Arctica or Arctida was an ancient continent which formed approximately 2.5 billion years ago in the Neoarchean era. It was made of Archaean cratons, including the Aldan and Anabar/Angara cratons in Siberia and the Slave, Wyoming, Superior, and North Atlantic cratons in North America. Arctica was named by Rogers 1996 because the Arctic Ocean formed by the separation of the North American and Siberian cratons. Russian geologists writing in English call the continent "Arctida" since it was given that name in 1987, alternatively the Hyperborean craton, in reference to the hyperboreans in Greek mythology.