Volcano Types | Igneous Rocks

NZ volcanoes

RUNNY LAVA STICKY LAVA

EXPLOSIVE
(pyroclastic)
Mt. Victoria (extinct)

Fire fountain of lava

Low cone, steep sides

E.g. Mt Victoria; Mt Eden

Produces scoria
Mt. Ruapehu (dormant)

Big explosion – ash released

Large volcano – strato

E.g. Mt Ruapehu; Mt Taranaki/Egmont

Produces andesite, ignimbrite, rhyolite, pumice

NON-
EXPLOSIVE
Rangitoto (extinct)

No explosion

Wide cone, not high

E.g. Rangitoto Island

Produces basalt
Table Mountain (extinct)

No explosion – ash released if magma reaches surface

No cone – causes land to bulge

E.g. Table Mountain in Coromandel; Warkworth Dome

Produces granite (plutonic)

	RUNNY LAVA	STICKY LAVA
EXPLOSIVE (pyroclastic)	Fire fountain of lava Low cone, steep sides E.g. Mt Victoria; Mt Eden Produces scoria	Big explosion – ash released Large volcano – strato E.g. Mt Ruapehu; Mt Taranaki/Egmont Produces andesite, ignimbrite, rhyolite, pumice
NON- EXPLOSIVE	No explosion Wide cone, not high E.g. Rangitoto Island Produces basalt	No explosion – ash released if magma reaches surface No cone – causes land to bulge E.g. Table Mountain in Coromandel; Warkworth Dome Produces granite (plutonic)

Rule of thumb
The higher the silica content, the stickier (more viscous) the magma/lava (flows fast if runny and slowly if sticky);
the higher the gas content, the more explosive the eruption (gas escapes due to pressure change at vent causing material to be erupted explosively).

Pictures courtesy of Google Images; based on idea from Rhys Hodson (TGS)

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