Interglaciation: Definition & Explanation on the Interglacial Period

Instructor: Christopher Sailus

Chris has an M.A. in history and taught university and high school history.

In this lesson, we'll explore the term interglaciation. Throughout this process, we'll discover exactly what determines a glacial period and the way in which these fluctuations in Earth's climate have changed history.

Long Seasons

Every few years, we are just lucky enough to have summer last a few extra months. You and your friends likely take advantage of the so-called 'Indian Summer' with a few extra cookouts, a few more days in the pool, perhaps even an October weekend at the beach - taking full advantage of the extra sun before autumn and winter fully take hold.

What many people don't realize, is that the Earth goes through long periods of warming and cooling similar to our seasons as well, called glacial and interglacial periods.

What Exactly Is Interglaciation?

Interglaciation is the term used by geologists to refer to the alternating periods of warming and cooling in the Earth's past. In cooler times, termed 'glacial periods,' the glaciers and ice shelves from the arctic slowly creep southward and spread across the Earth; for example, at the height of the last glacial period (about 18,000 years ago), glaciers covered North America as far south as the Ohio River! However, in between these periods the Earth is far warmer, causing the glaciers to melt and recede northward. These are referred to as 'interglacial periods.' We are currently in an interglacial period, since approximately 12,500 years ago. Though the period itself is currently unnamed, most geologists refer to the time period from 12,500 years ago up to present day as the Holocene epoch. To better understand interglaciation, let's examine a rough timeline of Earth's ice ages and our current one.

Quaternary Period

Researchers have categorized Earth's glacial history into five major ice ages. The four ice ages of the past were the Huronian, Cryogenian, Andean-Saharan, Karoo, while our current ice age is called the Quaternary period. Yes, despite what it might feel like in August, we are actually in the middle of one of Earth's five major ice ages! The Quaternary stretches from the present day back to 2.5 million years ago. Geologists have further sub-categorized the Quaternary ice age in order to better define the glacial and interglacial periods. Throughout the Quaternary period, the Earth has experienced several fluctuations between glacial and interglacial periods, generally lasting about 40,000-100,000 years each. As mentioned earlier, our most recent interglacial period began roughly 12,500 years ago, and it is believed the warming Earth associated with it helped to create the conditions which allowed for humans to begin basic agricultural practices and more sedentary lifestyles. Scientists and researchers have given names to a few of the interglacial periods preceding our current period.

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