Welcome to Lake Macquarie. There is no need to get wet at GZ as all the information can be found on land however you might like to go for a sail afterwards or enjoy the nearby hospitality. Access to GZ is through The Club (Belmont 16's) who have kindly given their permission to access GZ. They (The Club) have asked members obey their membership rules and that non members sign in and obey the rules. There are also dress rules for all to comply with.
Lake Macquarie is the largest coastal salt water lake not only in Australia but also the Southern Hemisphere at over twice the size of Sydney Harbour. It has a surface area of approximately 110 sq km and length of 24km and width of 3.2km.
In geological terms Lake Macquarie is still quite young, formed only 6,000 years ago. Many parts of low lying suburbs such as Dora Creek, Blackalls Park, Speers Point and Teralba, located nearby to creek systems were actually part of the Lake only a few thousand years ago. The lake contains 12 major, and many more minor, estuarine creek zones where freshwater tributaries interface with the saline body of the main lake.
The formation of Lake Macquarie, as it is a geomorphic feature rather than a geological feature, though its formation is due to a combination of natural physical processes. The lake is essentially just a drowned embayment, its origin is possibly older than just the last sea level rise at the end of the recent Ice Age. The erosion of the conglomerates and sandstones (of Middle Permian age, roughly 200 million years ago, that largely form the shores of the lake), by the numerous but only small creeks draining from the west, to generate the large deep "hollow" (valley), would have taken quite some time and probably started at the earlier low sea level stand some 220,000 years ago or even earlier. To the west side of the lake there are also signs of the Newcastle coal measures.
At the end of the Triassic time, the area was uplifted to become dry land and erosion continued to take place. With the melting of the last glacial age some 16,000 years ago the area become flooded with rising sea levels and formed our current coast lines. Prior to the sea level rise from the glacial melt the coastline was about 15 kms to seaward of the present shoreline. Sand was moved onshore after this melt to form the Belmont peninsular and Swansea flat lands and so close off the wide mouthed embayment. Subsequent flooding rains would have necessitated an opening to the sea and hence the Swansea channel - which has probably moved north and south several times over the subsequent period. This also explains why the lake is so shallow as sand washed in from the ocean, and some silt from the catchment, has filled the original deeper hollow developed when sea level was some 30 to 100 metres lower. Sea level reached its present level at about 6,000 years ago, and the Belmont sand dunes and lake floor silt have accumulated in the last 6,000 years.
In order to log this earth cache answer the following questions via email per our contact details and include the Earth Cache Title
1. From the information at GZ what is the foreshore perimeter length
2. What is the maximum and average lake depth.
3. There are four landmark points on the lake identified by the sign. Provide the bearing (via your GPSr) to the land mark that has a name sounding like is might be associated with the Newcastle COAL measures (Don't take the bearing to the compressed picture on the sign but take it to the physical location).
4.The area is well known for a particular sailing boat. If boat capsizes with either the full height No.1 mast or No.2 mast and goes turtle will the mast touch the bottom of the lake for the maximum depth and average depth in Question 2.
Congratulations to Marcus Vitruvius for a speedy FTF