SAWMILL SINK, ABACO: INDUSTRIAL ARCHAEOLOGY IN A POST-APOCALYPTIC LANDSCAPE


Sawmill Sink (adventureactivist youtube)

SAWMILL SINK, ABACO: INDUSTRIAL ARCHAEOLOGY IN A POST-APOCALYPTIC LANDSCAPE

1. BLUE HOLES

The Blue Holes of Abaco are geological wonders about which much has been written – much of it in the NATIONAL GEOGRAPHIC MAGAZINE. Sawmill Sink is one of the best-known inland ones; and there are other holes in the shallow seas on both sides of the island. They are deep chasms in the limestone rock, many leading to extensive and complex cave systems under the island. Divers exploring Sawmill Sink have found many prehistoric fossils, including those of an extinct giant tortoise, and land crocodiles. Most conveniently, this fascinating blue hole is close to Delphi, hidden deep in the pine forest and accessible only by historic logging tracks.

LOGGING TRACK TO SAWMILL SINKSawmill Sink Abaco 19

AERIAL VIEW OF SAWMILL SINK DEEP IN THE PINE FORESTSawmill Sink Map copy

This article is not about Blues Holes in general, nor Sawmill Sink  specifically. I have such a post planned, but for the moment I’ll put some relevant links at the end of this one. Feel free to scroll straight there if the cumbersome heading has already put you off… but in an effort to hold your interest, here’s an image of the Sink to give you an idea of what it looks like. There are wooden steps down and a platform to enable you to swim in it (there are no crocodiles these days. So they say…).

SAWMILL SINK, ABACOSawmill Sink Abaco 8

2. A LOGGING HISTORY

South Abaco – defined loosely as the area south of Marsh Harbour – is dominated by pine forest. There are a few settlements and individual residences, all by the coast. The forested swathes are criss-crossed by an extensive system of logging tracks, many now all but impassable. They are reminders of Abaco’s historic importance as a source of wood deriving from the ubiquitous tall, slim pines. One use to which they were put was as mine pit props in the collieries of Wales.

 1996.2039.db

Last June when we went to Sawmill Sink, we saw a rusty rail sticking up from the undergrowth. We were with Ricky Johnson, the man who could invariably answer any question about Abaco; he explained that there had at one time been a light railway through the forest to carry the felled timber to the highway, where it was transported to the coast for loading onto ships.Sawmill Sink Abaco 17

Last month we returned to Sawmill Sink. The south part of the island was enduring the annual outbreak of forest fires, most (if not all) believed to be set by hunters wanting to clear to undergrowth to make hog-hunting easier. While the occasional natural fire is actually good for the forest (cf burning moorland), the set fires do great damage over a vast area. On some days there were 6 or more separate seats of fire appearing in one day – highly unlikely to be the work of nature. Thick palls of smoke drifted across the island, and out to sea. Even far out on the Marls, the fires were visible, with the smell of burning carried on the wind. This year, the fires came uncomfortably close to some of the settlements. Night-long community action was needed in some places to protect property. At Delphi, the fires came within 300 feet or so before finally fizzling out in the coppice… Two years ago, they  came nearly as close. For a post-fire wander round the Delphi drive circuit click FOREST FIRES (it was one of the first, tentative posts on this blog – and boy, does it show… it needs a rethink)

DELPHI GUEST DRIVE: A WARM WELCOMEForest Fire, Delphi, Abaco

The photos that follow show the track to Sawmill Sink immediately after a fire had swept through the area. Trees were still smouldering and in places the ground was still hot to the touch. Along the way the evidence of the former usage had been laid bare. Some images show the paved path that leads from the logging track to the Sink. I have no idea if these are the first images of so many visible remains of the logging trade, revealed by the burnt-off undergrowth. I haven’t tracked down any others at all so far. I write as a non-resident of the island, so if anyone can add any information, please do so via the COMMENT box. Sawmill Sink Abaco 1 Sawmill Sink Abaco 2 Sawmill Sink Abaco 3 Sawmill Sink Abaco 5 Sawmill Sink Abaco 6 Sawmill Sink Abaco 7 Sawmill Sink Abaco 9 Sawmill Sink Abaco 10 Sawmill Sink Abaco 11 Sawmill Sink Abaco 12 Sawmill Sink Abaco 13 Sawmill Sink Abaco 14

Finally, we found this rock close to the Sink. Are those plant fossils? Bearing in mind that sea probably covered this area entirely (the highest point on Abaco is a mere 134 feet ASL), might these be anemones or sponge fossils of some sort? Comments from fossilologists welcome.

