He was born in Philadelphia, Pennsylvania in 1871, son of Episcopal Bishop of Southern Ohio Thomas Augustus Jaggar. In 1897, he received his Ph.D. in geology from Harvard University. He spent the next few years as a scientist in the laboratory. He felt strongly that experimentation was the key to understanding earth science. Jaggar constructed water flumes bedded by sand and gravel in order to understand stream erosion and melted rocks in furnaces to study the behavior of magmas. As he matured as a scientist, he began to feel the increasing need for field experimentation. Jaggar wrote at this time,
"Whereas small scale experiments in the laboratory helped me to think about the details of nature...there remained the need to measure nature itself."
Thus Jaggar began a decade-long period of exploration to witness and analyze first-hand natural geologic processes. In 1902, he was one of the scientists that the United States sent to investigate the volcanic disasters at Soufrière and Mont Pelée. With the help of the U.S. Navy and the National Geographic Society, Jaggar landed on the steaming shores of Martinique some 13 days after the disaster. The same year, he was elected a Fellow of the American Academy of Arts and Sciences. In his autobiography published in 1956, Jaggar recounts,
"It was hard to distinguish where the streets had been. Everything was buried under fallen walls of cobblestone and pink plaster and tiles, including 20,000 bodies....As I look back on the Martinique experience I know what a crucial point in my life it was....I realized that the killing of thousands of persons by subterranean machinery totally unknown to geologists...was worthy of a life work."
In 1906 he became head of Massachusetts Institute of Technology's department of geology. The next 10 years of Jaggar's life brought expeditions to the scenes of great earthquakes and eruptions in Italy, the Aleutians, Central America, and Japan. With each trip, Jaggar became increasingly concerned that his field studies were but brief, inadequate snapshots of long-term, dynamic, earth processes. After the 1908 Messina earthquake killed 125,000 people near Mt. Etna in Italy, Jaggar declared that "something must be done" to support systematic, ongoing studies of volcanic and seismic activity. He traveled to Hawaii in 1909 at his own expense, and determined that Kilauea was to be the home of the first American volcano observatory. He would work on that project the rest of his life. He married co-worker Isabel Maydwell in 1917. He moved to Honolulu in 1940 but remained active at the University of Hawaii. He died in Honolulu on January 17, 1953.
After a lecture on his Martinique expedition in Honolulu, Jaggar was approached by Lorrin A. Thurston a prominent Honolulu lawyer and businessman. Thurston, like Jaggar, believed that Kilauea was a prime site for a permanent volcano observatory and inquired of Jaggar, "Is it then a question of money?". Within a year of this conversation, Thurston and other businessmen raised financial backing for the Hawaii Volcano Research Association. A small observing station was set up on the rim of Halemaumau crater. In 1912, support was forthcoming from an MIT alumnus and construction of the new Hawaiian Volcano Observatory began. The first instruments were in a cellar called the Whitney vault adjacent to the Volcano House Hotel. During his early years as Director, Jaggar struggled after private endowments with the hope of eventually securing sponsorship by the Federal Government. In 1919, Jaggar convinced the National Weather Service to fund HVO. The United States Geological Survey took over its operation in 1924, with the exception of a brief hiatus during the Great Depression when HVO was run by the National Park Service. In 1922, volcanologist Thomas Jaggar suggested using Kilauea’s heat for geothermal energy:
“Volcano power for human use is a possibility, for heat is power, and volcanoes generate heat. … Cracks near Halemaumau have opened from time to time which sometimes get hotter and hotter until they become glowing furnaces, emitting apparently merely hot air. If a boring will start such a furnace, then twenty holes at such a place will run a respectable engine.”
On February 3, 1923, when an 8.4-magnitude earthquake hit the southeastern coast of the Kamchatka Peninsula, Jaggar tried to warn the Hilo harbormaster about the possibility that a tsunami could have been generated. At the time of the earthquake, the U.S. had no capability to issue tsunami warnings. Jaggar's warning was not taken seriously and one fisherman was killed when the tsunami hit. Jaggar remained Director of HVO until 1940. The Thomas A. Jaggar Museum in Hawaii Volcanoes National Park is named for him. It was located at the main HVO observatory building until 2018, when eruption-caused structural damage permanently closed the facility.
