The park is very distinctly split by the main divide of the South Island. The eastern side is typically drier and consists of beech forest and wide riverbeds, while the western side contains dense rainforest. Much of the geography was formed by ancient glacial action, forming flat bottomed U-shaped valleys. In the middle is a high range, consisting of large, snow-covered peaks and scree slopes. The park contains the following geographical features:
Arthur's Pass National Park has a reputation as one of the most dangerous national parks in New Zealand. In the first three months of 2006 alone two people died whilst walking in the park. Whilst no formal studies have been conducted, amongst the tramping community and the permanent Arthur's Pass community it is felt that the combination of harsh alpine terrain and easy accessibility combine to contribute to the high death and injury rate. The mountains around Arthur's Pass contain some very challenging terrain. The marked day walks in the park, all easily accessible from the Arthur's Pass village carparks, involve vertical ascents of around 1000 metres and include several hours well above the tree line. The peaks are highly exposed to the weather, the tracks are often very steep and are often marked only by poles strung across a rocky landscape. Below the tree line the bush is dense and thick. In common with many alpine areas the weather is subject to frequent and sudden change. There are frequent bluffs and cliffs and most creeks running down the mountains tumble over waterfalls in one place or another. Further, there are a number of harder routes within the park that require a high level of mountaineering skill and the use of ropes and other such equipment. In short, safely traversing the terrain requires at least a moderate level of experience, knowledge and equipment as it is true 'back country'. Arthur's Pass National Park is also within a few hours' driving time of Christchurch, the largest city in the South Island of New Zealand. This easy access for visitors to New Zealand, as well as the immediate access to the mountain trails from the village appears to lead to larger numbers of unprepared persons overstepping their abilities and getting into mortal peril. The most common scenarios are: persons caught above the tree line in bad weather with insufficient clothing and/or food then suffer from hypothermia; persons attempt a climb that requires knowledge or equipment they do not possess and often become stuck on a ledge or cliff, unable to climb back or continue on due to the steepness of the terrain, often then facing the problems of bad weather/hypothermia; persons attempt a climb that requires knowledge or equipment they do not possess and attempt a manoeuvre that result in a serious or fatal fall; persons become lost or disoriented, often due to change of weather, lose the trail or attempt to take a shortcut and suffer a serious or fatal fall.
