Pete Bowden
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peterlbowden1.bsky.social
Pete Bowden
@peterlbowden1.bsky.social
380 followers 150 following 150 posts
Mylonites, migmatites & metamorphism. With some pseudotachylite thrown in for light relief.
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peterlbowden1.bsky.social
We haven't established enough windbreaks yet and our fruit trees are still young.
Storm Floris stripped our outdoor beans and spuds😱
August 25, 2025 at 5:16 PM
peterlbowden1.bsky.social
One of my favourite Scottish mountains with fantastic Dalradian geology on the northern flanks.
The snow covered triangular peak of Schiehallion on a bright spring day.
July 15, 2025 at 5:17 PM
peterlbowden1.bsky.social
I knew if I kept watching your posts for long enough I would get an identification for these beautiful flowers spotted near Mealasta slipway😀
Bright yellow flowers amongst the grass on the headland north of Mealasta slipway, west coast of the Isle of Lewis. Look like the Bog Asphodel, (Blioch in Gaelic), in a recent post by Frank Rennie.
July 11, 2025 at 5:46 PM
peterlbowden1.bsky.social
Lewisian meta basic/ultrabasics showing similar shear zone fabrics can be seen on the west coast of the Isle of Lewis.
The contrasting colours of the feldspars and mafic minerals really emphasise the strain variations🤓.
I haven't seen any of the thin discreet shear zones yet, but I live in hope😉
A grey meta gabbro shows speckled appearance towards top of the photo. The minerals become elongate and to define a curved tectonic fabric which becomes smeared out in a shear zone seen in the lower part of the photo. Seen on the west coast of the Isle of Lewis.
July 10, 2025 at 2:29 PM
peterlbowden1.bsky.social
In a land of "Undifferentiated grey gneiss" the occasional dun coloured outcrop is much appreciated😉⚒️.
@earlyearthtim.bsky.social for scale, at Maraig, Isle of Harris.
Brown and dun coloured outcrop of meta-ultrabasic, Maraig, Isle of Harris.
June 6, 2025 at 4:43 PM
peterlbowden1.bsky.social
When viewed from this, (opposite), side the large #FridayFold resembles a rock formation seen in the #MonsterHunterWilds computer game. ⚒️🧪
Large open fold in grey and brown Lewisian gneiss contorts the foliation. The outcrop resembles a rock formation seen in the "Monster Hunter Wilds" computer game
May 30, 2025 at 12:20 PM
peterlbowden1.bsky.social
Not really my field, but can't resist taking photos of sedimentary processes, especially where there are sufficient heavy minerals to emphasise the features.
This is also about a metre across.
Small tributary stream building a delta into larger brown, (peat stained) stream. The sedimentary features observed in the yellow sand are emphasised by black heavy mineral concentrations.
May 13, 2025 at 4:34 PM
peterlbowden1.bsky.social
Not usually an admirer of lichen as they obscure the geology, but these eye catching colonies bear testament to the fine air quality here in the Outer Hebrides.
🧪⚒️
Pale brown to fawn coloured polygonal shaped lichen colonies covering an outcrop of Lewisian gneiss on the Isle of Grimsay in the Outer Hebrides. The units are generally between 5mm and 15mm. Pale brown to fawn coloured polygonal shaped lichen colonies covering an outcrop of Lewisian gneiss on the Isle of Grimsay in the Outer Hebrides. The units are generally between 5mm and 15mm.
May 12, 2025 at 4:35 PM
peterlbowden1.bsky.social
Live from the field, #FridayFolds on Berneray, Outer Hebrides.
Sheared Lewian gneiss.
Waiting for tide to go out 😎
Banded black, grey and white gneiss shows minor S shaped folds in sheared Lewisian gneiss. Berneray, Outer Hebrides.
April 18, 2025 at 10:16 AM
peterlbowden1.bsky.social
What a coincidence, just sent email last night, to council archeologist, about similar occurrence on Baleshare.
Think it may have been uncovered by the winter storms.
Similar finds nearby were previously excavated.
April 18, 2025 at 6:57 AM
peterlbowden1.bsky.social
A beautiful example of an Outer Hebrides dyke cutting the foliation in Archaean #Lewisian gneiss. Although folded by later Laxfordian deformation both the dyke and a thin apophysis exhibit near perpendicular angular discordance in the fold hinge, becoming concordant in the limbs.
Isle of Harris. ⚒️🧪
A black Outer Hebrides dyke cuts across the pre-existing foliation in grey Archaean Lewisian gneiss. Thin apophysis (offshoot) and the hinge zone of the folded dyke exhibit near perpendicular angular discordance to the foliation. These rocks were folded during Laxfordian deformation and strong flattening in the limbs of the folds brought the contact of the dyke and the foliation into concordance. This outcrop is located west of the village of Rhenigidale, Isle of Harris, Outer Hebrides.
February 3, 2025 at 12:11 PM
peterlbowden1.bsky.social
A #FridayFold fresh from today's first field excursion of the new year.

