WELCOME TO CAPE WOOLAMAI FORMALLY KNOWN AS SNAPPER HEAD
Cape Woolamai has a special geological feature that are mentioned in the below extract from Victorian Resources Online
Cape Woolamai is part of a tombolo system that includes the predominantly granitic mass of the cape and the complex of volcanic rocks,. Sediments, beach material and dunes that links the granite with the main body of Phillip Island. Woolamai Hill is the highest point on Phillip Island and the surface of the cape slopes gradually towards the north at an average angle of 5o (Edwards 1945). The main body of Cape Woolamai is a small stock of pink, coarse, porphyritic, potassium rich material known as the Cape Woolamai Granite (Tattam, 1976). The rock is well exposed in coastal cliffs and on the south-western coast, eg at the Pinnacles, these cliffs are of spectacular form and dimension. Strong jointing has determined the orientation of gutters and deep clefts that have been eroded in the cliff face and base, and produced the pyramidal rock stacks and large boulders that are typical of the exposed southern coastlines. The shoreline is also notable for the lack of horizontal platform development (Edwards 1942, 1945). The northern coastline facing the Eastern Entrance is more subdued in form and here a small disused quarry provides accessible exposures of the granite materials.
The upland surface of Cape Woolamai is covered by calcareous and quartzose sands and occasional patches of dune calcarenite. The sands are aligned in parabolic formations and parallel intersecting sets that differ considerably in their orientation from that to be expected by analysis of present wind regimes (Teh 1973). Jenkin (1962) explained the parallel sets are related to jointing in the granite and Teh (1973) suggested that the burrowing habit of Mutton Birds (Puffinus tenuirostris) has in part determined the orientation of the older parabolic dunes.
Cape Woolamai is a very distinctive landform and a class example of a former island now linked to a larger land mass to form a tombolo system. The granite cliffs are amongst the highest on the Victorian coast and the diverse array of storm environment features on the southern coast contrast markedly with those of the sheltered Eastern Passage shore. The upland dune features are unique in Victoria and provide an unusual example on a national scale of the multiple processes that shape dune sands.
The area between Cat Bay and Summerland Bay is a double tombolo formation that links the former Summerland’s Island to the main body of Phillip Island. The tombolo base has been built upward by the growth of beach ridges and transgressive dunes from both the northern (Western Port) and southern (Bass Strait) shores. These sand bodies have not coalesced however and they enclose a swampy lowland including the open water area of Swan Lake. This site includes part of the wetland and the dunes of the southern tombolo. This is the best example of double tombolo formation on the Victorian coast. Stages in the reclamation of the former seaway may be determined by a study of the dune and wetland systems.
WHAT IS A TOMBOLO?
A tombolo, from the Italian tombolo, derived from the Latin tumulus, meaning 'mound', and sometimes translated as ayre (Old Norse eyrr, meaning gravel beach), is a deposition landform in which an island is attached to the mainland by a narrow piece of land such as a spit or bar. Once attached, the island is then known as a tied island. Several islands tied together by bars which rise above the water level are called a tombolo cluster. Two or more tombolo's may form an enclosure (called a lagoon) that can eventually fill with sediment. A tombolo may be considered to be a type of isthmus.
HOW ARE TOMBOLO'S FORMED
True tombolo's are formed by wave refraction. As waves near an island, they are slowed by the shallow water surrounding it. These waves then refract or bend around the island to the opposite side as they approach. The wave pattern created by this water movement causes a convergence of long shore drifting on the opposite side of the island. The beach sediments that are moving by lateral transport on the lee side of the island will accumulate there, conforming to the shape of the wave pattern. In other words, the waves sweep sediment together from both sides. Eventually, when enough sediment has built up, the beach shoreline, known as a spit, will connect with an island and form a tombolo.
LOGGING REQUIREMENTS
No1 What is a Tombolo?
No2 These granite cliffs of Cape Woolamai are amongst the highest in Victoria near GZ is a plaque it will tell you how high you are.
No3 Grab your compass, face directly west while at GZ. Now can you tell me what is the nearest geological feature you can see in the distance and is it a Tombolo?
No4 Is Cape Woolamai the only Tombolo on Phillip Island ?
Please email me your answers.
ACCESS TO THE EARTHCACHE
To access this earthcahe you will need to park at the Woolamai Surf Beach carpark. Please if it is warm take plenty of water with you. The tracks out to GZ are pretty well marked but do keep an eye out for snakes. You need to allow a few hours to complete the walks out here but it is well worth it . A huge thanks to Hearse068 and BorisB&Natasha for taking the time to come with me and experience this great area. Don't for get to take a camera with you as you will find lots of spots for photos.