Around 50 to 60 million years ago , during the Paleogene Period , Antrim was subject to intense volcanic activity , when highly fluid molten basalt intruded through chalk beds to form an extensive lava plateau .
Some 50 to 60 million years ago , during the Palaeogene period , Antrim was subject to intense volcanic activity , when highly fluid molten basalt intruded through chalk beds to form an extensive lava plateau .