A volcaniclastic sediment is a sediment (regardless of average grain or clast size) composed primarily of volcanic material. This material may be pyroclastic (fragments derived from explosive volcanism) or hyaloclastic (fragments formed by thermal shock when hot lava comes in contact with cool sea or lake water). Undisturbed clastic deposits of volcanic materials are called volcanoclastic; the term sediment is added when the material has been reworked and redeposited by water, wind, or gravity. Volcaniclastic sediments have a wide range of compositions, from basalt (rarely komatiite) to rhyolite. They may display sedimentary features familiar from siliciclastic sediments, such as graded or cross bedding. Commonly, volcanoclastic sediment undergoes metasomatism or diagenetic changes, including carbonatization or silicification, for example, by hydrothermal fluids.