Gunns Plains Cave

..... Limestone Cave

I haven't posted much of late. That's partly due to being busy and partly due to having broken my SLR camera. It seems the repair bill may be $300 or more so I taking my time deciding whether to repair or upgrade. In any case it meant that on a recent visit to Gunns Plains Cave I had to make do with a small compact camera. The images are not great but they at least give an idea of some of the magnificent formations within the cave. Some better quality shots can be seen in an older post here.

The public access to the cave takes you a little short of 300 metres in and to a depth of around 55 metres. Speleogists have mapped the cave to at least another 1 km.

In no particular order, here are the cave photos:

(Click on photos to enlarge)

#1

#2

#3


#4 - Helectite

#5

#6

#7 - This shawl formation is reputed to be the largest in Australia

#8

#9

#10 - This stalactite looks like a giant uvula

#11 - The wedding cake. The dark areas are caused by bushfire smoke (possibly centuries ago) entering the cave.

#1 2 - The creek that flows through the cave.
Home to the Giant Tasmanian Crayfish which grows up to a metre in length.

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Gunns Plains Cave

Gunns Plains Cave is located 20km south of Ulverstone. This limestone cave was discovered in 1906 by Bill Woodhouse while on a hunting trip. There seems to be two versions of the story. One that a possum eluded him by going down a hole into the cave and another where his dogs fell into the cave. Of course it's not hard to imagine that both are true if the dogs were chasing the possum. Since that time tourists have come from far and wide to witness the spectacular limestone formations. The area was declared a state reserve in 1918 and access was improved early on by making a new entrance through the side of the hill and building a concrete stair case which is still in use.

The cave has been cut by an underground river which still flows through it today. There are a good variety of cave formations (speleothems) including what is claimed to be the the largest shawl formation in the world.

When I was last there one cave spider was pointed out to me although it was in a crevice so it wasn't easy to see and was impossible to photograph. Easier to see were the threads from Glow Worms, Arachnocampa tasmaniensis, hanging from above. Other wildlife that has been seen within the cave includes the platypus and the Tasmanian Giant Freshwater Crayfish, Astacopsis gouldi (the worlds largest freshwater invertebrate).

(Click on Photos to Enlarge)

Gunns Plains Cave - The Golden Fleece

Gunns Plains Cave

Gunns Plains Cave

Gunns Plains Cave - Shawl Formation - Claimed to be the largest in the world.

Gunns Plains Cave - note the stairway for scale

Arachnocampa tasmaniensis - Glow Worms at Gunns Plains Cave

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Tasman National Park - 2

In addition to the geological features in yesterdays post, the Tasman National Park also has the Tessellated Pavement

Tessellated Pavement

This siltstone rock platform has the appearance of being tessellated or tiled. Geological stresses have caused the jointing (cracks) in the siltstone. A combination or chemical and physical processes have then eroded the surface and creating the tiled appearance. The physical erosion (wave erosion) caused by water and rock fragments washing over the platform has a greater effect on the joints. The chemical erosion (salt wedging) has a greater effect on the surface between the joints. This is caused by salt crystallising between the rock grains. As the salt crystals grow between the rock grains, they cause the rock surface to flake away.

The above processes, if I have described them clearly, will explain the two main features on the rock platform, namely loaves and pans.

The area nearest the sea is under water longer and thus experiences more physical erosion. This eats away at the joints leaving a loaf formation.

Loaves

The area furthest from the sea is left high and dry for longer thus aloowing for greater development of salt crystals and less physical erosion from the sea. This eats away at the sutface of the rock and the joints are left like little ridges, thus forming a pan shape.

Pans

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Tasman National Park -1

On Friday I had the opportunity to visit the Tasman Peninsula and the Tasman National Park. Here is a glimpse of some of the areas spectacular coastal scenery and geological features.

#1 - Looking south along the sea cliffs near Tasman Arch

The Blowhole
Here, wave erosion has formed a tunnel through a weak point in the rock. The waves also compress the air at the end of the tunnel. Eventually these processes have extended the tunnel until it formed a hole at the far end.

While photographing the blowhole I also noticed a couple of Superb fairywrens flitting about some washed up kelp. I assumed they were after flies and other insects which had been attracted to this rotting seaweed. The Fairywrens were also, now and then flying into the entrance of the blowhole tunnel right in amongst the surf spray. If you look at the photo, they were flying to a point at the upper left corner of the tunnel entrance and maybe several feet in. I have no idea what they were doing in there.

#2 - The Blowhole

Tasman Arch
This has been formed in much the same way as the blowhole only it has been a large sea cave as opposed to a smaller tunnel. Eventually the roof of the cave at the landward end has collapsed leaving a natural and rather spectacular arch.

In the photo below, the safety fence on the far side gives a bit of scale. A short walk from here there is a lookout where photo #1 was taken.

#3 - The Tasman Arch

Devils Kitchen
The Devil's Kitchen is very close the the Tasman Arch. This also would have been a cave but the entire roof has been lost. Cracks in the rock have have caused the weak point for this erosional process and this is also the reason for the vertical sides to this formation.

#4 - The Devil's Kitchen

Remarkable Cave
Here I shall quote verbatim from a National Parks pamphlet which says:

Remarkable Cave is a striking example of dolerite contact with sediments folded in the cave roof. It has formed as the result of the intersection of two large sea caves, eroded along two zones of weakness over many thousands of years. It is called ‘remarkable’ because some say the opening resembles the map of
Tasmania.

#5 - Remarkable Cave

#6 - Coastal Scenery near Remarkable Cave

#7 - Coastal Scenery near Remarkable Cave

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