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 no 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 subordinate and the structure is more chaotic. The principal joints in this section 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 'entablature' and the upper is typically 'disorganised', 'massive' or 'scoriaceous'.

SITE SENSITIVITY, THREATS, POTENTIAL UTILISATION

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 gained 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 blocks 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:

Ollier, C.D. 1969, Volcanoes. A.N.U. Press, Canberra.

Photograph 5 Weathering detail at Site 4, Quarries Park. Photo Neville Rosengren approx 1993