Islands are special places that capture something in the imagination of all people. Many islands in the world have turquoise lagoons, white sandy beaches and verdant forest clad mountain slopes, but very few have the charm of Lord Howe Island.
Environmental management of Lord Howe Island has been and still is exceptional. Early recognition of the uniqueness of Lord Howe Island by the state government of New South Wales has meant over a century of environmental management. This culminated in 1982 with recognition of Lord Howe Island as a World Heritage Site. More than 85 percent of the Island is still covered in its native forest, seventy percent of the Island is completely protected in a Permanent Park Preserve; a Marine Park extends twelve nautical miles all around the Island; both the Administration Board and the local population are keen to see the Island environment preserved at all costs.
This dramatic landscape was formed by volcanic activity between 6 and 7 million years ago, which thrust up a large shield volcano from the seabed – originally reaching a diameter of 30 kilometres and an estimated height of 1000 metres above sea level. However, the Island of today is the result of massive erosion of the original volcano, which has been reduced to just 2 percent of its original size, carved and sculpted by prevailing winds and ocean swells, constantly attacking rock layers of varying thickness and resistance.
The formation of coral sands, together with the action of plants, are more recent influences which helped shape the Island’s current form. Today, two towering mountains dominate the landscape rising to 777 and 875 metres from the ocean, making up approximately two thirds of the Island’s total land area. The mountains are flanked by shear black basalt cliffs and steeply forested slopes. The northern part of the island is formed by a series of low hills which slope gently up from the west to a height of around 200 metres, then plunge vertically into the sea as a line of steep cliffs. Several flat, low-lying, areas between the hills in the north and the mountains in the south make up the lowlands.
These lowlands and mountain slopes are carpeted with forests containing an amazing variety of plants, including four unique palm species. The Island is roughly crescent shaped, with the western concave side being bordered by a fringing coral reef 6 kilometres in length. A huge, shallow lagoon two to three metres deep is bounded on the landward side by a broad sandy beach, and on the seaward side by the fringing reef with its endless line of white breakers rolling off the Pacific Ocean swell. However, within the shallow lagoon, several deep holes have formed – named Comets, Erscott’s and Sylph’s Holes. Here, and elsewhere in the lagoon, coral outcrops are abundant, particularly towards the reef.
The main island of Lord Howe is surrounded by 27 smaller islets and rocks, the most spectacular of which is Ball’s Pyramid 23 kilometres to the southeast – reported to be the tallest rock “stack” in the world – its summit is 551 metres above sea level, its base is 1100 metres long and 400 metres wide. The Pyramid is a craggy, eroded remnant of an ancient volcanic island. From a distance it looks like a fairytale castle or a cathedral.
One of the most intriguing processes in nature is the colonisation of Islands by plants and animals. How do these tiny, remote specks in the ocean become populated by myriads of plants and animals? For centuries, it has been a source of wonder to explorers and scientists to discover how remote islands, thousands of kilometres from the nearest land, become populated by rich assemblies of living organisms.
Three methods have been identified as the principal means by which plants are dispersed over the oceans – wind, water and transport by birds.
Many seeds are tiny and can be blown hundreds of kilometres in wind currents; or larger seeds may have a parachute of silky hairs attached, enabling them to float on air currents over long distances. Some insects can similarly be blown in wind currents, or some spiders weave a parachute of silk for air transport.
Many oceanic island plants have arrived as seeds that float; they must be buoyant and have a tough seed coat to survive in sea water.
Birds can carry seeds in their stomach or on their feathers; and even carry eggs of snails or crustaceans on their feet.
Certain groups of plants and animals are specially adapted for long distance dispersal, and many islands in the Pacific share similar species or genera. For example the Mountain rose Metrsodideros nervulosa of Lord Howe Island has relatives across the Pacific to Hawaii. Metrosideros seeds are tiny and blow long distances in wind currents; plus they survive cold temperatures encountered as they are carried aloft by winds.
Lord Howe Island has a subtropical maritime climate. The seasons change gradually: Winters are cool and wet with even rainfall; summers are warm and mild with fairly high but less regular falls of rain. Daily maximum temperatures average around 25°C in the summer months to 18°C during winter. The minimum average temperatures are 19°C to 13°C over the same period.
Relative humidity varies little year round, generally being in the high sixties to seventies. The fact that Lord Howe Island is surrounded by the moderating effects of the ocean ensures the continuation of this moist, humid climate with its small daily and annual range in temperature and humidity.
Rainfall is seasonal, with about 180mm in June and July, and 120mm in the summer months. Most rainfall occurs as moderate to heavy showers and not continuous rain, but winter frontal systems can bring rain bands that may last for a day or more. The Summers are actually drier than the statistics indicate, because some years bring erratic tropical lows that can boost the average figures by up to 300mm in a month. Water temperatures around the Island vary from a low of 17°C in August to 25°C in March, although the lagoon can be warmer on sunny days. Generally, conditions are mild enough to enjoy swimming between the months of November and May.
Lord Howe Island and Ball’s Pyramid are the last remnants of two volcanic seamounts that formed around 7 million years ago.
Geologists believe that there were two main volcanic episodes in the formation of Lord Howe Island. Most of the volcanic activity took place some 6.9 million years ago, and comprised several volcanic vents, ultimately producing a large shield volcano about 30km in diameter. It is thought that the volcano’s maximum height above sea level was about 1,000 metres.
Around 6.3 million years ago the area around the main vent collapsed and left a huge oval-shaped pit or caldera, perhaps five kilometres long, two kilometres wide, and 900 metres deep. At this time further volcanic material pushed up from beneath the earth’s crust to infill the caldera in a series of horizontal lava flows, varying from one to thirty metres in thickness. In this second period of volcanic activity, the basalt rocks were harder and more erosion resistant, standing today as magnificent ramparts of the southern mountains which still rise to 875 metres above sea level.
Sedimentary rocks & fossils
Corals and coralline algae extract calcium carbonate from seawater, which they use to produce hard skeletons for protection. As these marine organisms die and crumble their fragments are ground up by the pounding action of waves and are wind-blown against the Island, forming beaches and dunes.
Over time, rainwater seeping through the sand has cemented the grains into a type of sandstone known as calcarenite. Around 25 percent of the Island, over much of what is the settlement area today, is in fact covered by this calcium carbonate-based sandstone.
Carbon dating of fossils in a number of the dune deposits suggests an age of 20,000 to 40,000 years, but it is believed that the calcarenite beach deposits behind Ned’s Beach were formed in the last interglacial period around 130,000 years ago when sea levels were roughly the same as they are at present.
While these ancient beaches were forming, the now extinct horned turtle, Meiolania platyceps, was roaming Lord Howe Island. Its bones have been found as fossils, in the soft calcarenite rock. Meiolania platyceps is one of a group of bizarre fossil turtles of prehistoric appearance, having horns on the skull, and a long tail with bony rings and a heavy terminal club. The meiolaniid group of turtles is known only from Southern Hemisphere locations — Lord Howe Island, New Caledonia, mainland Australia and Argentina.
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