Tangiwai Railway Disaster

On Christmas Eve of 1953, a segment of the crater lake wall at the summit of Mount Ruapehu collapsed causing a massive mudslide or lake drainage filled with large boulders known as a lahar. Once a lahar begins to flow, it gains a lot of momentum and does not stop once it gets to the bottom of the volcano. It can continue flowing destroying anything in its path. This lahar continued past the mountain base and took out a railway bridge. An express train traveling to Auckland on this route was not warned of the gap in the bridge and went right over the edge leading to the death of 151 people. This tragedy is known as one of the largest disasters in New Zealand’s history. In the photograph, evidence of the lahar can be seen by the large boulders deposited in its path. The newly constructed railway bridge, which was built to avoid the path of a future lahar, can also be seen. Today, many geologists study and monitor the lahar paths and the status of Mount Ruapehu’s crater lake to prevent another catastrophic event from occurring. Although these precautions are being taken, danger still exists. The crater lake still contains a huge amount of water with a pH of 1 and a temperature of about 38ºC. The high acidity of the water adds to the erosion of the crater lake walls, which could ultimately lead to another lahar in the future.