April saw a series of "missions" that
took me outside of my normal haunts, starting
with an appointment in deepest Surrey.....
This was the venue for a filming-session with
BBC1's Countryfile programme as part of the
launch of their 2006 photography competition -
theme = "weather"....
suggested the Devil's Punchbowl by the A3 at
Hindhead as a venue (scenic, easy to reach from
London etc). Wish I could have suggested some
decent weather too! The day dawned misty, chilly
and damp, and remained that way throughout the
filming. Here's the production-team and Jo Brand,
who was being assailed by a variety of artificial
"weather" generated by the
special-effects wizardry. She gets my vote for
being such a good sport!
Why not give this comp a try? Some cool prizes
and good amounts of kudos too. For details of how
to enter, see http://www.bbc.co.uk/nature/environment/programmes/countryfile/photocomp.shtml
A few days later saw me giving a seminar on TORRO
down in Dorset. Gave me chance to have a wander
along one of my childhood stamping-grounds - the
beaches of the Jurassic Coast. Here's a shot of
last winter's landslide at Charmouth...
...while further east this high cliff of grey
marls was not a place to linger beneath. You
can't see the huge crack behind this
several-hundred feet high pillar but I'd give
this section less than 6 months before it comes
That evening took me to Abbotsbury with fishing
gear - I'd heard mackerel were being caught off
Chesil Beach there. This is looking east towards
the amazing beach and the Fleet - the saltwater
lagoon behind it, with both disappearing into the
sea-fog that was gathering in the distance....
Towards sunset I caught a few mackerel and got
bound at last and in late evening I was heading
northwards out of Rhyader when I caught sight of
these mid-level clouds with virga fall-streaks....
...and later on these lenticulars out to the
By the time I got to the top of the pass the sun
had just dropped below the horizon and I lingered
to watch the colours change, deepen and slide
slowly into night....
....this cirrus-field commanded a good bit of
later, underexposed slightly to bring out the
rich colour and silhouette the ground more!
The following weekend I went on a reconnaisance
to the SW tip of the Llyn Peninsula and Bardsey
I'd planned to lead a geological field-trip there
so thought an up-to-date recce would be a good
It's a beautiful area, with Bardsey Island
sitting on the sea across the raging 5 knot plus
todes that pour through this narrow passage - no
place for under-equipped boats!
places here and there for the unsteady! These
grass slopes are a lot steeper than they look and
would be a bit of a horror after rain, ending as
they do in sheer cliffs...
Here's a good reason for visiting this
locality....for scale, there are several anglers
standing at the end of the point R! Can you see
Here is the interesting geology in close-up.
These weird rocks are part of the Gwna Melange,
which forms a lot of the N coast of the peninsula
and also occurs on Anglesey. A melange is a huge,
catastrophic underwater flow of debris. These
white blobs (sorry, masses of quartzite) are
individual fragments of debris - giant boulders
in effect, tens of metres across. Some of these
clasts in other parts of the melange can be over
a kilometre across!
Other clasts include pillow-basalts, banded
charts, algal limestones and red mudstones. The
melange is thought to have originally covered
several thousand square kilometres and it is
believed to have formed at a destructive
plate-margin where an ancient sea-floor,
including volcanic islands where shallow-water
sediments were deposited, was being subducted
under North Wales in a south-easterly direction.
Big debris-flows are commonly found at subduction
I like the description of the famous geologist
Edward Greenly though. Greenly mapped Anglesey in
the early part of the 20th Century and described
the Gwna Melange as "quite
Agewise it was thought to be late Precambrian
although certain poorly-preserved microscopic
fossils have been found which suggest it is of
Cambrian age. Either way, it remains an enigmatic
- and spectacular - deposit!
...So, farewell to Bardsey and high hopes for the
same glorious weather on my guided trip a couple
of weeks later!
A couple of weeks later! This is the village of
Porth Dinllaen near Nefyn in the northern Llyn.
Blazing sunshine over Snowdonia - what had I done
to deserve this?
Low pressure sat over E England was responsible.
Warm air in the low's circulation was drifting
out over Liverpool Bay and being cooled by the
chilly Irish Sea to the point that the moisture
it contained was condensing out as fog and then
drifting back onto land. Sea-fog on a supposedly
scenic geological trip - aaaargghhh!
the geology at Porth Dinllaen is still good
whole headland is a raft of pillow-basalts -
another giant clast within the Gwna Melange it is
thought, and probably correlated with the famous
pillow-lavas of Newborough on Anglesey. These are
superb examples though!
What happens when lava is erupted underwater is
that it cools rapidly. These pillows form when
the molten lava breaks through the thin walls of
underwater lava-tubes. It then squeezes out like
toothpaste into the water and quickly solidifies
as these irregular, tongue-like protrusions. The
process repeats itself time and again, so that
the resulting protrusions stack one upon another
as the undersea lava-flow advances along.
The red stuff between the pillows (which
incidentally are typically half to one metre
across) is jasper, formed by the precipitation of
silica and iron from hydrothermal fluids expelled
from the volcanically active sea-bed.
Back down SW, meanwhile, the sea-fog won the day.
Only after my field-party had departed did even a
fraction of Bardsey Island start to show itself!
The same party got attacked by an afternoon
thunderstorm on their second day out. Two fairly
unusual weather-phenomena (for Wales) in two days
- that IS bad luck!
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