Phillip Island Excursion Site 7: Smiths Beach quartzite

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Smiths Beach, Phillip Island
Smiths Beach, Phillip Island

You will need to walk on the beach about 500 metres east of the car park at the end of Smiths Beach Road to the rocky outcrops and the wave platforms. You can only see this feature at low tide.

You may be able to see an irregular ridge of tough, yellow-white quartzite, which protrudes from the basalt shore platform near the headland 500 metres east of Smiths Beach. The quartzite is strongly indurated (hardened) and is likely a layer of metamorphosed quartz sand that has been heated and hardened by the basalt lava. The outcrop is 2.5 metres high and 10 metres long. You may have trouble seeing the base of the material and its contact with the basalt because it is covered by the sea at most stages of the tide.

Some have explained the quartzite as originally being deposited as a quartz gravel in a valley on the north sloping valley side. It was later covered by the basalt flow. The basalt shore platform adjacent to the outcrop has a large domed structure with a radial fracture pattern resembling a lava blister.

Significance

This quartzite ridge is a most unusual structure and no equivalent feature is known on the Victorian Coast. It illustrates how sedimentation happened at the same time as the volcanic eruptions.

Guide available as a booklet
This entry is taken from the geological excursion guide for Phillip Island. The complete guide is available as a booklet on creation.com Aussie store.