The Mystery of the Cataclysm

Some million years ago as the Basin and Range Province took shape, a long, violent series of volcanic eruptions shaped the face of the Big Bend area and much of the rest of the Chihuahuan Desert. This period of intense volcanic activity shaped much of the American Southwest. In some places, great bubbles of molten rock pushed toward the surface, remelting rocks and causing great domes, bows, and folds. In many places, the superheated, pressurized rock broke through to the surface, creating volcanoes, lava flows, and outbursts of ash that sometimes smothered large areas. This period of volcanic activity left many of the distinctive landforms of the Southwest, including badlands covered with jagged lava and volcanic plugs, monoliths of once-molten rock that hardened in the throat of a volcano. These volcanic plugs now loom over an eroded landscape of softer rock.

For a long time, geologists believed that the Earth was patient and steady in its shifts and that change took place at a steady pace. Increasingly, however, geologists have come to recognize that the deep currents in the Earth’s semi-molten mantle must undergo great changes or cycles that sometimes cause a global increase in volcanic activity. These periods of increased volcanic activity may account for dramatic transformations in Earth’s surface like the breakup of the Pangea supercontinent, climatic shifts, and the shape of the North American Southwest and its deserts. For whatever reason, the major volcanic activity in the Chihuahuan largely ended about 5 million years ago. Since then, erosion has dominated throughout the region as time, ice, and water set to work leveling both the Rocky Mountains and the Sierra Madre.