11. In 1907, scientists Darton and O'Harra decided that Devils Tower must be an eroded remnant of a laccolith . 12. She carried her investigations to the Ortiz Mountains of New Mexico, which belong to the laccolith type of extinct volcano. 13. It is situated within the Gunnison National Forest and is of a geologic formation called a " laccolith ". 14. After erosion exposed the laccolith , volcanic activity continued and the youngest flows are 1-1.6 million years old. 15. Mashuk is a laccolith with a crystal nucleus, buried under sedimentary rock ( limestone and marl of Upper Cretaceous and Palaeogene ). 16. For instance, Devils Tower in Wyoming was thought to be a volcanic neck, but study has revealed it to be an eroded laccolith . 17. More than of rock which used to exist on top of Square Butte has subsequently eroded to reveal the igneous rock which forms the laccolith . 18. Folds form under varied conditions of compaction or due to the effects of a high-level igneous intrusion e . g . above a laccolith . 19. He coined the term " laccolite " ( now laccolith ) to describe the characteristic shapes of some of the igneous intrusions that core the mountains. 20. In a normal laccolith the intruded material has a flat lower surface and a convex upper surface so that it is more like half a lens in shape.
