World’s Soil Resources

15.1 | Introduction
The Southwest Pacific region includes the 22 island nations of the Pacific1, New Zealand and Australia
(Figure 15.1). The landscapes of the region are very diverse ranging from a large continental land mass through
to tens of thousands of small islands across the enormous expanse of the southwest Pacific Ocean. There
are extensive ancient flat lands through to some of the youngest and most tectonically active landscapes on
the planet. Temperature and rainfall ranges are large because of the breadth of latitudes and elevations. As a
consequence, the soils of the region are also diverse. The strongly weathered soils in humid tropical areas and
the vast expanses of old soils across the Australian continent are particularly susceptible to disturbance and
this is where some of the more intractable problems of soil management occur today.
15.2 | The major land types in the region
The major land types in the region owe their origin to the relative movement of the Earth’s lithospheric
plates, and in particular to the interaction between the Australian and Pacific Plates. The breakup of the
supercontinent of Gondwana included the separation, around 96 million years ago, of the Australian Plate
from the Antarctic Plate. The Australian Plate includes the present day island continent of Australia, Papua
New Guinea, a small part of the South Island of New Zealand, and some islands including New Caledonia
and Norfolk Island. The Australian Plate is moving northwards at approximately 70 mm yr -1 , colliding with the
Eurasian Plate. This has created the mountains of Indonesia and Papua New Guinea, the highest peaks being
Puncak Jaya (4 848 m) and Mt Wilhelm (4 509 m) respectively. The Pacific Plate is moving westwards towards
the Australian Plate. Movement along the transform boundary of these plates has created the Southern Alps
of New Zealand (Aoraki/Mt Cook 3 724 m) and related geological activity has resulted in substantial volcanic
activity around the aptly named Pacific Rim of Fire. New Zealand straddles the boundary of the Australian and
Pacific Plate. Most of the island nations of the Pacific are volcanic in origin and exist today as either hilly or
mountainous features formed by the volcanoes themselves, or as atoll islands.
1 These countries are American Samoa, Cook Islands, Federated States of Micronesia, Fiji, French Polynesia, Guam, Kiribati, Marshall Islands, Nauru, New
Caledonia, Niue, Northern Mariana Islands, Palau, Papua New Guinea, Pitcairn Islands, Samoa, Solomon Islands, Tokelau, Tonga, Tuvalu, Vanuatu, and Wallis
and Futuna.
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in the Southwest Pacific