Blue Mountains Basalts

Blue Mountains Basalts are igneous rocks occurring in the Sydney Basin in eastern Australia.

[3] They have been exposed to a considerable degree of chemical weathering, with a higher iron-oxide concentration than with podzols,[4] hence the reddish colour.

[5] The original volcanic plugs have yet to be discovered, due to the considerable amount of erosion this rock layer has experienced.

Geologists have determined that the Blue Mountains Basalts are derived from a lava flow, not a volcanic plug.

The remnant basalts were formed from a viscous fluid flow of lava, not a vertical inner core of magma as with an eroded volcano.