Answer from reality: the igneous rocks of Scotland (where volcanism no longer occurs) are much much older than the sedimentary rocks of south eastern Britain.
'Answer' from 'Answers in Genesis'? They must all be of approximately the same age - or perhaps the igneous rocks might be 'younger'!https://answersingenesis.org/missing-li ... k-problem/
"The majority of rock layers that contain fossils are sedimentary rock layers from the Flood of Noah’s day about 4,350 years ago ... Of course, there are rock layers that have formed since the Flood, due to local floods, volcanic eruptions, and so on. But most of the layers in question formed in the Flood."
So igneous rocks - even the very old ones in places such as Scotland where any volcanoes are undeniably extinct and there has been no volcanism recorded in the past 4,350 years - MIGHT have formed SINCE the flood of Genesis (which would 'account' for the lack of evidence of them having once been totally submerged).
Of course massive floods of short duration or very long periods of being submerged under higher sea levels do NOT form igneous rock layers (and contrary to YEC claims the Bible says nothing specifically at Genesis 7:11 about massive volcanism during the build-up of the flood of Noah with its surging waters from both above and below). Floods and rising oceans lay down sediments ie sedimentary rock layers.
Actually I could find little on the AiG website about the rocks of Scotland (and I have not searched other YEC sites).
However, I did find THIS article about the Devil's Tower in Wyoming USA (an igneous intrusion or laccolith where as far as I know there is no record of any current or recent volcanism):https://answersingenesis.org/geology/na ... n-wyoming/
I'm assuming that their 'biblical explanation' of its formation might also apply to (ancient) igneous rocks found in Scotland.
That 'explanation' being: "Since creation took place around 6,000 years ago, according to the Bible, Devils Tower could not have formed millions of years in the past. One catastrophic event could be responsible for the formation of this natural wonder. This event was the Genesis Flood about 4,500 years ago, as recorded in Genesis 6–9. There is evidence that dramatic volcanic activity accompanied the Flood, which would explain the intrusion of magma that initially formed Devils Tower underground. It is also likely that the earth’s surface was dramatically changed as the crust of the earth shifted..."
Thus I deduce that IF pressed AiG would declare that the igneous rocks in Scotland were either formed at the SAME TIME as the sedimentary rocks of say the Cotswolds or South Downs - or perhaps they might even have been formed more RECENTLY (before the area became volcanically inactive and former volcanoes became extinct).
Another result for biblical creation science.