Volcaniclastics

Volcaniclastics are a type of sedimentary rock that are formed from the accumulation and lithification of volcanic material, such as ash, lapilli, volcanic bombs, and other tephra. They are a significant component of the geologic record, providing important information about past volcanic activity and the earth's history.

Formation

Volcaniclastics form when volcanic material is ejected during an eruption, transported by wind or water, and then deposited. The material can be deposited in a variety of environments, including on land, in the ocean, or in a lake. The deposited material is then buried and lithified, or turned into rock, through the processes of compaction and cementation.

Classification

Volcaniclastics are classified based on the size of the volcanic material they contain. Ash-size particles form ashstone, lapilli-size particles form lapillistone, and larger particles form volcanic breccia or volcanic agglomerate. The composition of the volcanic material can also be used to classify volcaniclastics, with terms such as basaltic, andesitic, and rhyolitic used to describe the type of volcanic rock from which the material originated.

Importance

Volcaniclastics are important for several reasons. They provide a record of past volcanic activity, including the type of eruption, the volume of material ejected, and the distance the material was transported. They can also provide information about the environment in which they were deposited, such as whether it was terrestrial or marine. In addition, volcaniclastics can be a source of valuable minerals, such as gold, silver, and copper.

See also

• Sedimentary rock
• Volcanic rock
• Tephra
• Volcanic eruption