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61105.  Tue Mar 21, 2006 4:58 am Reply with quote

Question: Which Australian landmark is the world’s largest monolith?

Forfeit: Uluru, Ayres Rock.

Answer: Mount Augustus.

The word monolith, from the Greek for single rock, describes a natural feature consisting of a single huge stone or rock. Many people believe that Ayres rock is the largest of this particular geological feature in the world, but they’d be wrong, on two counts,

Firstly Uluru is not a monolith, it is not an isolated rock, rather it is part of a giant underground rock formation, of which only a couple of parts are above ground. But that’s not the only problem, you see even if Uluru was counted as a monolith it wouldn’t be the largest, not even in Australia, and not by a long shot. The actual largest monolith is called Mount Augusta, or Burringurrah. It is found in Western Australia, and is over 2.5 times the size of Uluru.

Last edited by eggshaped on Tue Mar 21, 2006 5:24 am; edited 1 time in total

61111.  Tue Mar 21, 2006 5:22 am Reply with quote

It's supposed to resemble a boy lying on his side with a spear sticking out of his thigh:

We might want to tie down why Ayers Rock isn't regarded as a monolith (as backup info, not because the question depends on it).

The Rock of Gibraltar is a monolith, as are three big rocks in the UK: Humber Stone near Leicester, and King Arthur's Stone and Logan Stone in Cornwall.

61117.  Tue Mar 21, 2006 5:33 am Reply with quote

Here's the reason I had: the way I took it was that there is a small mountain range in the Uluru area which has mostley been covered by sediment.

According to Sweet and Crick (1992, Uluru & Kata Tjuta: A Geological History), about 550 million years ago erosion from the Petermann Ranges led to huge alluvial fans (at least 2.5 km in vertical thickness) being built up by deposits of Arkose sands from the eroded materials of the adjacent ranges.

Fifty million years later these alluvial fans were covered by sediments when the region became a shallow sea (isostatic subsidence due to the loading caused by these Arkose sand deposits playing a role in this process).

Then during the period from c. 400 to c. 300 million years BC, another uplift (the Alice Springs Orogeny, which created the Macdonnell Ranges to the north of the Uluru area) caused massive folding and faulting in the region, causing the formerly horizontal strata of the Arkose sandstones which comprise Uluru to be folded nearly vertically from their former position (i.e., rotated vertically nearly 90 degrees from their original bedding planes).

Then subsequent erosion over the past 300 million years has led to the uncovering of the Arkose sandstones which comprise Uluru and its gradual shaping by erosion into the huge 'monolith' which we can see there today.

The deposits which previously covered the Arkose sandstones have largely been eroded away, so that 'The Rock' stands high over the surrounding desert plain because its rock is more resistant to erosion than were the rocks which formerly covered it.

Massive link which annoyingly has the above quote in white font which needs highlighting:

70947.  Mon May 22, 2006 3:42 am Reply with quote

Underwater Uluru found off the coast of Western Australia:

Oceanographers have discovered an underwater structure, the size and dimension of Uluru, off the coast of Augusta, in Western Australia's south-west.

The feature, which has been named Mt Gabi, lies one kilometre underwater and is 300 metres high and about five kilometres long.

Don't know if this made the news in the UK, but its probably worth knowing about.


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