Endless basalt lava was formed for millions of years.
This basalt lava we can now find at east Greenland, Faroe Islands, north Ireland and west Scotland even it was all formed where Iceland is now.
13.000 to 10.000 years ago Last cold period of the Ice Age did end some 10.000 years ago and our warm period of the Ice Age started.
The ice started to melt some 15.000 years ago and some part of Iceland was without ice some 13.000 years ago.
Then the oldest lava fields in Iceland were formed in eruption in the Reykjanes peninsula.
Some 9000 years ago the big glacier was fully melted and Iceland was without glaciers until some 2500 years ago when glaciers started to form on highest mountains.
So at some time-point the sea manage over the land-bridge between Scotland and Iceland and then later on the sea manage as well to cut the land-bridge between Iceland and Greenland. Lot of animals was then trapped on the island and needed to settle.
It was possible to hike from Scotland to Greenland over the basalt lavas formed with endlessly eruption over the hot spot and where Iceland is now.Lot of animals was using this land-bridge and saying hello to the place where Iceland is today.20-30 million years ago Because the drifting of the continents, because the new ocean floor formed constantly at the Atlantic mid ocean ridge the distance between Greenland and Scotland was getting longer and longer every year ... And 3 cm per year is about 300 kilometers in 10 million years. We do not know when this happened but most likely some 20 or 30 million years ago.About 70 million years ago Greenland was south east from Iceland or at least south east from where Iceland is now.Even Iceland is the best place in the world to see where two continental plates are formed and drifted to both sides ... Greenland was moving slowly to North West and drifting over the hot spot that is under Iceland.
An extended discussion on Iceland's history and prehistory until the present time.