This is a photo of lahar deposits near Santa Maria volcano (Guatemala). This used to be a wide, deep river valley, and you can see the far wall of the valley where the trees are growing. The lahar deposits extend from that far wall to behind where this photo was taken. You can see that between lahar events the river cuts into the lahar deposits, but every time there is another event, it fills up again. The people give an idea of the size of stones that can be carried by a lahar.
This photo give somewhat of an idea about the distance that lahars can travel. This photo was taken some 15 km from the base of Santa maria, and the plain of lahar material has filled the river valley and spread to a width of almost a kilometer. The truck that is driving across the deposit gives a sense of the size of stones that can be carried even this far. In the distance is Santa Maria volcano. The scar that formed from the big 1902 eruption is clearly visible because it does not support vegetation. In this photo Santiaguito dome has just had a small eruption.
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