Comparisons of the 2005 Geologic Map of North America with the 1965 Map, Areas 1-4
3. Iceland and parts of eastern Greenland
- Although the general distribution of rock types in Greenland (A) on the new map is similar to that on the 1965 map, the undivided Precambrian rocks shown on the old map are subdivided to distinguish Archean gneiss, sedimentary and volcanic rocks, and Middle Proterozoic gneiss, sedimentary and volcanic rocks, and mafic plutonic rocks. Rocks formerly shown simply as Tertiary volcanic rocks are now identified as Paleogene mafic volcanic rocks.
- The geology of Iceland (B) is also rather similar on the two maps, but more precise ages for the volcanic rocks are given on the new map, and volcanoes, calderas, and faults, none of which were depicted on the old map, are shown on the new.
- By far the most significant change in this part of the new map is the addition of seafloor features including the spreading centers along the Kolbeinsey (C) and Reykjanes (D) Ridges, both parts of the Mid-Atlantic Ridge System, and the oceanic crustal isochrons (E) that record the history spreading across these ridges as Greenland separated from Eurasia during the Tertiary and Quaternary. The connection between the spreading centers and the faults and volcanic edifices in Iceland also is obvious.
Return to comparisons of map areas 1-4.
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