The black Outer Hebrides Basic dyke was intruded into the paler grey Archean Lewisian gneiss prior to Laxfordian deformation which produced the tight recumbent fold.

Near Rèinigeadal, (Rhenigidale), N. Harris, Outer Hebrides.
Black Outer Hebrides Basic dykes were intruded into the paler grey Archean Lewisian gneiss prior to Laxfordian deformation. At this location the deformation produced tight recumbent folds especially in the darker rocks. Approximately 0.5km south west of the village of Rèinigeadal, (Rhenigidale), N. Harris, Outer Hebrides.
January 31, 2025 at 5:02 PM
peterlbowden1.bsky.social
Interesting barometer reading this morning as storm Éowyn passes by😵. Adjusting for elevation of 67m this is equivalent to approx. 948hPa at sea level.

I think I might set it to show sea level equivalent in the future.
January 24, 2025 at 12:56 PM
peterlbowden1.bsky.social
My OH is a keen walker and getting quite good at photographing interesting geological locations. This has gone to the top of my Spring excursion list.

Pink #Laxfordian granitic intrusions invading #Lewisian gneisses and amphibolites.

Mangersta, #IsleofLewis ⚒️🧪
Tall grey cliffs being battered by a rough sea. Older grey Lewisian gneisses and black amphibolites are intruded by salmon-pink granitic pegmatites and aplites of Late-Laxfordian age. The cliffs are located near the Mangersta bothy on the west coast of the Isle of Lewis, Scotland.
January 23, 2025 at 12:46 PM
peterlbowden1.bsky.social
Walks on Boxing Day have become a lot more interesting since moving to the #IsleofLewis
Grey and pale green banded rocks (mylonitic gneiss) contorted by folds and sub horizontal thrusts. Traigh Shanndaigh near Ness, Isle of Lewis.
December 27, 2024 at 10:49 AM
peterlbowden1.bsky.social
Spot the refolded isoclinal #FridayFold.

Traigh Shanndaigh near Eòrapaidh (Eoropie), #IsleofLewis

⚒️🧪 #Lewisian #Geology
Predominantly grey rock has yellow coloured bands and porphyroclasts picking out a mylonitic fabric which has been repeatedly folded. Early isoclinal folds, with near parallel limbs, have been tightly tightly refolded. The southern end of the beach has some of the best folding I have seen, (when not obscured by sand). The beach, Traigh Shanndaigh, near Eòrapaidh (Eoropie) is located at near the top (northern end) of the Isle of Lewis and faces the Atlantic.
December 13, 2024 at 10:34 AM
peterlbowden1.bsky.social
Traigh Iar, Udal, North Uist, Outer Hebrides
A deserted sweeping bay with pale sandy beach backed by high sand dunes covered in Marram grass. The sea is dark turquoise to Prussian blue in the sunlight.
November 28, 2024 at 1:14 PM
peterlbowden1.bsky.social
Makes a great display area😍

