BeskrivelseNorth america and scandinavia basement rocks.png
North Americancratons and basement rocks. As radiometric ages were determined for the shield-like rocks on the continents which were either exposed at the surface, underlay the flat rocks, or were within the interior of the mountain belts, patterns of age intervals were determined. These old rocks have been called the "basement". This has been interpreted to mean that the continents had somehow grown by development of rock assemblages with these characteristic age parameters. The expanding continental nuclei are part of the "craton" which consist of both exposed and buried basement rocks.
This is a retouched picture, which means that it has been digitally altered from its original version. Modifications: Change of colours to match some geological map colour templates. The original can be viewed here: North america basement rocks.png: . Modifications made by Bjoertvedt.
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2005-09-16T15:47:59Z Saperaud 484x429 (13371 Bytes) [[North America]]n [[craton]]s and basement rocks. As radiometric ages were determined for the shield-like rocks on the continents which were either exposed at the surface, underlay the flat rocks, or were within the interio
{{Information |Description=North Americancratons and basement rocks. As radiometric ages were determined for the shield-like rocks on the continents which were either exposed at the surface, underlay the flat rocks, or were within the interior o