Gulaga – In The Beginning

Gulaga (Mt Dromedary)

In the Early Cretaceous period (about 140 million years ago) the final breakup of Gondwana began with rupturing and rifting on its eastern margin, which led to the separation of New Zealand and the formation of the Tasman Sea. Igneous activity (rocks formed from molten magma or lava) is associated with this rupturing and the Gulaga Igneous Complex is one of a number of volcanoes which formed along the newly created eastern Australian margin at this time.

At Gulaga 98 million years ago, a very large stratovolcano formed. Stratovolcanoes are a steep conic form built up by interlayered lava and ash flows. The volcano was probably at least 2-3000 metres high with the summit and main mass of the cone to the east of Gulaga. The majority of the thick accumulation of erupted material is now eroded away but remnant lavas and tuffs (volcanic ash deposits) can be found east of Gulaga near Tilba Tilba Lake and at the northern end of Baranguba -pronounce Bar/ran/goo/ba- ( Montague Island ).After the eruptive volcanic stage the last major phase of igneous activity was the intrusion of a number of magma bodies under the lavas and tuffs, with the largest intrusive mass being at Gulaga and smaller masses at Najanuga-pronounce Na/ja/nook/a -(Little Dromedary Mountain) and the southern portion of Baranguba.

These magma bodies did not reach the surface, they cooled more slowly allowing the growth of larger mineral crystals and producing rocks more like granite than eruptive rocks. Because of the chemistry of the magmas these granite-like rocks are called banatite and monzonite and being much more resistant to erosion than the lavas and tuffs, they are left as remnant high points after erosion has removed most of the lavas and tuffs.

Gulaga is today a mountain with an altitude of 797 metres (2500 feet).