STOP PRESS thanks to FOSSIL LADY (aka Kathi) for the following: “Those don’t look like plant fossils to me, they remind me of stromatolites, a sponge like creature that first dominated the earth billions of years ago. Some varieties still survive today. It would be worth it to have a geologist have a look see. ps the sinkhole is awesome!”Sawmill Sink Abaco 15

SOME BLUE HOLE LINKS TO EXPLORE 

BAHAMAS CAVES RESEARCH FOUNDATION

FRIENDS OF THE ENVIRONMENT, ABACO

NATIONAL GEOGRAPHIC

ADVANCED DIVER MAGAZINE ARTICLE

As a reward for having waded through the smoke and ash above, here’s a short video of what you can see if you dive in a blue hole. It’s worth saying (1) that you need to check you are allowed dive – some holes are subject to ongoing research and (2) blue hole diving and caving is an inherently unsafe activity unless you have the right equipment and know exactly (by which I don’t mean “hey, I can wing it”) what you are doing… 

[vimeo http://vimeo.com/37838009]

Photo credits: all RH except header (adventureactivist, youTube); pit props (Scottish Mining Museum); aerial view (Gmaps)

“ROCK & ROLLING WAVES”: ROCK EROSION ON ABACO


Rock Erosion Gilpin Point 3

“ROCK & ROLLING WAVES”: ROCK EROSION ON ABACO

On 26th October 2012, the ‘roof’ of the geological feature at the southern tip of Abaco known for centuries as Hole-in-the-Wall was blasted apart by Hurricane Sandy. The combination of huge waves and powerful winds proved too much for a structure that had existed since the last ice age. I posted in detail about this event last year HERE so now I will concentrate on some geological aspects.

The photo below shows the Hole a year or so before its destruction. At the left-hand end of the bridge there is a paler area underneath where limestone rock had recently fallen into the sea, suggesting an underlying instability. At close quarters there were plenty of cracks in the apparently solid structure. (I’ve no idea why I didn’t straighten the image. Let’s say… Artistic Perspective)hole-in-the-wall-abaco-ricky-johnson

This photo was taken a few days after the collapse, the first to be published of the new view. The clean white rock at either end of the ex-bridge is clearly visible. The section on the left became a new islet at the southern extremity Abaco, separated from the mainland for the first time in history. I proposed various names for it (not all serious) – Sandy Cay (or Isle) was the clear, indeed obvious, winner…

Hole-in-the-Wall Abaco- the new gap Nov 2012

This close-up of the south side of the bridge shows the detail of the rock fragmentation. Tara’s photographs are (as far as I know) the very first of the new gap and of Abaco’s new islet, predating John Haestad’s by a day.HOLE-IN-THE-WALL ABACO post Sandy 3

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We recently went to a beach near Crossing Rocks that we had never explored before (plenty of interest there for later posts). We were struck by the fragmented and pitted nature of the limestone rocks on the shoreline. We noticed some pale exposed rock surfaces, similar to those at Hole-in-the-Wall. We watched the incoming waves scouring and undercutting the rocks, leaving overhangs (see video below). Erosion is increased by the double action of the waves. The immediate area hinted that there may even have been a very small Hole at one time. On the day we were there, the sea was gentle. It’s easy to imagine how the hugely destructive force of the wind and crashing waves resulting from hurricanes such as Sandy can eventually shatter solid rock that has been gradually eroded and destabilised over centuries by wave action.Rock Erosion Gilpin Point 1 copyRock Erosion Gilpin Point 2 copy

Photo credits as shown / RH. You have Mrs RH to thank for a shorter (50 secs) video than the one I originally made (75 secs). Now I’ve redone the thing, I agree – one wave does look very like the next… 

ADDENDUM Just remembered that I took an aerial photo of HitW from the plane the other day. It’s a phone photo through BahamasAir window glass, and I’ve had to tweak it a bit. It shows the relevant area…all the blurry dark stuff is part the pine forest of the National Park 

Image - Version 2

ADDENDUM 2 In response to a comment about the power of hurricanes, here is an image I have posted previously of a large rock some way out from the Delphi beach. Before Hurricane Irene in 2011, it was a solid rectangular slab. This is what it was like after Irene had moved on northwards  Delphi Blasted Rock