Where does all the basalt come from?

…..mid ocean ridges ridges to begin with then it is subducted under the east coast of the North Island

• Most basalt is produced at mid ocean ridges.
• Basalt produced at mid ocean ridges is rafted away as oceanic crust is formed.
• The process of subduction produces mainly basaltic magma
• This basalt is not rafted away from the site of eruption.
• The subducting slab comprises of basalt and gabbro with a thin veneeer of seafloor sediment.
• Water and other fluids move into the overlying “mantle wedge” where they promote partial melting.
• The resulting basalt magma makes its way into the continental crust
• The basalt can end up feeding large volanos such as Mount Ruapehu.
• Broad gently sloping cones such as Auckland’s Rangitoto Island, Lyttleton and Akaroa on the Banks Peninsula.
• In the Auckland region steep sided scoria cones are also formed by the process of fire fountaining.

• Most basalt is produced at mid ocean ridges.
• Basalt produced at mid ocean ridges is rafted away as oceanic crust is formed.
• The process of subduction produces mainly basaltic magma
• This basalt is not rafted away from the site of eruption.
• The subducting slab comprises of basalt and gabbro with a thin veneeer of seafloor sediment.
• Water and other fluids move into the overlying “mantle wedge” where they promote partial melting.
• The resulting basalt magma makes its way into the continental crust
• The basalt can end up feeding large volanos such as Mount Ruapehu.
• Broad gently sloping cones such as Auckland’s Rangitoto Island, Lyttleton and Akaroa on the Banks Peninsula.
• In the Auckland region steep sided scoria cones are also formed by the process of fire fountaining.