What are Lahars?
A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. Lahars are extremely destructive natural phenomena that can occur with little or no warning. Some of the most devastating volcanic eruptions in history have been accompanied by powerful lahars that have swept away entire towns and villages.
Lahars typically form when heavy rains fall on loose volcanic ash and other debris that has accumulated on the slopes of a volcano. The resulting mixture of water, rock, and ash can become highly unstable and move downslope at high speeds, causing immense damage in its path. Lahars can also form during an eruption when hot lava mixes with cold water, creating an even more dangerous and fast-moving mudflow.
While lahars are often associated with volcanoes, they can also occur after earthquakes or other landslides that disrupt the stability of slope materials. In some cases, lahars have been known to travel for dozens of kilometres from their source before finally coming to rest.
The word “lahar” is derived from the Indonesian word for “mudflow”. Lahars are common in Indonesia due to the many active volcanoes in the region (such as Mount Merapi) and the frequent occurrence of large earthquakes that can trigger landslides. However, lahars are not limited to Indonesia; they have also caused extensive damage in other parts of the world including Peru, Chile, Japan, Russia, Alaska (USA), Canada, New Zealand, Philippines and Italy .
Most people caught in a lahar will die due to suffocation or crushing injuries long before they reach any kind of safety. For this reason it is important to be aware of the dangers posed by these deadly flows and take steps to protect yourself and your loved ones if you live near an active volcano.
Some of the best ways to protect yourself from a lahar are to:
- Know the signs that a lahar might be coming. These can include an earthquake, changes in water level or flow, and unusual sounds coming from the volcano.
- Have an evacuation plan ready and know the safest route to high ground.
- Avoid areas downstream of a volcano that could be at risk of being inundated by a lahar.
- Stay informed about the latest conditions and warnings from authorities.
