Basalt pillow lava, Cornwall

When basalt lava is erupted into the sea, rounded pillow shapes form. Click on the video below to see pillow formation.

These 400 million year old pillows must also have been formed by under-water volcanic eruptions, showing that, during the Devonian Period, this part of southwest England must have been under water. Other evidence shows that Cornwall lay in deep water, whilst parts of south Devon formed shallow coral reefs with a coast further north.