Mt Holden
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.
Source DPI
It was very hard to make sense of the geological history of the summit area as it is heavily eroded. The remaining features are predominantly lava with multiple outcroppings. There appears to be significant spatter ramparts on the southern edge of the summit area. There are also excellent views of the surrounding area. Low down, look out for the line dividing the scoria from the underlying (and much older) sedimentary deposits.
The public access from Phillip drive and the paths up the the mountain on the eastern side are under development and are likely to change.