Site 5 Northcote Park Football Ground - Basalt Columns

This information has been developed from one or more of these publications:

Sites of Environmental Significance in the Flood Plain of the Upper Yarra Valley Region (1983) by Neville Rosengren, Douglas Frood and Kim Lowe (as part of a study of Sites of Environmental Significance by the University of Melbourne for the then Upper Yarra Valley and Dandenong Ranges Authority).

Geological heritage sites, including sites of geomorphological interest and volcanic heritage sites, are under regular revision by the Geological Society of Australia, especially in the assessment of significance and values.Reference should be made to the most recent reports. See the Earth Science Heritage section of the Geological Society of Australia website for details of geological heritage reports, and a bibliography.

Location:	YARRA 5000/05.07 E24140 N16110
	Left bank of Merri Creek south of the Northcote Park Football Ground and 100 metres west of the Heidelberg Road bridge.
Access:	There is direct safe access to the site as it is a very steep cliff and there is some loose rock on the face. The site can be safely and satisfactorily viewed from the Merri Path on the right bank of the Merri Creek just upstream from the Heidelberg Road bridge.
Ownership & Municipality:	Public Land, City of Northcote.
Site Description:	The natural cliff at this very narrow part of the Merri creek gorge displays lava flows with contrasting orientations of vertical jointing. The lower half of the slope is a natural talus that is almost totally obscured by weed growth. Above the talus, a section several metres thick has well-defined vertical columnar structures cut by closely-spaced horizontal joints. Overlying this is thick section where vertical joints are inclined from the vertical so that the columns more resemble “post-piles”. The uppermost basalt is massive and vesicular and lacks any regular geometric fracturing.
Significance Rating:	Regional.
	This is an excellent example of a commonly observed sequence of joint fractures in basalt lava flows that divide the flow into three vertical divisions. The lower columnar section is known as a “colonnade”, the middle as an “entablatures” and the upper is typically “disorganised”, “massive” or “scoriaceous”.
Site Sensitivity:	Class 2.
	The site is robust but removal of loose or fallen blocks should not be permitted. Visitor access to the face should not be encouraged due to the hazard of falling or dislodging jointed blocks. It is not necessary to access the face to appreciate the nature of the geological features. A better appreciation of the sequence is grained from a vantage point on the opposite valley slope. A viewing platform here would facilitate this. A major threat is that tree and shrub growth on the lower slopes and weed invasions of the face will obscure the significant sections. Tree growth at the top near the edge of the cliff will lead to root-wedging of blacks and may cause collapse of some sectors. The site should be cleared of weed growth and trees removed or pruned to allow clear visibility from the right bank from the Merri Path. This would make an excellent interpretation site to complement a network of such sites in the Merri Creek gorge in Northcote and Collingwood.
References:	Ollider, C. D. (1969), Volcanoes, A.N.U. Press, Canberra

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