#5 Geology near my home or lab

[kaberett]

Honestly? I live in a sedimentary pseudo-basin, so to me the most exciting things are the building stones. Which -- don't get me wrong! There's some lovely ones! There's a garnetiferous marble used to face this one building, which has streaks of tiny garnets pressed into waves and curls and it's great. There are also My Favourite Kerbstones, full of great big semi-aligned plagioclase laths; and lots of nice labradorite granites.

Much more interesting is the coast around the Mouldering Ancestral Pile: the beach a five minute walk away (Polurrian) features an outcropping of the Lizard Boundary Fault - the join between continental and oceanic crust. And then there's the Lizard complex as a whole, wherein what-used-to-be-the-mantle is actually exposed at the surface - over a few miles of coast you can actually walk from the base of old oceanic crust up to the surface, through gabbroic cumulates and sheeted dykes and pillow basalts; you can literally stand on an exposure of the Moho-that-was, the boundary between crust and mantle, and it's really cool. SO: for these purposes, Cornwall is home much more than London is. ;)

Comments

[khronos_keeper]

Holy shit I got chills reading your description. I never thought of walking a piece of the earth from millenia ago.

[kaberett]

Millions of years even. It's kind of astonishing. The lump of meteorite on my desk - which I actually get to pick up and touch, wtffff - is about four and a half billion years old, and it's just... mind-blowing. Geologists mostly compensate by deciding that anything that happened in the last five million years is "recent" and skewing our perceptions that way.

[catyak]

We took Kit to see a bit of the local geology, he got to stand on the Hayward Fault. It was one of those places where the kerb stones are displaced by a few inches due to the slippage. Of course, if it does a proper job, such as is predicted in the next few years, it's probably going to displace more than the width of the road.

[wordweaverlynn]

I am still incredibly thrilled to be living in a place I learned about in my college geology class. Hayward is geologically famous.

[frayadjacent]

I spent a week in Exeter last Northern hemisphere summer (visiting the Met Office, hello there disciplinary neighbor!), and got to walk a bit of the Jurassic coast. It was so exciting! I kept imagining I saw fossils but I don't think I did, hee hee. It felt very cool to be walking not just in geologic history but in the history of geology as well.

[kaberett]

heee :-) yes. That is one of the lovely things about Traditional Undergrad Field Trips.

[shadowspar]

Oh hey, this reminds me! I'm often pretty focused on what we lack up here in Northern Ontario, but, y'know -- rocks are a thing we have. ^_^

[kaberett]

Thank you :-)

[davidgillon]

you can literally stand on an exposure of the Moho-that-was

Ha, who need the mohole when you have Cornwall!

Edited to add: actually this is sort of how I feel when back in Durham and we head up Weardale and over into Teesdale and encounter bits of the Whin Sill and the Sugar Limestone up near High Force and Cauldron Snout (for non-geologists/northerners, the Whin Sill is a volcanic intrusion underlying most of the North East - those shots of Hadrian's Wall running along a precipice are its northern edge, and sugar limestone is what you got when it cooked the local limestone in Teesdale - it's about as robust as the name sounds). My living room clock is a slice of Weardale limestone with galena 'numbers' I picked up in a souvenir shop on one of those trips. Geology as invocation of home.

Mantle Hillness

[hairyears]

I didn't know that the mantle was visible anywhere!

I wonder if anyone's written a 'Geology guidebook for walkers' for the Lizard...

Re: Mantle Hillness

[kaberett]

So the actual mantle (as opposed to "fossilised mantle", which is what ophiolites are) is technically visible at super-slow spreading mid-ocean ridges (half-spreading rates less than 2mm per year); the South-West Indian Ridge is one example. Basically what's going on is that you've got two plates separating so slowly that the mantle being sucked up has time to cool conductively so never melts - you just get it sort of smearing very gently across the top of the plates, and it's really weird.

Strata Motor

[hairyears]

I wonder if this could be made into a DW icon:

[inoru_no_hoshi]

Oooo. I knew the Cornwall coast was gorgeous, geologially speaking, but that is way more geologic history than I realised! Also now that is a place on my list to visit should I ever go to the UK. :D