The Vegetation of New Zealand
3. Physical Features of the Outlying Islands
3. Physical Features of the Outlying Islands.
The Kermadec Islands. These are four in number. They extend from 29° 15' S. lat. and 177° 59° W. long, to 31° 24' S. lat. and 178° 51' W. long., and are distant about 960 km. from New Zealand. The group is volcanic, but it stands on a submerged plateau, part of a ridge connecting New Zealand with Tonga. Outside the plateau the ocean is 2700 m. deep.
Sunday Island, the largest of the group, 10.3 km. long and 29.25 sq. km. in area, reaches a height of 524 m. It is composed chiefly of pumiceous and other tuffs; lava streams are few. The surface is hilly with many narrow spurs separating deep gullies. These spurs, truncated at the coast, drop as sheer precipices to the water for 200 to 300 m. The greater part of the island is a crater, its rim 55 m. above sea-level in the north but elsewhere averaging over 300 m. There are three small crater lakes. There is a small sandy beach and one of gravel.
Macauley Island, distant 109 km. from Sunday Island, is 2 km. long, 3 sq. km. in area, and its highest point 237 m. above sea-level. Cliffs everywhere fall to the sea.
Curtis Island, 35 km. from the last-named, are two rocky islets with an area of 0.6 sq. km. and the highest point 100 m. The crater-floor contains hot mud, boiling springs and sulphur. (All the above is taken from Oliver 1910).
The Chatham Islands. These consist of four islands and several detached islets and rocks, lying between the parallels of 43° 35' and 44° 25' S. lat., and the meridians of 176° and 176° 55' W. long, and distant 600 km. from New Zealand proper. Chatham Island, by far the largest of the group, is 967 sq. km. in area and is somewhat the shape of a horseshoe. Generally the land is low but undulating. Much of the interior is occupied by the Te Whanga lagoon which, roughly triangular extends from the north coast southwards for 25 km., and, at its greatest breadth, is nearly 15 km. wide. On the east, it is separated from the sea by a very narrow strip of land broken through at one point. South of the lagoon the island is a compact four-sided block, which, in comparison with the remaining land, looks quite hilly, but its highest part is only 286 m. and the culminating point of the page 49main ridge about 2 m. lower. From this ridge a tableland extends southwards terminating in abrupt cliffs 182 to 213 m. in depth irregularly cut by small streams. Here and there conical volcanic hills, 152 to 182 m. high, stand out from the flat, northern and central portions of the island.
The extensive coast-line varies from flat ground bordered by dunes or low rocks to the high cliffs of the south and south-west.
Besides the Whanga, there are many other lagoons and lakes, indeed, it is stated that one-third of the surface is occupied by water. Bogs of great extent and depth are a familiar feature both of high and low ground. Small, sluggish streams of peaty dark-brown water are. abundant.
Pitt Island, 13.6 km. long by 6 km. across, lies about 22 km. to the south of the main island. Its coast is rocky. The remaining islands (Mangere, South-East Island) are quite small, but the latter rises to 184 m.
The New Zealand Subantarctic Islands. These consist of several distant groups lying between the parallels of 45° 44' and 47° 43' S. lat. and 158° 56' and 179° W. long. The names, distance and direction of each group from the South Cape of Stewart Island are as follows: Snares, 113 km., S. S. W.; Lord Auckland Islands, 348 km., S. by W.; Campbell Islands, 608 km., S. by E; Macquarie Islands, 1049 km., S. W. by S.; Antipodes Island, 902 km., E. S. E.; Bounty Islands, 902 km., E.
All the islands, excepting the Bounties and the Snares, are chiefly of volcanic origin and, the Bounties excepted, the surface consists in general of a deep layer of peat.
The Snares consist of North-East Island, 1.6 km. long and 0.8 km. wide, which rises perpendicularly on its south side to 131 m. and of four other rocky islets lying to the south-west. The main island has a rocky precipitous coast-line except in one place on the east side where a small stream enters the sea. The island is formed of a pale moderately-coarse muscovite granite.
The Lord Auckland Islands consist of two fairly large islands, Lord Auckland Island, 40 km. long by 27 km. wide in its widest part and Adams Island 24 km. long and 8 km. wide in its widest part, together with a group of small islands to the north and the small precipitous Disappointment Island on the west. An elevation of 360 m. would connect the group with New Zealand proper.
Adams Island is separated from Lord Auckland Island by Carnley Harbour, the site of an old volcano. It is a fairly even ridge, 600 m. high, with a long slope northwards, but southwards descending to the sea in a sheer precipice.
Lord Auckland Island is also high and rises in more than one place to 600 m. Several arms from Carnley Harbour pierce it in the south. On the east are a number of small fiords the result of ice-action, but on the west there is a perpendicular wall of stupendous cliffs.
The islands in the north are separated from Lord Auckland Island by page 50Port Ross, a land-locked sheet of water. They are quite low but their coasts are rocky. On Enderby Island there is a sandy beach, 8 km. long backed by low dimes. Disappointment Island, some hundreds of metres high with cliffs on all sides is about 3 km. in length.
Rivers of considerable size for so small a land-area fill the valleys of the two larger islands. The watershed of Lord Auckland Island is close to the summit of the western cliffs. There are one or two small mountain lakes.
There is abundant evidence of glacial action, but according to Speight it is improbable that the islands have been completely covered by ice.
The Campbell Islands consist of a main island (Campbell Island) 48 km. in circumference, but the other members of the group are mere rocks. The northern end of the island rises as a whole to about 300 m., but in the south there are a number of isolated peaks, the highest being from 400 to 500 m. altitude. Two long inlets pierce the land on the east.
The rocks are in part volcanic and in part limestone containing fossils. According to Maeshall the surface-features are due to glacial action, but there is no evidence that the island was covered by an ice-sheet.
Macquarie Island, according to Scott (1883:486), is exceedingly hilly, the hills rising to perhaps 280 m., while numerous tarns lie amongst their hollows. The coast-line consists principally of cliffs with a few shingle beaches. Possibly the island is 30 km. long. The rocks, so far as known, are volcanic. Apparently the island is separated from the rest of the Subantarctic Group by the ocean's depth of no less than 3600 m.
The Antipodes Islands consist of Antipodes Island (8 km. long by 4.6 km. at its widest) and Bollons Island, quite small, but 150 m. high. The surface of the main island is an undulating plateau, Mt. Galloway, the highest point reaching 530 m. The coast consists of high, perpendicular cliffs. The rocks, so far as known, are basalts.
The Bounty Islands are a small group of rocky islets and rocks formed of a pale biotite granite. The largest island is 1 km. long by 0.8 km. wide and 88 m. high. The surface is without a true soil and is polished smooth as glass by thousands of penguins and other birds, which live for part of the year on the island and numerous fur seals. Quantities of guano collect during the breeding season of the birds, but the greater part is removed by the rains of winter.