What is Flood basalt?
[[File:3-Devils-grade-Moses-Coulee-Cattle-Feed-Lot-PB110016.JPG|thumb|250px|Multiple flood [[basalt]] flows of the [[Columbia River]] Basalt Group. The photograph shows the step-like character of these formations, called '''traps'''. The upper basalt is the Roza Member, while the lower [[canyon]] exposes Frenchmen Springs Member basalt]] [[File:Parana traps.JPG|thumb|300px|A cliff at the [[Paraná]] Magmatic Province, Brazil. Part of a huge lava flow 128 to 138 million years ago. Parts of this event can be seen in the Etendeka traps in [[Namibia]] and [[Angola]]. These areas were touching in [[Pangaea]]]] A '''flood basalt''' or '''trap basalt''' is the result of a giant [[volcanic eruption]] or series of eruptions that coats large stretches of land or the [[ocean]] floor with [[basalt]] [[lava]]. Flood basalts have covered areas as large as a [[continent]] in [[prehistory]], creating great [[plateau]]s and [[mountain range]]s. Flood basalts have erupted at various times throughout [[Earth history]]. They are clear evidence that the [[Earth]] has periods of higher activity rather than being in a uniform steady state.<ref name=Coffin>Mahoney J.J. & Coffin M.F. Large igneous provinces: continental, oceanic, and planetary flood volcanism. ''Geophysical Monograph'' 100. Washington, DC: American Geophysical Union. [http://myweb.uiowa.edu/dpeate/downloads/Parana-review.pdf.]</ref> One explanation for flood basalts is that they are caused by the combination of [[Rift (geology)|continental rifting]] and its associated [[melting]]. Then a [[mantle plume]] produces vast quantities of a [[basalt]]ic [[magma]]. These have a low [[viscosity]], which is why they 'flood' rather than form taller [[volcano]]es. Flood basalts start at between 100 and 400&nbsp;km depth, in the [[asthenosphere]]. To get a partial [[melting]] as large as that of the traps, expelling huge quantities of lava, it is necessary to have a large [[heat]] input. Such melting can take place near a [[Hotspot (geology)|hotspot]], resulting in a mixture of m