Editing Tuff (section)

===Mafic volcanism===
[[File:Diamond Head Hawaii From Round Top Rd.JPG|thumb|Diamond Head, a tuff cone]]
[[File:Moai Rano raraku.jpg|thumb|upright|Most of the [[moai]]s in [[Easter Island]] are carved out of [[tholeiite]] basalt tuff.]]

Mafic volcanism typically takes the form of [[Hawaiian eruption]]s that are nonexplosive and produce little ash.<ref>{{cite book |last1=Macdonald |first1=Gordon A. |title=Volcanoes in the sea: the geology of Hawaii |date=1983 |publisher=University of Hawaii Press |location=Honolulu |isbn=0-8248-0832-0 |page=9 |edition=2nd}}</ref> However, interaction between basaltic magma and groundwater or sea water results in hydromagmatic explosions that produce abundant ash. These deposit ash cones that subsequently can become cemented into tuff cones. [[Diamond Head, Hawaii]], is an example of a tuff cone, as is the island of [[Ka'ula]]. The glassy basaltic ash produced in such eruptions rapidly alters to [[palagonite]] as part of the process of lithification.{{sfn|Macdonald|1983|pp=17-20}} 

Although conventional mafic volcanism produce little ash, such ash as is formed may accumulate locally as significant deposits. An example is the Pahala ash of [[Hawaii (island)| Hawaii]] island, which locally is as thick as {{convert|15|meters|feet|sp=us}}. These deposits also rapidly alter to palagonite, and eventually weather to [[laterite]].{{sfn|Macdonald|1983|pp=349-353}} 

Basaltic tuffs are also found in [[County Antrim]], [[Isle of Skye|Skye]], [[Isle of Mull|Mull]], and other places, where [[Paleogene]] volcanic rocks are found; in Scotland, [[Derbyshire]], and Ireland among the [[Carboniferous]] strata, and among the still older rocks of the Lake District, the southern uplands of Scotland, and Wales. They are black, dark green, or red in colour; vary greatly in coarseness, some being full of round spongy bombs a foot or more in diameter; and being often submarine, may contain shale, sandstone, grit, and other sedimentary material, and are occasionally fossiliferous. Recent basaltic tuffs are found in [[Iceland]], the [[Faroe Islands]], [[Jan Mayen]], Sicily, the [[Hawaiian Islands]], [[Samoa]], etc. When weathered, they are filled with calcite, chlorite, [[Serpentine group|serpentine]], and especially where the lavas contain [[nepheline]] or [[leucite]], are often rich in [[zeolite]]s, such as [[analcite]], [[prehnite]], [[natrolite]], [[scolecite]], [[chabazite]], [[heulandite]], etc.<ref name=EB1911/>