Strabandra Knap Blowhole Cave

A seacave system with a 48m long, 7-12m wide and subtidal main tunnel which is fully dark in its side tunnels. It has 3 active blowholes out of the 6 visible from outside. In addition, the south entrance (see separate entry) was observed to be an active blowhole at 09:45 on 25 Nov 24. The other three blowholes were intermittently active at the same time.

The main tunnel is straight, facing 080 (E by N). It has 3 south going branches, approximately 030 to the main tunnel, with 1 & 3 easily navigable; S1, the eastmost, has a chamber with a pebble beach, towards its S end. A rift tunnel continues for 16m until it comes to a south entrance at NO 88053 83256, on the S side of Strabandra Knap.

S1 starts at 32m down the main tunnel. On the right, there is a north chamber which shares 16m of its S width with the main tunnel and goes 40m or so a bit E of N, eventually narrowing to 3m. There is a rift tunnel at the NW corner which runs another 24m N, ending in a narrow pebble beach. The N chamber has vertical walls and a fairly planar ceiling - unlike the other tunnels which are triangular in section. It is also the tallest part of the system.

S2 and S3 share a short section off the SW end of the main tunnel/N chamber before dividing for 20m or so around a fairly narrow dividing wall. They then join in a chamber which is a pebble beach at low tide, before continuing separately S2 for another 7m, and S3 for 14m. This S2+3 chamber is wide enough to comfortably turn a 5.5m kayak around in.

It is used by seals in calm weather. Only the lower 3 blowholes have a clear view connection to sky viewed from inside. It is unknown whether or not the higher blowholes connect to the main tunnel. There is a straight tube-like connection from just W of the bottom of blowhole #2 which goes up and W to meet blowhole #3 tube. See side elevation at p30) below.

The entrance appears wider under water than above. Depth at entrance is about 5.9 m BCD. Height at entrance 5.9 m ACD.

Notes: The blowholes have been filmed during a moderate gale from ESE. Several such videos are available on Youtube. Careful watching of these reveals that what goes on inside must be quite complex, since the three blowholes rarely spout together - even #1 and #2, whose lower openings are about 0.5 m apart!

S2 was reported to be kayak navigable nearer low low tide than in the photos below to N Feilden by a member of NE Sea Kayakers 11/12/24.

Access: By sea; small boat in main and N chamber; kayak only in S tunnels. Nearest launch point is Stonehaven harbour. Best in bottom half of tide as there may be shortage of headroom at top of HWS. Not safe if any appreciable swell from ESE to N. Light needed for side tunnels.

It is possible to get to the main tunnel entrance by land below half tide on a calm and dry (otherwise slippy) day.

The S1 tunnel can be accessed by land. See entry for S entrance. Best in bottom half of tide. The whole S1 tunnel can be viewed from the S1 chamber.

A visit into the S entrance on 15 May 24 discovered that about 1m or more depth of shingle had been removed by wave action and that the N part of the rift tunnel to the S entrance had become much larger in cross section as a result. It seems possible/probable that the S entrance is also a blowhole. The next high wave/swell storm will allow this to be confirmed - or not.

Links and Resources:

