Volcanic Dykes and Parasitic Cones
The sides of volcanic cones are often rent during the eruption, and the fissures filled with lava, which hardens and forms rocky ribs called dykes. Sometimes the central cone becomes choked, and secondary or parasitic cones are formed.
Edwin J. Houston, The Elements of Physical Geography, for the use of Schools, Academies, and Colleges. (Philadelphia: Eldredge & Brother, 1891) 25