Geologically and topographically PNG is very new. It is situated in a zone where the earth's crust is very weak, on the boundary between the tectonic plates of Australia and the Pacific Ocean. Most of the country has been formed by comparatively recent earth movements and volcanic activity.

The coastal and island regions tend to be hot and humid. Some areas in the south (including Prot Moresby) have a distinct rainy and dry season. Other southern coastal areas (including Madang and Morobe) have a less clearly defined wet season.

The overall appearance of the country is extremely rugged, particularly in the highlands which are characterised by sheer slopes, sharp ridges, fast-running rivers and the scars of countless landslides.

The highlands regions can be quite cold at night, although the days are usually warm and clear. A typical highland cloud cycle takes place each day - clear in the morning with some local fogs followed by an increasing cloud buildup. Afterrnoon rains are common.

The dominant feature of the country is the central spine of mountains through the island of New Guinea, a complex of high mountain ranges intersected by valleys and plateaus.

The mainland ranges from open beaches to coastal swamps and rough, fjord-like areas in Oro Province to dry Savannah country in the Markham and Ramu Valleys and the steep mountains of the highlands. The highest mountain in PNG is Mt Wilhelm (4000 metres).

There are few large valleys in the Papuan region, but the New Guinea region in the northern part of the mainland has several large open valleys such as the Asaro, Jimi and Wahgi, providing excellent agricultural and pastoral land. There are many small offshore islands, many without fresh water.

Island provinces are located off the tip of Papua with a cluster of islands forming the Milne Bay Province. To the north of the New Guinea mianland are the island provincws of Manus, New Ireland, East New Britain, West New Britain and North Solomons (Bougainville). All island provinces are noted for their coral reefs, beaches, rich volcanic soil and abundance of marine resources. The islands of New Britain and Bougainville have active volcanoes and experience earthquakes of up to 5 on the Richter scale. A volcano erupted in 1994, destroying much of the town of Rabaul in New Britain.