Once the signs of glaciation were recognized for the Pleistocene Epoch (roughly 2.6 million to 11,000 years ago), geologists knew how to recognize them in older rocks. Glaciers, geologists realized, could leave giant scratch marks on bedrock and carry boulders to distant landscapes, often dropping those rocks at sea. Soon after the scientific discipline emerged in the early 19th century, geologists began finding clues left by ancient ice bodies.

The evidence for past ice ages comes instead from geology. How do scientists know ancient ice ages happened? Clearly, thermometers weren’t handy when continental-scale glaciers advanced toward the equator. Though relatively warm, interglacials are still part of a glacial epoch. Instead, relatively warm periods intervene, so ice ages are a mix of advancing glaciers (glacials) and retreating glaciers (interglacials). Reading the rock recordĪn ice age is a period of colder-than-usual global temperatures and bigger-than-usual glaciers and ice sheets. CC license by Flickr user SNSF Scientific Image Competition / Francesco Comola. Each year, scientists with the Japanese Antarctic Research Expedition journey from the Antarctic coast to Dome Fuji Station. The coldest place on modern Earth has been identified as a high ridge between Dome Argus and Dome Fuji in East Antarctica. Some of the worst cold struck about 20,000 years ago. Though less severe than the near-global glaciations, the Pleistocene ice ages may have brought the coldest conditions in the last half a billion years.

In the past few million years, glaciers have blanketed huge expanses of the Northern Hemisphere off and on. Although scientists debate exactly how extensive the ice coverage was during these times, the evidence indicates that ice reached sea level in equatorial regions. More deep freezes occurred between 750 and 600 million years ago. Some of the coldest conditions struck over 2 billion years ago, after the rise of atmospheric oxygen. All of these periods have been identified as ancient ice ages. Scientists may never know which period in our planet’s 4.54-billion-year history was the absolute coldest, but research has revealed a few contenders. This article is one of a three-part series on past temperatures, including the hottest the Earth has ever been and how warm the Earth has been “lately.”įor much of its history, our planet has been hotter-sometimes much hotter-than it is today.

The coldest winter ever part 2