By way of comparison, the Peterborough Petroglyphs in Canada...
At Petroglyphs Provincial Park you see one of the largest concentrations of petroglyphs in North America, and a few look an awful lot like a Viking vessels!
http://www.canadacool.com/location/petroglyphs-provincial-park/
The origin of Mythical Ships
http://www.native-science.net/Ship.Mythical.htm
Swedish petroglyphs — looks like Viking-era ships to me:
http://www.visitsweden.com/ImageVault/Images/id_375/conversionFormat_13/scope_0/conversionFormatType_Jpeg/ImageVaultHandler.aspx