A general term for a volcanic vent or pipe drilled through enclosing rocks (usually flat-lying sedimentary rocks) by the explosive energy of gas-charged magmas.
Plugs that bear a particularly strong imprint of explosive eruption of highly gas-charged magma are called diatremes or tuff-breccia.
The diamond-bearing kimberlite pipes of South Africa are diatremes.
Ship Rock, New Mexico:
One of the best known and most spectacular diatremes in the United States is Ship Rock in New Mexico, which towers some 1,700 feet above the more deeply eroded surrounding plains. Volcanic plugs, including diatremes, are found elsewhere in the western United States and also in Germany, South Africa, Tanzania, and Siberia.
-- Excerpts from:
Dictionary of Geological Terms, 1962, and Tilling, 1985, Volcanoes: U.S. Geological Survey Special Interest Publication