The Nullabor Plain is the world's largest single exposure of limestone bedrock, and occupies an area of about 200,000 square kilometres (77,000 sq mi). At its widest point, it stretches about 1,100 kilometres (684 mi) from east to west across the border between South Australia and Western Australia.
The Nullarbor Plain is a former shallow seabed, as indicated by the presence of various calcareous skeletal material that make up the limestone. The region is also the location of "Nullarbor limestone" and it has a reputation as a significant karst region with Oligocene and Miocene cave formations.
The cliffs of the Great Australian Bight mark a dramatic boundary between the vast expanse of the Nullabor Plain and the cool blue waters of the Southern Ocean. The cliffs are high, formed millions of years ago when the seabed was pushed upward and exposed the limestone underneath. These cliffs stretch for hundreds of kilometres and have varying coloured hues observed from the ocean side.
The sea pounds the cliffs relentlessly with huge waves and powerful southerly winds, but the rock strata are horizontal and vertical joints are very regular, with no weaker sections for the sea to gouge out caves or valleys. The result is that the cliffs erode by being undercut, whole slabs falling off at a time, leaving a very straight coastline, the plateau continuing to drop vertically to the sea. Behind the Israelite and Roe plains the cliffs are some distance inland from the sea, but remain vertical, having been eroded by being undercut in times of higher sea level.
To verify your find of this cache you need to answer the following questions.
1. What are the 2 predominant colours observed in the cliffs at this cache location?
2. What do you think caused these different colours?
3. Where you are standing is part of an eroded sea bed which forms the cliffs. What is the approximate elevation above sea level of the cliffs found at this cache?
Send your answers to me via Geocache email messaging. You can log your find straight away, but please understand logs will be removed if no email is received or answers incorrect/guessed.
If you are crossing the Nullabor, perhaps visit my other earth Cache "Under the Nullabor" found here: http://coord.info/GC5BZ1E
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