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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