Hazards

The Yellowstone Plateau in the northern Rocky Mountains in Wyoming, Montana, and Idaho is centered on a youthful, active volcanic system with subterranean magma (molten rock), boiling, pressurized waters, and a variety of active faults with significant earthquake hazard.

From 1,500 to 2,500 earthquakes typically occur each year within Yellowstone National Park and its immediate surroundings.

Yellowstone's volcanic and hydrothermal history suggests the potential for various kinds of eruptions in the future.

The most likely type of volcanic eruption at Yellowstone would produce lava flows of either rhyolite or basalt.

Ash and tephra fall are the most widespread volcanic hazard. Even lava-flow eruptions could include explosive phases that might produce significant volumes of volcanic ash and pumice. The least-likely scenario is another caldera-forming eruption, in which case much of the United States, southern Canada, and northern Mexico would experience some ashfall.

Although very unlikely to occur, a caldera forming eruption would produce massive pyroclastic flows.

If another catastrophic caldera-forming Yellowstone eruption were to occur, it quite likely would alter global weather patterns and have enormous effects on human activity, especially agricultural production, for one-to-two decades.