These cliffs are the edges of the great layers of basalt which the volcanoes of the ocean bed deposited in the Tertiary period, about 60 million years ago.
(These cliffs; are; the edges of the great layers of basalt) (the great layers of basalt; deposited; T:in the Tertiary period; T:about 60 million years ago)
These cliffs the great layers of basalt
are deposited
the edges of the great layers of basalt
T:in the Tertiary period T:about 60 million years ago