ANOTHER AGE

I am referring to your Cosgrove hotspot article ( Out of the fire, AG 156), in which a link between the great number of remnant volcanic outcrops was established in the so-called Cosgrove Track, which seems to bring into line a volcanic chain from Hillsborough right down to Cosgrove in Victoria without including the massive and spectacular complex of the Glass House Mountains. Are the latter of a different geological age, or for what other reason was this complex excluded? I would be grateful if you could elaborate. BERT HEROLD, BRIBIE ISLAND, QLD

ED: According to our volcano expert, Professor Rhodri Davies, the Glass House Mountains form part of another age-progressive track: a 770km-long track that extends from Fraser Island in Queensland to Comboyne in New South Wales, displaying a record of volcanic activity from 32mya to

16mya. It is likely to be the surface manifestation of another mantle plume.