Volcanoes In The Neighborhood
By Alice Hathaway
Live volcanoes often have craters where rain collects in scalding lakes. When underground heat rises through the water, steam bursts into the sky. As the pressure of gas and hot ejecta builds in the tube, the clouds rise higher. Scientists can guess that an eruption may be imminent by testing the amount of sulfur dioxide in the cloud. Another clue is a foci of earthquakes that close in on the summit. Sometimes a bulge forms near the summit, indicating extreme pressure. There is no sure way of predicting eruptions, but when several signs point to trouble, people are advised to evacuate until the danger passes.
Twenty years ago, my husband, John, and I joined a group of tourists on a trail ride halfway up Colima Volcano. Though dormant, morning mist rolled from its summit. The trail was steep and rocky. Our horses were ready to turn back before we were. I would not venture that close today, but more daring climbers will go to the top.
When the late Neill James joined a Mexican Explorers’ Club climb into Popocatepetl seventy years ago, that volcano was active, but not quite as dangerously close to eruption as it is today. The party spent two bitterly cold nights and a day within the rim. One by one they climbed down a 225-foot rope ladder over rotten ice walls into the lower crater. She describes the experience in Dust On My Heart, a book she wrote in Ajijic during the 1940s.
“It was like walking about in the throat of a giant. Sulfur fumes and steam hissed from cracks in the lava all about us, and rose from the bottomless lake. It was like a preview of Christianity’s much-publicized Hell. Sulfur fumes smelled like rotten eggs. We fashioned gas masks from bandannas. Many men suffered violent headaches. We made a circuit of the walls of the crater, and then climbed gingerly down to the shore of the lake. Large boulders, weighing tons, tossed up by an eruption, were precariously balanced upon the steep slopes. There was always danger of setting one in motion and liquidating members of the party on a lower level. The blue-green, bubbling lake surrounded by large, smooth volcanic boulders lacked only palm trees to form a bit of Paradise in Hell.
But it was far too hot for swimming. I thought to bathe my feet, which had been encased in heavy boots for thirty-six hours, but could not sustain even a toe in the hot water. We circled the lake, and walked about the bottom of the crater peering into sulfur vents, breathing-holes for the immense power trembling beneath our feet.”
From the terrace of our home in Ajijic, I look south across Lake Chapala at cone-shaped Mount Garcia. It’s one of many extinct volcanoes that rose eons ago. The dome on top may be a hardened lava stopper that sealed the tube and ended an eruption. Lower down the slope is another cone, perhaps a later eruption that broke through rubble under the cork. Beyond Garcia, mountain ridges line the horizon.
Popocatepetl, Colima and Garcia are part of a chain of mountains, rivers and lakes across the width of Mexico. Oceanic crust, more dense than continental crust, “subducts” beneath the latter, causing earthquakes and volcanoes where the land is thrust up by the tremendous force of moving plates. Geologists have identified the relatively minor Cocos plate moving north under Mexico, causing a jagged rift. As described in Many Mexicos, by Lesley Byrd Simpson, “That rift, or tectonic seam, extends from Cape Corrientes on the Pacific coast, eastward to Tuxtla San Andres in Vera Cruz, on the Gulf of Mexico. North and south of the seam, huge blocks were up-tilted into what we call the Central Plateau which covers about two thirds of the total area of the country. The seam itself is a chaotic belt of broken land 100 miles wide and 800 miles long. Through -it a magnificent procession of volcanoes pushed up: Colima, Sanganguey, and Ceboruco, at the Pacific end; the Nevado de Toluca, Ajusco, Popocatepetl, Ixtaccihuati, and Malinche, on the Plateau; and the incomparably beautiful Pico de Orizaba, whose dazzling snow-capped cone rises more than 18,000 feet and may be seen from a hundred miles out in the Gulf of Mexico.”
The upheaval did not happen all at once; indeed it is still going on today. Occasional earthquakes and volcanic activity remind us of the restlessness of Mother Earth. We who live with her and love her must learn to understand and respect the pressures she bears.