Geology
The formation of the area began with muddy sediments under ancient oceans that were changed by heat and pressure into hard rocks, then uplifted by movements of the continental plate and volcanic eruptions. This resulted in the formation of the Great Dividing Range, an undulating plateau that sloped gently to the west and fell away steeply to the east.
Erosion by wind, rain, storms and ice over millions of years carved out the plateaus of the Northern Tablelands, and rivers and streams gradually cut back the eastern edge of the tableland creating deep gorges that eventually formed one continuous escarpment. The jagged scarp is slowly retreating west and this movement can be seen today in the erosion of steep cliffs at places like Wollomombi, Dangars and Apsley Gorges.
Read more about this topic: Oxley Wild Rivers National Park