My experiments with volcanoes

by Thomas Augustus Jaggar

In the first decade of the twentieth century this was new to me as a geologist, for the books did not explain internal gas in lava. Geography understood nothing of the relation of a volcano to lines of cracking earth crust and depth of crust, and gigantic explosions dominated history as exceptions. Refractory slags were then believed to be stiff by reason of chemical fusibility, and gas in solution in a melt is not understood even today. The Japan journey explained the textbook contrast between oceanic Hawaii and continental Ecuador, both volcanic, and the further contrast with Yellowstone agglomerates, and intrusions of the Black Hills of South Dakota. Clearly Hawaii must be studied, and experimental geology extended to the globe as a laboratory.

On my return to Honolulu, Professor Ralph Hosmer, forester, met me and reported that Honolulu money was available, if Massachusetts Tech would send me to Hawaii to found a volcano experiment station. Then and there the Hawaiian Volcano Research Association formed by business leaders in Honolulu became a reality, to crystallize later into an educational corporation.

In 1910, while I was still a professor at Massachusetts Tech, the United Fruit Company invited me to go in one of their ships to study the earthquake destruction of Cartago, Costa Rica. I saw an opportunity to study seismology in the field, as I had studied volcanology in Martinique. The United Fruit Company owned the railroad and much of the national debt of Costa Rica. F. R. Hart, treasurer of M. I. T. and director of the fruit company told me to make my own plans and the company would pay all expenses. Knowing that engineering is of first importance in earthquake disaster, I invited Professor Charles Spofford, head of our Civil Engineering Department, to go with me, and he promptly accepted.

Our journey was from New Orleans, in one of the splendid snow-white steamers of the fruit company. This ship, going by Belize in British Honduras, took us to Limon on the Caribbean side of Costa Rica, a place of banana plantations and Jamaica-negro labor. From Limon we took a mountain-climbing, narrow-gauge railroad, to the high and healthful capital, San Jose. We passed the ruins of the city of Cartago, with its earthquake tumbled churches and wrecked lower buildings, all covered with heavy roofs of red tiles. Don Anastasio Alfaro, government scientist, showed us seismographs and maps, and we called on President Jimenez, who owned a dairy farm on the high slopes of Irazu Volcano directly above Cartago. I arranged with the President to have the government make an official inquiry all over the Republic, suggesting a study of ten grades of earthquake damage, adapted to Central American habits. These grades, from mere alarm up to wrecked churches, were to apply to what had happened in each place. According to the answers, we would make for each place a numerical value of intensity and plot these on the map.

We visited the wreckage of Cartago, where the quake had come like the crack of a whip on May 4, 1910, just at the supper hour. An American railway conductor and his family were seated at table and with the first jarrings, they all pitched forward under the dining room table. When the low adobe house fell on top of them, the table saved their lives. A pathetic object was the hollow square of the Carnegie Palace, designed by a Costa Rican architect to promote Central American peace. It was improperly braced, and everything came down, including the ornate stone wall around the grounds; and a cracked gate post held a melancholy buzzard in the hideous ruin. This and several of the big churches, cracked and disrupted, gave Spofford food for his architectural notes.

The President’s farm on Irazu was a lovely place of green glades, fat cattle, and attractive Spanish dairymaids, at an altitude of more than 9,000 feet. The crater of Irazu at 10,300 feet was a tumbled depression on the top of the mountain with a steaming solfatara on one side, and a lot of circular holes inside, within a rim more or less circular.

Poas crater was very different, with a crater lake of boiling water surrounded by bright-colored horizontal layers of ash. We found buried bombs from a recent eruption which had punctured the soil with holes one or two feet across. There was wild adventure for me in being given a horse at 4 A.M., equipped with a rotten saddle, which slipped when I mounted him. The horse resented me in the early morning darkness, having just left his grain, and immediately bucked off both me and the saddle. More adventure followed. On the ride up the mountain and in the midst of the forest we encountered a jaguar trap which had recently caught two big cats. It was a pen, roofed with logs baited with a fowl, and disguised with brush; a shutter fell and closed the opening when the bait was touched. On the way down we had a terrific tropical thunder storm, with sheets of cold rain, and I got chilled to the bone and was sick with dysentery for two or three days.

There are a dozen volcanoes like these two on the backbone of the Costa Rica rocky mountains. They trend in a ragged line from the Panama boundary on the southeast, to Nicaragua on the northwest. All have records of explosive activity, but lava flows are rare. Beginning at Nicaragua the line of the Cordillera, capped with volcanoes, continues through Salvador, Honduras, and Guatemala; and some of the lower ones have lava flows. Cosequina is famous among them; and conspicuous as a frequently active volcano is Santa Ana in Salvador, one peak of which is Izalco, the index volcano of Central America, erupting frequently. Other index volcanoes are Kilauea for Hawaii, Stromboli for Italy, and Bogoslof for the Aleutians. The next line of volcanoes, also trending northwest, extends from Guatemala into southern Mexico. The Costa Rica line overlaps the northeast side of the Nicaragua-Salvador line, and this in turn overlaps the Guatemala line, and so on. The chains of volcanoes are over an echelon of cracks, surmounted by heaped-up lava peaks on the continental divide.

From the point of view of experimenting with volcanoes, the exploration of the Cartago earthquake and Poas and Irazu craters and a study of their relations typified the unsatisfactory combination of upheaved mountains of strata and of volcanic eruptions and underground friction. This extends all the way along the Cordillera from Patagonia to Alaska. I say unsatisfactory because from the science standpoint, the action of eruption or earthquake is far scattered in time and place, and only local observatory geophysics and traveling scientists will do the work. Cartago is directly at the foot of Irazu Volcano, but the volcano did not erupt simultaneously with the earthquake. In the same way Messina is at the foot of Etna, and Tokyo is at the foot of Fujiyama; and the great earthquakes do not accord with eruptions. Sakurajima in 1914 was an exception, it had a quake after outbreak.

The direct outcome of my study, on the map of Costa Rica, of lines of equal earthquake effects, showed the maximum of the 1910 quake on the continental backbone, and the lines were crowded together along the western mountains. However, they spread out wider and wider along the Caribbean coastal plain, which is an elevated sea bottom on the northeast side of the country. In other words the terrific jolt was a deep slipping or scraping under the volcano line, and the elastic waves of like strong effects were close together in the mountains on the Pacific side, opposed by hard rock. On the other hand these waves, much feebler, widened out their lines in going through flat, soft strata on the Caribbean side. The answer seems to be that along the jagged rupture which underlies the volcanoes there is continuous upward pressure of lava, which occasionally is accelerated into a big bump or slip, now here, now there, as the whole great mountain range volcanically heaves through the ages.