Hummock Hill was the site of first settlement at the turn of the century, and during World War II it saw service as a gun battery with four guns and command and signals posts - in fact development of the lookout utilised the old gun emplacements which can still be seen today.
Early stages of the fortifications were built by BHP workmen, but the majority of the work was carried out by gunners of the 26th Heavy Anti-Aircraft Battery under the supervision of the 65th Deputy Commander Royal Engineers who arrived in Whyalla on February 14, 1942. When the battery reached full strength there were approximately 120 men under the command of Captain R L Moorfoot.
Hummock Hill affords an unequalled view of Whyalla and the vast OneSteel operations; Whyalla Foreshore and Marina; across Spencer Gulf to the Southern Flinders Ranges and including the nearby Santos plant at Port Bonython and the Point Lowly Lighthouse; and westward over the city towards the iron ore rich Middleback Ranges.
The geology of Hummock Hill is unlike the rest of the surrounding area of Whyalla. It has a totally different geological composition to both Mt Young to the south and Mt Laura to the north west. They are primarily of the Moonabie Formation – consisting of volcaniclastic grit and sandstones. Hummock Hill is of the Corunna Conglomerates and consists of an off-white to purple boulder and pebble conglomerate along with minor sandstones. It would also be classified as being extraformational in that it is composed of clasts that are derived from older formations than the formation in which it finds itself. [Clastic rocks are composed of fragments, or clasts, of pre-existing rock. Geologists use the term clastic with reference to sedimentary rocks as well as to particles in sediment transport whether in suspension or as bed load, and in sediment deposits.]
Over the years the sea has had a considerable effect on Hummock Hill. In a few millions years from now the chances are that the hill will have disappeared completely.
Standing at the indicated co-ordinates you need orientate yourself on the beach with your back to the sea and looking towards Hummock Hill. In front of you will be a series of erosional features just beyond the fenced off area. The composition of the conglomerate is clearly visible. You need to have a careful look at what you see and then answer the questions below in order to be able to claim this EarthCache. Submit your answers, by e-mail, to cincolcc(at)gmail.com
1. What do you think caused the formation of Hummock Hill as you see it today?
2. In front of you are a number of caves. Estimate the width and depth of the largest cave that you can see.
3. Look at the larger smooth, round “stones” that you see embedded in the conglomerate. Would you say they are bigger or smaller than a baseball?
4. Looking north from GZ – towards the One Steel complex – there is an object on the beach. What is this object? [This will ensure that no armchair loggers attempt to log this EarthCache.]
Some anecdotes from a local cacher - YeahRight80 - reproduced with his permission.
"Twenty years ago these caves stretched right around the hill back toward the boat ramp, some were huge..... big enough to park many cars underneath, tunnels stretched up between and around the area and as a kid I played there hundreds of times. BHP eventually got worried about the liability and dynamited them. Only then did the Aboriginal people from this area complain terribly, claiming the area was a long time summer camp. The bar of stones that runs seaward marking the path of the old original ore loading jetty which was accidentally burned down in the late 1970's by two kids who were fishing out the end and left their fire burning. [ I know the history of the jetty because the old ore jetty was burned down by two of my then friends Alan Brown and Brendan Blackburn.]"
References consulted.
Whyalla Geological Survey of South Australia - Department of Mines and Energy, Adelaide
http://www.geoscience.gov.au/bin/250dpi?img=250dpi/si5308.jpg
http://www.whyalla.com/site/page.cfm?u=133
FTF goes to = Bunya - Well Done!!