Personal communication from Nigel Feilden, 11/9/2018. Survey trips 19/3/20, 8,22,25/7/20, 15/5/24 NF.
This cave system is not marked on any OS map up to 7/20. But it has been known locally for a long time as evidenced by this extract from "The Caves and Birds of Fowlsheugh" by James Reid, pp 82-85 in the 3rd Deeside Field of 1927: "Between the Kaim and the Ba' a great cave has been hollowed out. In storms great seas rush in and completely fill it, and the compression, with loud snoring noise, sends the spray high into the air through holes that pierce the roof. With caution one may sail into this gloomy tunnel for 30 yards and then abruptly turn [right] into complete darkness. By crumpling up a number of newspapers, setting light to them and allowing them to float on the surface, it is possible by the aid of these blazing torches to proceed with great caution a few yards further." The Kaim is Maiden Kaim while the Ba' is marked Strabandra Knap on the OS maps. See p40 below for the full text of the article.
www.youtube.com/watch?v=WhZdEdtDS1A shows the bottom 3 blowholes operating with about 2.5 m NE swell - according to windy.com See elevation p30 and photos p31 onwards for more info on the blowholes.
p1) www.geograph.org.uk/photo/6350390 shows the entrance to the main tunnel on a calm day, with the blowholes above the line of that tunnel. Strabandra Knap is on the left.
p2) www.geograph.org.uk/photo/6627637 is a nice blow from blowhole #2
p3) registry.gsg.org.uk/files/2788/StrabKnapBholeCave_plan29jul20.jpg is a sketch plan which is accurate for length and the direction of the tunnels, less so for widths and fine detail.
p4) registry.gsg.org.uk/files/2788/StrabKnapBholeCave_plan29jul20_picsA.jpg is the same plan with the last 3 digits of the below photos marked in red.
p5) registry.gsg.org.uk/files/2788/DSCN0665r.jpg shows the entrance from closer than p1) above.
p6) registry.gsg.org.uk/files/2788/DSCN0189r.jpg was taken from just under the entrance opening, looking out. The curved overhang on the left suggests that the main tunnel was once considerably longer.
p7) registry.gsg.org.uk/files/2788/P9011225r.jpg was the view seaward standing on top of the entrance arch on 1 Sep 20, with a fairly high tide level.
p8) registry.gsg.org.uk/files/2788/P3060156rlbl.jpg taken from about 4m inside the main tunnel, looking W by S at the first and second arches. The bottom entrances to the #1 and #2 blowholes are directly overhead.
p9) registry.gsg.org.uk/files/2788/P3060159rlbl.jpg see p4 for camera location; looking WSW at the second arch in the main tunnel, after which S1 tunnel goes off to the left and the N chamber opens to the right.
p10) registry.gsg.org.uk/files/2788/P3060162rlbl.jpg see p4 for camera location. Shows the junction of the main tunnel and S1 tunnel from the SE corner of the N chamber.
p11) registry.gsg.org.uk/files/2788/P7220880rlbl.jpg see p4 for camera location. The entry to tunnels S2 and S3. On p4, the dotted curve indicates an overhang which, like the tunnel entrances, is submerged at HW. S2 (on left) is reported (see Notes) to be kayak navigable when the tide level is quite a bit lower.
p12) registry.gsg.org.uk/files/2788/P7220885rlbl.jpg see p4 for camera location. Taken from towards the SSW end of S3, just before the S2+S3 chamber. The dividing wall/pillar between the S2 and S3 extensions can just be made out, a little to the right of the kayak's bow.
p13) registry.gsg.org.uk/files/2788/P7220888rlbl.jpg see p4 for camera location. Shows the S2 extension - complete with orange & blue buoy jammed in the end. Iain Greig has found this the rule rather than the exception in the Arbroath seacaves as well.
p14) registry.gsg.org.uk/files/2788/P7220887rlbl.jpg see p4 for camera location. Shows the S3 extension. Not a great photo - but the rift extends 14.2 m (laser) and some way upwards. By eye it looked as if the bottom of the Tremuda basalt layer might be visible.
p15) registry.gsg.org.uk/files/2788/P7220889ralbl.jpg see p4 for camera location. The SSW end of S2 from the S2+S3 chamber. It is reported to be kayak navigable when the tide level is lower (see notes).
p16) registry.gsg.org.uk/files/2788/P7220895r.jpg see p4 for camera location. Looking about S from near the middle of the N chamber. Shows the roughly horizontal ceiling in this chamber and also how the rifts leading to S1 on the left, and S2&S3 on the right, splay outwards as they go up on both sides. This, presumably, is what holds the ceiling up - so far. An unresolved issue is how thick the ceiling above the camera location is. There is a relative flat, wavecut platform area above. A very rough estimate (1/9/20) suggests it might be as little as 2m - but it really needs a proper survey above.
