The southern cliffs in Springbrook (and Lamington National Park) are part of the remnants of the northern rim of the huge, ancient Tweed Volcano. The Springbrook National Park comprises four reserves on and around the plateau: Springbrook Plateau section along the crest of the plateau; Mount Cougal section to the east; and Natural Bridge and Numinbah sections to the west. The cliffs are resistant, volcanic based rhyolite. Rock overhangs are common and massive rock falls sometimes dislodge house-sized rocks.