Sb9 Mount Holden - Eruption Point

This information has been developed from the publications:

Sites of Geological and Geomorphological Significance in the Western Region of Melbourne (1986) by Neville Rosengren
Sites of Geological and Geomorphological Significance on the Coast of Port Phillip Bay (1988) by Neville Rosengren.
Sites of Geological and Geomorphological Significance in the Shire of Otway (1984) by Neville Rosengren.

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 (external link) for details of geological heritage reports, and a bibliography.

Location	Sunbury - 964400. Shire of Bulla. North of Calder Highway 2 km west of Sunbury.	Sb9 - Lava ridges, Mt Holden.
Access	Reservoir Road
Ownership	Private land
Site Description	Mount Holden (412 m) is one of the most prominent of the eroded volcanic hills between Sunbury and Gisborne. It has a complex summit with rocky cliffs and ridges facing east and a gentler western slope with fewer outcrops. The outcrops are the last of the lava flows from the summit area of the volcano, the vent becoming infilled with this solidified lava and surrounded by a rim of scoria. Erosion has since removed the scoria, leaving the rims of lava around the summit which obscure the vent of the volcano.
	The eruption occurred in an area of hilly terrain developed on Ordovician sediments. These sediments have been exposed by Blink Creek which has stripped off the thin cover of lava so the volcanic material are now outliers almost surrounded by the older rocks.
Significance	Regional. The mountain has a more complex summit than the other volcanic hills in the district. The site shows the contrasting slopes produced by volcanic activity with the adjacent terrain developed on Ordovician sediments.
Management	Class 2. The site should be kept in rural land use or reserved for use as a public open space system. Buildings should not be permitted above the 330 m contour as this would detract from the significant form of the volcano.

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