So, very little interesting has happened in my life/work
since my last post so I thought I would use my monthly update to comment on the
perils of being a geologist in public, or more accurately why we should not be
allowed around normal people and rocks at the same time.
At the end of May I went hiking in the Lake District with
UEA’s Fell and Mountaineering Society. (Un)fortunately for them the areas of the
Lakes we visited had such an interesting geology once a couple of people had
asked a few questions, stupidly letting me know they were vaguely interested, I couldn't help myself in commenting in
whatever we were walking over at the time.
Being in the central lakes we were mostly scrambling around
on rocks of the Ordovician (around 450Ma) Borrowdale Volcanic Group; lavas,
ignimbrites and volcano-clastic sediments. These formed at a time when
subduction was closing the Iapetus Ocean and forcing continents together. This triggered
massive eruptions which created a large and very active volcanic island arc as
oceanic crust was forced under the ancient microcontinent of Avalonia (whose
rocks underlie much of England and Wales, Snowdonia formed around the same time
under similar conditions) which was then residing in the subtropical southern
hemisphere. About as far removed an environment as possible to the peaceful
misty mountains that now serve as our only reminders of this violent time.
On the Saturday we climbed Hellvellyn which appeared to be
mostly made up of Lavas, many of which had a very nice amygdaloidal texture –
where the vesicles (holes where gas bubbles solidified) have filled in which
another mineral, often zeolite, to create a distinctive white spotty texture
contrasting the dark lava rock. The term amygdaloidal (from the latin for
almond; amygdale) actually refers to
the stretched shape of the infilled vesicle, created by the stretching of the
original bubble by the flowing viscous lava. I may have explained all this
several times throughout the climb to anyone dumb enough to come up to me with
a, “what’s this, it’s pretty” or similar...and then probably almost instantly
regretting it as I went through an in depth explanation of the formation of
these features.
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| Look, I've found a rock! |
The next day was even worse, I forget the name of the
mountain we went up – some well known scramble route near Scafell – but it was
completely made up of a beautifully preserved ignimbrite, the lithified remains
of pyroclastic flows (deadly currents of superheated gas and ash which can
travel up to 450mph, here's a good compilation video of explosive eruptions with pyroclastic flows and Plinian plumes: pyroclastic flow movie) from explosive volcanic eruptions, which must have been
pretty long lived and catastrophic to produced the hundreds of meters worth we
scrambled through. Having seen recent (well around 200Ka as opposed to 450Ma)
ignimbrite deposits in Tenerife on a field course in my Master’s year I knew
what I was looking at and I was amazed
to see how all the features were still visible after all this time, and the
rocks were still sharp – my hands and knees got shredded. All the classic components were present, from
erosional bases with low angle bedforms, showing discrete eruptional events had
violent pyroclastic flows which ripped up previously deposited layers, to
pumice layers and fine ash with accretionary lapili (concentrically ringed
balls of ash formed as particles roll around in turbulent plumes in phoenix
clouds above the pyroclastic flow) showing fallout from the Plinian plume. How
am I not supposed to get overexcited and point things like this out to people?
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| Ordovician ignimbrite deposits, Lake District |
Now this obviously isn't the first time this kind of thing
has happened, a few weekends ago (when we had the one week of summer) I went to
a beach with a friend. As the sea at Cromer (North Norfolk) didn’t look
particularly inviting we just laid on the beach and ended up playing I Spy (I
may have mentioned how cool I am). Surprisingly she wasn't impressed; it turns
out syn-sedimentary faulting and onlap (in the Quaternary esturine and fluvial
deposits exposed in the cliffs (Norfolk geology)) and even flint are not acceptable things to ‘spy’
if you’re not playing with a fellow geologist. Another time I was walking with
a group of friends (again around the Norfolk coast) who couldn't understand my
interest in the fact that the local council were using huge blocks of some sort
of pyroxene (couldn't get close enough to check which) cumulate as coastal
defences, as far as I know there are no large mafic intrusions around East Anglia
so this must have been brought in from miles away. And on a night out last week myself and a fellow geologist were explaining to the barman the formation processes behind the zoned plagioclase phenocrysts (big white crystals) in the 'granite' bar top, even though it was just a stuck on laminate. Even my holiday photos are
dominated by interesting rock formations.
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| Some nice bedded sandstones, near Macclesfield |
Now what I am wondering is, is it time to get lithophilia recognised
as a real, mental condition so that we can get help (I know for a fact I am not
the only sufferer) or should ‘normal’ people just learn to accept us for who we
are, love rocks and embrace the weirdo who thinks it’s normal to carry a hand
lens around at all times?
