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Lahars move rapidly down valleys like rivers of concrete. If you are on the floor of a valley that leads from a volcano and become aware of an oncoming lahar, seek high ground. Lahar is an Indonesian term that describes a hot or cold mixture of water and rock fragments that flows down the slopes of a volcano and typically enters a river valley.
Lahar is an Indonesian word meaning mudflow.. A lahar is a form of a mudslide, triggered most often by a volcanic eruption, which flows down the mountain.They are also called debris avalanches. As the lahar travels down the mountain, other debris such as rocks, logs, and trees become part of the fast moving mudslide.ahar is an Indonesian word meaning mudflow.. A lahar is a form of a mudslide, triggered most often by a volcanic eruption, which flows down the mountain.