Grains on an Exposed Gravel Bar (IMAGE) University of Leicester Caption This is a complex structural arrangement of grains on an exposed gravel bar, River Elan, Wales. The upper inset shows a small-scale bedform known as a pebble cluster (note keys for scale). The lower inset shows an extract of a high resolution survey of the bed microtopography derived using laser scanning technology. Credit University of Leicester Usage Restrictions Use only with credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.