User Comments
Not a geologist, Andy, but is it dolerite? I used to climb lots at Hadrian's Wall and the dolerite there looks very different, black and columnar. Would it be a volcanic rock like rhyolite or andesite?
Lankyman - 01/May/20
I'm not a geologist either, but unless the guidebooks for the area are wrong this is definitely dolerite - the same kind as at Tremadog, rather than the more basalt-like columnar form. Though it feels close to gabbro in texture!
Andy Moles - 01/May/20
Ah, gabbro. I think I read somewhere that dolerite and gabbro are chemically the same, they just form at different depths. Or maybe I'm confused with basalt or just plain confused?!
Lankyman - 01/May/20
Basalt, dolerite, gabbro, essentially they're all made from the same volcanic stuff, just formed differently according to rate of cooling and probably other factors. One thing I've learned about geology is that any facts I think I know, the reality is more complicated.
Andy Moles - 01/May/20
I am a geologist and I would say that, at a distance (which is always a bit dodgy) that looks like a typical dolerite, of the kind that outcrops in Snowdonia, e.g. at Tremadoc and the wings of Dinas Mot in the Pass.
John Stainforth - 03/May/20