11. This has a number of weirdly shaped rock pinnacles, the remains of ancient volcanic plugs . 12. The hill is the fifth in a series of volcanic plugs called the Nine Sisters. 13. Trindade is a mountainous, desiccated volcanic island with numerous phonolitic lava domes and steep-sided volcanic plugs . 14. Mount PMhaturoa ( 520 m ) is a distinctive volcanic plug that dominates the Atiamuri landscape. 15. They are geologically noteworthy for being volcanic plugs . 16. "This feature is an eroded volcanic plug -the most distinctive navigational landmark on the entire North Beach. 17. Another building on a volcanic plug is the 14th century Trosky Castle in the Czech Republic. 18. The volcanic plug rises about above the surroundings. 19. "' Castle Rock "'is a volcanic plug in the middle of Edinburgh upon which Edinburgh Castle sits. 20. Erosion has revealed a volcanic plug on the western peak, giving the hill its distinct breast-like shape.
