Peat is an accumulation of partially decayed vegetation matter. Peat forms in wetlands or peatlands.
A varve is an annual layer of sediment or sedimentary rock.
In oceanography, terrigenous sediments are those derived from the erosion of rocks on land; that is, that are derived from terrestrial environments. Consisting of sand, mud, and silt carried to sea by rivers, their composition is usually related to their source rocks; deposition of these sediments is largely limited to the continental shelf.
Volcanic ash that has fallen through the air from an eruption cloud. A deposit so formed is usually well sorted and layered.
A turbulent mixture of gas and rock fragments, most of which are ash-sized particles, ejected violently from a crater or fissure. The mass of pyroclastics is normally of very high temperature and moves rapidly down the slopes or even along a level surface.
Angular chunk of solid rock ejected during an eruption.
Fragment of molten or semi-molten rock, 2 1/2 inches to many feet in diameter, which is blown out during an eruption. Because of their plastic condition, bombs are often modified in shape during their flight or upon impact.
A rapid and unusually sudden sliding or flowage of unsorted masses of rock and other material. As applied to the major avalanche involved in the eruption of Mount St. Helens, a rapid mass movement that included fragmented cold and hot volcanic rock, water, snow, glacier ice, trees, and some hot pyroclastic material. Most of the May 18, 1980 deposits in the upper valley of the North Fork Toutle River and in the vicinity of Spirit Lake are from the debris avalanche.
A mixture of water-saturated rock debris that flows downslope under the force of gravity (also called lahar or mudflow).
In volcanology, particles that came out of a volcanic vent, traveled through the air or under water, and fell back on the ground surface or on the ocean floor. [Wikipedia]
A deposit formed by the flowing or intrusion of lava or magma into water, ice, or water-saturated sediment and its consequent granulation or shattering into small angular fragments.
A torrential flow of water-saturated volcanic debris down the slope of a volcano in response to gravity. A type of mudflow.
A flowage of water-saturated earth material possessing a high degree of fluidity during movement. A less-saturated flowing mass is often called a debris flow. A mudflow originating on the flank of a volcano is properly called a lahar.
Volcanic deposits are molten rock (lava), solid rocks and ash which surround a volcano crater. [Wikipedia]