Shag Rock (Houtman Abrolhos)

Shag Rock is a small rocky island in the Wallabi Group of the Houtman Abrolhos.

Geography
It is located at -28.47583°N, 113.71222°W, about 1.5 km east of West Wallabi Island. Its nearest neighbour is Plover Island, about 700 m away. The island has an area of about 0.1 ha, and a maximum elevation of 3 m. It is uninhabited, and devoid of human infrastructure.

This island should not be confused with the rocky island that lies to the west of North Island. The latter has no gazetted name, but is informally known as "Shag Rock".

Geology and physiography
Shag Rock is essentially an outcrop of Wallabi Limestone, a dense calcretised, coral limestone platform that underlies the entire Wallabi Group. This platform, which arises abruptly from a flat shelf, is about 40 m thick, and is of Quaternary origin. Reef that formed during the Eemian Stage (about 125,000 years ago), when sea levels were higher than at present, are now emergent in places, and constitute the basement of the group's "central platform" islands, of which Shag Island is one.

Flora
About half of the island, including most of its centre, is rock with no vegetation cover. A very small area just south of the centre is vegetated by Tecticornia halocnemoides (Shrubby Samphire). The remainder of the island, predominantly the northern third and a patch in the south west, is vegetated by Atriplex cinerea (Grey Saltbush), Nitraria billardierei (Nitre Bush) and Pittosporum phillyreoides (Weeping Pittosporum).