View looking southwards past the terminus of the glacier Solheimajokull, Iceland, from an adjacent hillside in 1990. The Landrover parked on the river bank at the top right of the photo gives an indication of scale. The proglacial area is marked by numerous ice-block scour marks and kettle holes up to 5m in diameter and 2m deep. These are created by fragments of glacier ice that become entrained in minor outbursts of water and sediment from the glacier. The ice blocks affect the erosion and deposition of sediment by the floodwaters, and then are either washed away in the flow as they gradually melt, or melt away on the outwash plain after the flood has subsided. The largest examples are highlighted in the lower right of the photo, and others can be seen on the left of the photo nearer to the glacier. The outbursts with which these features are associated can occur for a variety of reasons, but in this case arose from the temporary blockage and subsequent sudden release of water emerging from a tunnel beneath the snout of the glacier. Volcanic activity can produce much larger floods, but the  extent of ice-block marking on the outwash plain is controlled not not  simply the size of the flood, but by a range of factors including the sizes of the ice blocks produced by the glacier and the concentration of debris in the floodwaters. Paradoxically, larger (deeper) floods might produce less ice-block impact.
    Also note the confluence and parallel in-stream flow of sediment-rich (grey) glacier meltwater and clear (blue) non-glacial water immediately below the position of the landrover.



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