Sydney Harbour (Port Jackson) EarthCache EarthCache
Sydney Harbour (Port Jackson) EarthCache
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This EarthCache is located at Shark Beach on the edge of Sydney Harbour, also known as Port Jackson. The aim of this EarthCache is to learn about the geological make up of Sydney Harbour.
To complete this EarthCache you will be required to visit 2 locations that are fairly close walking distance to each other. Although the EarthCache can be completed at anytime, I would suggest visiting during low tide so more of the geology is exposed. As you will be close to Sydney Harbour please take care when visiting both locations. If there are large waves or a heavy swell you may want to try again another day. There is no need to walk along thr rocks or through the water to reach the second location. A path is located some of the way from Shark Beach to Vaucluse Point
Sydney Harbour is made up of mostly sandstone and shale formed during the Triassic period (about 220 million years ago). These formations were later raised to their present heights by earth movements, starting in the Jurassic period, (200 million years ago). At that time, Australia was part of the Gondwana supercontinent, and the Sydney region was a large freshwater lake. This was slowly filled up by deposits of sand, mud, silt and pebbles, washed in by large rivers. Over the millions of years that followed, these sediments were gradually overlain by others. They were compressed into sandstone, mudstone and shale.
During this time great cracks formed and molten lava rose up through the rocks to form volcanic vents, these then cooled and hardened to form dykes of basalt. Remains of basalt dykes can still be found around Bradleys Head, North Head and Nielsen Park.
Two to 12 million years ago, the Sydney plateau was uplifted by movements in the earth's crust. The Parramatta River and its tributaries flowed across this plateau, gradually cutting deep V-shaped valleys into it and leaving narrow sandstone ridges behind. About 6000 years ago, when the sea rose to its present level, the Parramatta River valley was drowned - and Sydney Harbour came into being.
The eastern part of the harbour is predominantly Hawkesbury sandstone. Sandstone is a very hard rock that tends to break away in large blocks leaving the boulders and vertical cliffs that characterises the Sydney coastline.
To the west the harbour is predominantly made up of Ashfield Shale. Shale is not as hard as sandstone and tends to weather and erode without forming boulders or cliffs. As a consequence the western shoreline of Sydney Harbour tends to be much flatter and devoid of rocky outcrops.
Along some parts of the harbour there are some low lying areas of sand that has been deposited by water (alluvium) running between hills of sandstone. Particularly high areas such as North Head and South Head which were once islands are now joined to the mainland by sand spits such as the Corso area of Manly and the low sandy area between Bondi and Rose Bay. Smaller amounts of sandy material have been deposited by streams where they enter bays on the southern side of the harbour, such as Rushcutters Bay, Darling Harbour and Homebush Bay.
You MUST attend the EarthCache locations and message me answers to all of the questions and uploaded the required photos to claim a find. Any logs without ALL of these will be deleted, no exceptions!!
There is no need to wait for a confirmation message to log this earthcache. I read all messages to verify the correct information was sent and will contact you if there are any problems with your answers. Likewise, there is no need to email me photos. Just upload any photos with your log. If both tasks are not completed within a timely manner of logging your cache online your log will be deleted.
Please take care while attempting this EarthCache.
Disclaimer: Always exercise common sense and caution. You assume all risks arising in connection with seeking this EarthCache or any other related activity. If the rocks are slippery, waves too high or you feel in danger in anyway please do not attempt this EarthCache..
Location 1
Make your way to the EarthCache location and perform the following tasks:
1) Upload a photo of you or your group clearly showing your GPS, Sydney Harbour and some of the geology in the background at the EarthCache location.
Email me answers to the following questions :
2) As close as you can to the EarthCache location ( and taking all safety precautions) walk to the water’s edge and describe the geological make up of the floor of Sydney Harbour at this location. Is it made up of sand, shale, coral, sandstone, pebbles or mud? A combination of these?
3) Given the EarthCache information above; how did this most likely get here?
Location 2
Make your way to Vaucluse Point (Waypoint 1 - S33° 50.868 E151° 16.196 ) and perform the following tasks.
4) Upload a photo of you or your group clearly showing your GPS, Sydney Harbour and the rock outcrop at Vaucluse Point location.
Email me answers to the following questions:
5) Run your hand across the rock surface.
a. Describe the type of rock that’s located here?
b. The colour, texture and smoothness of the rock.
Additional Hints
(No hints available.)
Treasures
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