Ice age hit Missouri 2.4 million years ago

Analyses of soil from central Missouri have pinpointed just when North America’s most recent spate of ice ages began: 2.4 million years ago.

When the high-energy, extraterrestrial particles known as cosmic rays strike crystals of quartz, they often produce radioactive atoms of beryllium and aluminum. Therefore, the presence of beryllium-10 and aluminum-26 is a sign that the quartz has spent time near Earth’s surface, says Charles W.