharia as well. The evidence of Columbia's existence is provided by geological and paleomagnetic data. Size and location Columbia is estimated to have been approximately from north to south at its broadest part. The eastern coast of India was attached to western North America, with southern Australia against western Canada. In this era most of South America was rotated such that the western edge of modern-day Brazil lined up with eastern North America, forming a continental margin that extended into the southern edge of Scandinavia. Assembly Columbia was assembled along global-scale 2.1–1.8 Ga collisional orogens and contained almost all of Earth's continental blocks. Some of the events associated with the assembly of Columbia are: The cratonic blocks in South America and West Africa were welded by the 2.1–2.0 Ga Transamazonian and Eburnean Orogens; the Kaapvaal and Zimbabwe cratons in southern Africa were collided along the c. 2.0 Ga Limpopo Belt; the cratonic blocks of Laurentia were sutured along the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava, Torngat, and Nagssugtoqidain Orogens; the Kola, Karelia, Volgo–Uralia, and Sarmatia cratons in Baltica (Eastern Europe) were joined by the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volyn-Central Russian, and Pachelma Orogens; the Anabar and Aldan Cratons in Siberia were connected by the 1.9–1.8 Ga Akitkan and Central Aldan Orogens; the East Antarctica and an unknown continental block were joined by the 1.73–1.70 Ga Nimrod orogen; the South and North Indian Blocks were amalgamated along the Central Indian Tectonic Zone; and the Eastern and Western Blocks of the North China Craton were welded together by the c. 1.85 Ga Trans-North China Orogen. Outgrowth Following its final assembly at c. 1.82 Ga, the supercontinent Columbia underwent long-lived (1.82–1.5 Ga), subduction-related growth via accretion at key continental margins, forming at 1.82–1.5 Ga a great magmatic accretionary belt along the present-day southern margin of North America, Greenland, and Baltica. It includes the 1.8–1.7 Ga Yavapai, Central Plains and