Frederick Reefs - General Description

General Description

The Frederick Reefs are a small group of remote reefs located beyond the southern reaches of the Great Barrier Reef,

The reef complex lies 540 kilometres (340 mi) due east from the city of Mackay, Queensland or 450 kilometres (280 mi) northeast of the city of Gladstone. The reefs are part of the southern reefs of the Coral Sea and as such are located in deep oceanic waters off the Coral Sea Shelf.

Aside from its costal neighbours, it also lies 175 kilometres (109 mi) east from the Swains Reefs; the lower part of the Great Barrier Reef. Frederick Reefs is approximately 95 kilometres (59 mi) northeast of the Saumarez Reefs and 120 kilometres (75 mi) west of the northwest extremity of Kenn Reefs.

The reefs form a semi-enclosed lagoon or body of water known as Anchorage Sound; protected on most sides but open on the north side. On the southern side of the reef lies Observatory Cay, (21°02'S., 154°23'E.), the only permanently dry land, although there are a few of others cays that can be awash at high tide. Observatory Cay is approximately 1.8 metres (5.9 ft) above sea level; with a possible landing site on its northern side through a boat channel which leads in from North East through the reef. As the cay lies near the southern edge of the reef, the surf sometimes breaks over it in heavy gales.

Similar to other smaller sand cays and spits, the position of the sand spit can move. In 1983, it was reported that Observatory Cay lay about 750 metres (2,460 ft) west of the charted position. It has also been reported that the reef complex has at least 4 or 5 other sand cays on the southern reef which does not cover with water at high tide other than Observatory Cay.

A solitary leaning rock, 1.2 metres (3.9 ft) high, lies on the western extremity of the Observatory Cay southern reef, 2.4 kilometres (1.5 mi) west-northwest of Observatory Cay.

From Observatory Cay, the southern part of the reef extends to the north and northeast for 6.2 kilometres (3.9 mi).

Danger Ridge (21°00'S., 154°21'E.) is a narrow ridge connecting the western end of Observation Cay and Ridge Rock.

The North Reef Extreme is located to the north of Observatory Cay with its southern extremity about 3 kilometres (1.9 mi) north southern extremity of the Observatory Cay reef. It is about 2.7 kilometres (1.7 mi) long and about 900 metres (3,000 ft) wide. A small cay ls located 900 metres (3,000 ft) south of Frederick Reef Light. The Light has a nominal range of 20 kilometres (12 mi), and stands at an elevation of 33 metres (108 ft)