 Throughout most of the park the Hawkesbury and Wianamatta series have been eroded away exposing the Narrabeen group.The landscape of the park is dominated by deep valleys, canyons, cliffs and waterfalls, formed by the weathering of the sandstone and claystone the Narrabeen group consists of.The parts of the park that lie on the Narrabeen and Hawkesbury sandstones generally have shallow soil with low nutrient levels while areas that lie on the Wianamatta shale usually have deeper and more nutrient rich soils allowing for a greater diversity of plant life.