Question: Given the following context:  Harry Glicken (March 7, 1958 – June 3, 1991) was an American volcanologist. He researched Mount St. Helens in the United States before and after its 1980 eruption, and was very distraught about the death of fellow volcanologist David A. Johnston, who had switched shifts with Glicken so that the latter could attend an interview. In 1991, while conducting avalanche research on Mount Unzen in Japan, Glicken and fellow volcanologists Katia and Maurice Krafft were killed by a pyroclastic flow. His remains were found four days later, and were cremated in accordance with his parents' request. Glicken and Johnston remain the only American volcanologists known to have died in volcanic eruptions. Despite a long-term interest in working for the United States Geological Survey, Glicken never received a permanent post there because employees found him eccentric. Conducting independent research from sponsorships granted by the National Science Foundation and other organizations, Glicken accrued expertise in the field of volcanic debris avalanches. He also wrote several major publications on the topic, including his doctoral dissertation based on his research at St. Helens titled "Rockslide-debris Avalanche of May 18, 1980, Mount St. Helens Volcano, Washington" that initiated widespread interest in the phenomenon. Since being published posthumously by Glicken's colleagues in 1996, the report has been acknowledged by many other publications on debris avalanches. Following his death, Glicken was praised by associates for his love of volcanoes and commitment to his field.  answer the following question:  What is the last name of the person whose research at St. Helens formed the basis for his doctoral dissertation?
Answer:
Glicken