p17) registry.gsg.org.uk/files/2788/P7220894rlbl.jpg see p4 for camera location. Looking N from a bit S of the middle of the N chamber. It narrows down, and then the N extension tunnel runs over 20m from the NW corner. Some flowstone has formed around the ceiling/wall joint or the right (E) side - but nowhere near as much as in the caves under Fowlsheugh to the south - which is a completely different conglomerate formation. The photo happened to capture the eye and muzzle reflections from two seals nearby, under water.
p18) registry.gsg.org.uk/files/2788/P7220896rlbl.jpg see p4 for camera location. The entrance to the N tunnel extension. It looks a bit short of headroom in this photo, but was reasonably comfortable on the day.
p19) registry.gsg.org.uk/files/2788/P7220897r.jpg Inside the N tunnel. The rift has gone from a noticeable lean to the left (W) in p16, to vertical.
p20) registry.gsg.org.uk/files/2788/P7220898rlbl.jpg see p4 for camera location. The beach at the N end of the N extension tunnel. The laser found an end 8m beyond the beach. Note that the rift now leans a bit to the right (E).
The following images are of or about the three blowholes:
p30) registry.gsg.org.uk/files/2788/Elevation_r1a.jpg is a sketch elevation of the main tunnel, as from the N side, showing (rather roughly), the three blowholes and the transverse tube #2-3 from near #2 up and across to join #3. How close this is to the top of #3 has not been determined yet.
p31) registry.gsg.org.uk/files/2788/P9011228rmu.jpg was taken from the rocks on the NE side of the main entrance. It shows the main entrance with a fairly high tide level, and the top exits of bottom two blowholes marked, with lines to show roughly the angles at which they blow out. See p2 above for a blow from #2.
p32) registry.gsg.org.uk/files/2788/P9011226rmu.jpg was taken from the same place as p31, and has the locations of the top exits of the three blowholes marked.
p33) registry.gsg.org.uk/files/2788/P9011223r.jpg is a closeup of the top exit from #1. The top is somewhat rectangular, a bit like some fuel funnels, and is 2.00m long on the 080 axis and 1.12m wide at the top. From the bottom, it looks lemon shaped - see p34
p34) registry.gsg.org.uk/files/2788/D8220469r.jpg was taken of the bottom entrance to #1 on 22 Aug 19, from where it looks rather like a lemon profile, with the ends of the lemon in line with the 080 axis of the main tunnel.
p35) registry.gsg.org.uk/files/2788/P3060153r.jpg was taken on 3 Mar 20 and shows how close the bottom entrances to #1 (the upper one) and #2 are. It was taken looking up and with the photographer's back to the entrance of the cave's main tunnel. Those blowhole entrances are also in a small aven compared to the rest of the main tunnel. Now look at p2 and wonder how #2 could blow like that with very little coming from #1! To be fair, there is some mist going up from #1 and there is a breaking wave somewhat covering it.
p36) registry.gsg.org.uk/files/2788/P9011238r.jpg is back on top, 1 Sep 20, standing as high as could be to take p38, and looking down at the top exit of #2, and below it, what can be seen from there of #1, and the sea beyond the main tunnel entrance. Note the way #2 is also somewhat rectangular, but significantly twisted away from the 080 axis. The black crust on the conglomerate is black tar lichen (verrucaria maura).
p37) registry.gsg.org.uk/files/2788/P9011233r.jpg is a closeup of the top exit from blowhole #2, taken from the S side. You can see the sea in the main cave tunnel below. It is 0.46 m x 0.38 m at the top. The red crust is thought to be Hildenbrandiae Rubra, a red alga common in seacaves, out of direct sunlight. The angle of the tube looks close to vertical, although when it blows, its spout usually leans a bit west of vertical - but when it blows, the wind is usually from the E ...
p38) registry.gsg.org.uk/files/2788/P9011237r.jpg is the closest view of the top exit of blowhole #3 so far available. A better photo will probably require a rope from above, or a ladder from below.
p39) registry.gsg.org.uk/files/2788/DSCN0469r.jpg is a view of the bottom entrance of blowhole #3, taken 13 Sep 18, looking E by N. This is about 10-15m WSW of the bottom entrances of #1 and #2, and between the first and second arches visible in p8. The brownish areas are thought to be flowstones. This blowhole tube is quite narrow at the bottom - but is yet to be measured top or bottom. It spouts at approximately 45 degrees. It has often been seen to spout or puff mist, significantly out of time from the other blowholes.
p40) Full text of 'The Caves and Birds of Fowlsheugh' by James Reid in The Deeside Field, vol 3, 1927, pp82-85 with added footnotes.

This entry was last updated: 2024-12-12 14:54:31

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NGR:	NO 88115 83323
WGS84:	56.94102, -2.19696
Length:	254 m
Vert. Range:	18 m
Altitude:	-6 m
Geology:	Dunnottar Conglomerate
Tags:	Cave, SeaCave
Registry:	main

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