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Baltica is an ancient continental block associated with the core of northeastern Europe. In paleogeographic reconstructions it is treated as a coherent unit over specified intervals, using the surviving rock record rather than present political boundaries to define its identity.

Paleomagnetic poles, ages of deformation and correlations between rock sequences constrain its past position and relation to Laurentia and other continental blocks. Agreement between several independent indicators is stronger than a visual fit of coastlines. Reconstructed arrangements remain hypotheses with stated age ranges and uncertainties; the modern position of Baltica does not determine its ancient orientation.

Laurentia is the ancient continental core underlying much of present North America and Greenland. Its old, mechanically persistent crust allows geological observations from different regions to be combined into a history of continental assembly and motion.

Paleomagnetism constrains past latitude and orientation, while matching geological ages and structures helps test connections to other blocks such as Baltica. A paleocontinent is therefore a reconstruction from preserved physical records, rather than a claim that every part of a modern continent shared one uninterrupted history. Younger accreted margins must be distinguished from the older core.

Ross N. Mitchell studies ancient continental configurations using paleomagnetism and the geological record of supercontinents. In a 2011 paper with David A. D. Evans, he combined dated magnetic-pole records with tectonic and stratigraphic correlations to reconstruct the core of Nuna. The reconstruction fitted the Siberian craton, Laurentia and Baltica together for an interval roughly 1.9–1.3 billion years ago and tested that fit against the histories of their margins.^[ref]

This is a comparison between several kinds of evidence. Matching apparent polar wander paths constrains relative continental motion, while dated evidence of mountain building and continental-margin histories test whether the proposed neighbors experienced compatible events. Divergence between those records can indicate assembly or separation. The paper presents a particular reconstruction to be tested against further observations; its detailed fit is not implied merely by naming a supercontinent.

A researcher in paleomagnetism and supercontinent histories. Institutional profile: igg.cas.cn/sourcedb_igg_cas/cn/zjrck/yjy/201912/t20191219_5460988.htm

The Siberian craton is an ancient, long-lived continental block in northern Asia. Its comparatively stable interior preserves a record that can be used to reconstruct earlier continental configurations, distinct from younger tectonic belts around its margins.

A reconstruction combines dated rock units, structural relationships and paleomagnetic poles. The poles constrain latitude and orientation within a magnetic-field model but generally leave a longitude ambiguity. Consequently, placing the Siberian craton relative to Laurentia or Baltica requires additional geological evidence; a single magnetic direction cannot uniquely determine a complete ancient world map.