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