Wednesday, 28 September 2016

Big skies at the Big Strand

What looked likely to be a washout turned into a lovely walk under blue skies along the Big Strand on Sunday for our last rAmble of the season. Our group of three (we who don't take any notice of the weather forecast ;-D) set off along the beach toward Knockangle Point to see what we could find, and we weren't disappointed.
Sunshine after the rain

Under the big blue sky
The best part (besides the cake at the half-way point) was looking through all the tiny shells to be found on the rocky shore, including Arctic and European Cowries, Sting Winkle, Hungarian Hat and Tortoiseshell Limpet (to name but a few!). The range of colours and shapes is incredible - if you've never sifted though a seashore of shells, I'd highly recommend it :-D



More treasures
A very pleasant afternoon's stroll in good company - looking forward to next season's rAmbles already!

Wednesday, 21 September 2016

Snowball Earth rAmble at Port Askaig and Bunnahabhain

Another rainy geological walk. Five hardy souls braved the weather to join Dave to look at Islay's classic 'snowball earth' deposits. First up was the world-famous Port Askaig Tillite - a sequence of silty rocks with a large number of varying sized 'stones' - mainly of granite - embedded in it. Dave explained the two competing theories about its origin: either it was deposited on land as a melt-out of an ice sheet (or a series of ice sheets) or it was deposited in the sea from dirty floating ice. We looked at some alleged 'dropstones' near the lifeboat station - it could be that these did in fact drop off the base of the floating ice and penetrate into the sediment - or that the laminations wrapping around the stones are diffracted cleavage planes (i.e a later metamorphic event).

The jury is still out, but nevertheless there is a considerable thickness of undoubted glacial deposits which are about 650 million years old and it is possible that they correlate with similar deposits in other parts of the world and - if they are of the same age - they could be evidence that the Earth was indeed entirely ice-covered. Again the jury is still out because we can't date these tillites here very accurately but we do think that Islay was probably in the tropics at this time so so much ice deposit would be unusual!
Then onto Bunnahabhain to look at the Bonahaven Dolomite - a sequence of carbonates that overly the Tillites and are purported to be a 'cap carbonate' which is quite typical of these glacial deposits in other parts of the world and are believed to be evidence of dramatic changes in ocean and atmospheric chemistry as the world recovered from the snowball event. The rocks contain stromatolites - evidence of bacterial activity in (probably) warm water - ie the usual conditions you'd expect in the tropics - they were the coral reefs of their day (before corals were invented!).
Then back to Dave and Isobel's van for lashings of tea, ginger cake and whisky to warm us up!

Wednesday, 7 September 2016

A pleasant Ardnave rAmble 4th Sept

It was a lovely afternoon, gone the morning showers and a bright afternoon unfolded, perfect for a Sunday rAmble.  9 enthusiastic visitors keen to explore.  We marvelled at the scenery, Loch Gruinart had been emptied of the sea and the distant haze of cloud gradually lifted through the walk. We stared out viewing north east to the islands of Jura and Scarba, Oronsay and Colonsay were in plane view, the sun shining brightly on the farmhouse on Oronsay.  Mull gradually became visible and to the north west the lighthouse of Dubh Artach.

Our aim was primarily birds, and the chough flock did not disappoint, about 25 birds in a loose flock probed the dune slopes and searched through cow pats.  A look over a  well worked pat revealed large juicy dung beetle larvae, perfect chough food.  We were able to get good views through the telescope and clearly see their red legs and bills, and their scolding calls highlighting their presence.

A pair of Buzzard soared over the cliff on Knave Island and the song of seals could be heard and on closer scanning we saw many hauled out on the low tide rocks west of the island. A Great Northern diver was spotted flying high.  During our walk back we took in the neat beauty of a couple of Wheatear and a Skylark only a couple of meters away oblivious or just not bothered by our group on the path ahead.

Birds: Chough (c.25); Raven; Starlings; Gannets; Great Northern diver; Skylark; Meadow Pipit; Shag; Greylag Geese; Buzzard; Wheatear; Oystercatcher

Flowers: Grass of Parnassus; Self Heal; Ragged Robin; Autumn Hawkbit
Mammals: Seals (Grey/Common); Hare; Rabbits (lots of Myxamatosis)

All in all a pleasant walk in pleasant company.
Fiona MacG

Our next Sunday outing takes us on a Fungi Foray with Alistair to Skerrols Loch, Bridgend.