1. These typically small surface volcanic craters extend downward in formations known as volcanic pipes . 2. The volcanic pipe is a diatreme, composed of olivine lamproite, present as tuff and lava. 3. The "'Mountain Lake cluster "'consists of two diatremes or volcanic pipes in Northern Alberta, Canada. 4. The area of North Bay contains a number of ancient volcanic pipes , including the Bonfield ). 5. The youngest rocks are diatremes, referring to breccia-filled volcanic pipes that were formed by gaseous explosions. 6. The 35-acre Crater of Diamonds State Park is the eroded surface of an ancient gem-bearing volcanic pipe . 7. Diamond-bearing volcanic pipes are closely related to the oldest, coolest regions of continental crust ( cratons ). 8. At Carrickarede, the ancient volcanic pipe has left dolerite, a tougher rock than basalt, which erodes more slowly. 9. This metamorphic succession is penetrated by six early Pliocene, rhyolitic volcanic pipes , with rare occurrences of small obsidian. 10. These volcanic pipes are genetically associated with the rhyolitic, pyroclastic rocks that cover the whole southern part of Antiparos.
