Show science seeks clue to misplaced vein of volcanic lava laifa BOULDER DAM COLO ten miles south of this massive concrete structure geologists have discovered a missing link in volcanic history a lava lama dike formed in gravel how it got there is the problem worrying prof lan ian campbell of the california institute of technology and dr E T schenk of the national park service who have decided the dike is a mere geological youngster of some years never before has lava been found cutting through gravel and how it forced its way into q a porous rock of this type in such clean cut fashion is a big mystery A possible explanation may be that the first surge of lava was rapidly chilled by contact with the cold and perhaps water filled gravel this chilled glass thenceforward formed a seal which prevented any side escape as the remaining bulk of the magma pushed in I 1 Spec spectacular tac ular too is the texture of the dike itself most dikes that are intruded into the shallower parts of the earths crust are very fine grained |