Lord Howe Island
- ISS006-E-5731
- 02 December 2002
- 02:01
The Lord Howe group are the highly eroded remnants of a once ancient shield volcano that was active over a period stretching from 500,000 to 7 million years ago. On a larger scale the Lord Howe seamount is but one of a chain of submarine seamounts that extend across the floor of the Tasman Sea for over 1,000 km in a southeast to northwest direction forming a feature known as the Lord Howe Rise. Today, the main island and its offshore islets are the only emergent parts of the Lord Howe seamount — a 65 km by 24 km mass that rises 1,800 m from the ocean floor at the northeastern end of the Rise. The upper slopes of the seamount create a shallow shelf region (less than 50 m in depth) that surrounds the islands.
The main island of the group is that of Lord Howe Island itself. The island forms an open-crescent shape, measuring 10 km in length and 1.5 to 2 km in width. The southern end of the island is dominated by the steep to vertical sided peaks of Mount Gower (875 m) and Mount Lidgbird (777 m) that drop dramatically to the sea. These mountains (sufficiently high enough to support cloud forest on their summits) represent the walls of the former caldera of the long-extinct Lord Howe volcano that is estimated to have been 5 km across. The northern end of the island consists of steep slopes that rise to the largely cliff-lined edges of the northern coastline. Connecting the high northern and southern ends of the island is a low and narrow central region that contains the islands only flat land. The inner curve (west side) of the island shelters a shallow lagoon that is fringed by a 6 km long coral reef — one of the southernmost coral reefs in the world. Coastal areas facing the lagoon are low, with sweeping beaches of sand; those around the remainder of the island consist of sheer cliffs (reaching up to 200 m in height), hilly slopes and rocky headlands with a few small sandy coves occurring on the northern and central sections.
Located around Lord Howe Island are a number of small islets and islet groups. These include: the Admiralty Islands to the northeast (Roach Island, Noddy Island, South Island Tenth of June Island, North Rock, Flat Rock and several smaller rocky islets); Mutton Bird Island and its small partner Sail Rock, Blackburn Island (within the lagoon) and Gower Island (off the southern extremity of the island, King Point). Most spectacular of the minor islands is that of Ball's Pyramid — a 650 m tall, pyramid-shaped spire of rock emerging vertically from the water — located 23 km southeast from Lord Howe Island. Around Balls Pyramid are a number of emergent rocks and islets, including Wheatsheaf Islet and Observatory Rock.
Protected as a World Heritage Site since 1982, Lord Howe Island has an ecosystem that has been relatively undisturbed since settlement. The islands occupy a transition zone between temperate and sub-tropical regions — a fact that is reflected in the unique flora and fauna of the island. The lagoon and reef contain some 65 species of coral and over 500 species of fish. 240 native species of vascular plants are found, with over 100 of these being endemic. There are also 164 bird species (many endemic) with the islands representing one of the most important sites for breeding seabirds in the southwest Pacific region.
