One of the unusual and notable rock formations is the Casibari Boulders, which are tonalite rocks seen to the north of Hooiberg. They are reddish brown in colour and rise above the desert landscape giving a panoramic view of the island. They are located amidst cacti, and lizards are commonly encountered here. The boulders have unusual shapes resembling birds and dragons. There is no plausible explanation yet for the presence of these unusual wind-carved boulder formations on a flat sandy island. However, the geological formations seen on the island are of volcanic origin in its eastern sector, and some areas which are of coral formation are ascribed to the sea which was at higher level. However, in the diorite rock formation region, the Ayo Rock Formations are seen in a heap of monolithic boulders.