Lava fields – old and not so old
The volcanoes which were active when the northern granites formed and the central complex erupted were not the only ones to affect the region. On at least five earlier occasions, volcanoes erupted and left their mark. The most widespread formed in the Carboniferous period, as part of a vast area of volcanoes which stretched to the Campsies north-east of Glasgow and beyond. Time and again large fissure volcanoes flooded the area with basalt lavas building up a pile many hundreds of metres thick. The south end of Bute and almost all of Little Cumbrae have ‘trap featuring’. A few of the lavas reached Arran where they can be seen on the Corrie shore.
Other volcanic episodes left lavas and ashes on Arran; these are associated with both the Old and New Red Sandstone and Carboniferous rocks. The very oldest lavas are of the Ordovician age. These pillow lavas erupted under water, providing evidence that the area was covered by an ocean at that time.