Organ Pipes       ML16

(Melbourne 1:250 000 geological map)

Incision of Jacksons Creek has exposed a variety of features in the late Cainozoic Newer Volcanics that overlie Tertiary sand and gravel, and Palaeozoic bedrock. The Organ Pipes are a spectacular example of columnar jointing, which developed as the basalts cooled. The columns are both vertical and inclined and in an adjacent cliff section have formed a rosette. Other volcanic features include a tessellated pavement, spheroidal weathering and an eroded scoria cone. The volcanics are part of the basaltic icelandite field erupted in the Pliocene (2.5–2.8 Ma) which extends from Diggers Rest to Williamstown.

This excellent example of columnar basalt and other volcanic features is a good teaching site because of the range of volcanic features, exposure of the local geology and accessibility. The Organ Pipes National Park protects not only the geological features but also the largest and least modified area of volcanic plains grasslands and shrublands west of Melbourne. However, tree planting has obscured the view of the Organ Pipes from along the valley, and is beginning to limit visibility from the main observation point of the Organ Pipes themselves.

The Organ Pipes feature is an excellent example of columnar basalt and is used as a teaching locality. Planting of trees has obscured the view of the Organ Pipes feature from the main observation area.

More sympathetic management for geological values is needed.