Alaska, Volcanic Eruption

- Andesitic lava is typically formed at convergent boundary margins of tectonic plates, by several processes:
+ Hydration melting of peridotite and fractional crystallization
+ Melting of subducted slab containing sediments
+ Magma mixing between felsic rhyolitic and mafic basaltic magmas in an intermediate reservoir prior to emplacement or lava flow.