Formation of Basic Igneous

Surface formations

· Obsidean – cools quickly and is glassy

· Scoria – forms when rapid gas escape occurs

· Basalt – 1^st to crystallize

· Pumice – Rapid gas escape gives it a porous appearance and sometimes it can float in water

· Rhyolite – last item to crystallize

Subsurface formations

· Peridotite – 1^st to crystallize

· Diorite – Pressure formed

· Gabbro – Pressure formed

· Granite – Last to crystallize