Sedimentary volcanoes; overview and implications for the definition of a volcano on Earth

In contrast to volcanologists, sedimentologists are not only interested in "classical" volcanoes, but also in a second type, viz. sedimentary volcanoes. This type of volcano is helpful for sedimentologists in understanding the processes that occur in the (commonly unconsolidated) subsoil, even after deep burial. Sedimentary volcanoes can be grouped in three classes: mud volcanoes, sand volcanoes, and associated structures such as water-escape and gas-escape structures. Mud volcanoes on deep-sea floors can become partially abraded in the course of time by ocean currents, and then are recognizable on seismic profiles as so-called pockmarks. A brief review of the various types of sedimentary volcanoes is provided, and representative examples of an active mud volcano and of a dormant mud volcano are dealt with in some more detail. Sedimentary volcanoes have several characteristics in common with "classical" volcanoes, including their shapes and the processes that contribute to their genesis; they therefore deserve the name volcanoes, which implies that the term volcano has to be redefined.