My local library is really gneiss
A selection of books is displayed on a large slab of grey and pink Lewisian gneiss situated in the centre of Stornoway public library. The large block was sourced from a local quarry and has some cut and polished surfaces which show the tectonic foliation and some minor folds. A pink pegmatite vein in the centre of the top surface cuts across the gneissic foliation.
November 24, 2024 at 5:16 PM
peterlbowden1.bsky.social
There are many larger folds in the #Lewisian gneisses around Cunndal Bay, #IsleofLewis, but these #FridayFolds are the best exposed, (cleanest) I've seen, so far.
⚒️🧪 #Geology
Banded grey Lewisian gneiss with some thicker layers of white or pink granitic pegmatite and black amphibolite show complex folding. In some cases the folds are affected by shearing. The outcrop is well exposed and clean, having been wave washed to keep it clear of surface algae/shellfish/seaweed. The compass-clinometer scale is 15cm long.
November 22, 2024 at 10:48 AM
peterlbowden1.bsky.social
The sea cliffs on the west side of the #IsleofLewis provide some spectacular cross sections through #Lewisian gneisses.

I guess I'm putting a drone at the top of my Xmas list.
⚒️🧪 #Geology
A spectacular seascape on the west coast of the Isle of Lewis with waves breaking on rocks at the base of high cliffs. The grey and pinkish grey Lewisian gneisses show complicated folding and faulting, often offsetting dark grey to black Outer Hebridean dykes, (also Lewisian in age these were formerly called Scourie dykes).
November 19, 2024 at 10:31 AM
peterlbowden1.bsky.social
At the other end of the strain spectrum it becomes really difficult to identify these banded rocks as originally being pillow lavas😉

⚒️🧪 #Geology
Alternating thin black, grey and pale brown bands are disrupted by a shear zone along the axial plane of a fold, (scale is approx. 15cm long). These pillow lavas are so severely flattened that it is almost impossible to identify the original pillow structures. Found in a Svecofennian greenstone belt, located on the island of Kumlinge in the Åland Islands, Finland.
November 17, 2024 at 1:22 PM
peterlbowden1.bsky.social
Yesterday's post showed flattened pillow lavas crumpled by late stage minor folds.
@callanbentley.bsky.social asked if there are less deformed rocks nearby which show they are indeed pillow lavas.

Indeed there are😍
⚒️🧪 #Geology
A clean coastal exposure shows irregular ellipsoid pillow lavas. The pillows are grey to greenish-grey in colour, occasionally there are fawn - pale brown rims. The pillow shapes are often emphasised by the contrasting dark-grey to black interstitial material between the pillows. The outcrop is approximately 2m. wide towards the top of the photo. These basic volcanic lavas form part of a mixed sequence of supracrustal rocks in a greenstone belt of Svecofennian age. Located on the northern coast of Kumlinge, Åland Islands, Finland.
November 16, 2024 at 9:24 AM
peterlbowden1.bsky.social
This was the first geological photo I posted on Twitter back in January 2021.

#FridayFold Small scale folding of flattened pillow lavas, (scale approx. 8cm long). Svecofennian greenstone belt, Kumlinge, Åland Islands, Finland.
⚒️🧪 #Geology
Alternating black, grey and pale brown bands are crumpled by small scale folding (scale is approx. 8cm long). These are severely flattened pillow lavas in a Svecofennian greenstone belt. located on the island of Kumlinge in the Åland Islands, Finland.
November 15, 2024 at 7:27 AM
peterlbowden1.bsky.social
The volcanic features on the Fife coast include this fine example of a basalt dyke intruded into volcanic tuff.

The en-echelon disposition is picked out by the lichen which favours the basalt dyke.
⚒️🧪
A dark grey basalt dyke is covered in pale greenish grey lichen with occasional patches of yellow lichen . The dyke cuts through green unbedded volcanic tuff containing fragments up to 25cm in diameter. The dyke exhibits an "en-echelon" arrangement where it pinches out and then continues with a slight offset. Scale is 150cm walking pole (to left of dyke). This location is very close to the coastal path below St Monans church.
November 13, 2024 at 10:46 AM
peterlbowden1.bsky.social
I found a Rapakivi granite cobble at Leven in Fife. After much discussion it was suggested that as well as the possible "brought by glaciers" explanation, it might have come from Scandinavia as ballast in a Viking boat.
November 12, 2024 at 11:47 AM