Natural Bridge, Mount Eccles

The cave is located towards the end of a small lava channel that runs from a subsidiary crater to the Southeast of Mount Eccles.

Note that although you can explore much of the cave by natural light from the entrances, you should bring torches (with decent batteries!) if you want to go right through as it gets a bit gloomy in the middle and it is easy to slip on the damp rock. A bright floodlight will show the full range of colours, which is not normally visible

The origin of the Cave.

Natural Bridge is a "lava tube" formed by the roofing of a lava channel. The diagram shows a long section and cross-sections. The sections show the angular "gothic" roof shape which indicates that this roof developed by the inward growth of levee banks on each side. This process is described in another page. As well as growing out and over the channel to form a roof the layered banks slumped downward while still semi-liquid. We can see the resulting contorted layers exposed within the cave where parts of the lining have broken away.


Entrance to Natural Bridge Cave, Note "gothic" roof shape.	Contorted roof inside the cave indicates slumping of the levee layers.

Features of the cave.

If you have a bright light you will see colour variations on the walls - the green is mosses and lichen growing in the low light from the entrances, and the various rich shades of cream, brown and orange which are the natural colours of the basalt rock and minerals weathering from it.

The small hole on the surface connects to the main cave below. Do not climb into this. The guard rail is there for a good reason - the apparent floor of the small upper chamber often has a cover of loose leaves which can hide a dangerous hole and 10m fall into the main cave below!

Surface features

To the north of the bridge you can see the lava channel which was roofed to form the cave. The narrow section next to the cave may also have been roofed, but it has since collapsed. To the south the channel widens and looses its character rapidly. The lava river must have spread out at that point to form a broad "delta".

There is an interesting walk from the car park, back up the lava channel to its source in a small crater, and you can continue from there right back to the main crater and lake at Mount Eccles.

[Top] [Home]

Last modified on 2 Sept 1998
HTML: Copyright © 1998 K.G. Grimes Email: ken-grimes@h140.aone.net.au
May be reproduced for non-commercial use provided this copyright notice is retained in full.
URL for this page:http://www.netserv.net.au/cwork/ackma99/grimes/VC3H10.htm