#Living earth price sheet free#

Eventually there will be more and more snow building up, and that will pack down into a glacier. If the summers are cool enough, the snow lasts until the next winter. And of course, less energy from the sun means colder temperatures.ĭuring the colder winters, snow falls on the land. “Even though the tilt changes by only one degree or two, that’s enough to change the angle at which the sun's energy hits,” explains Elizabeth Thomas, a paleoclimatologist at the University at Buffalo.

These very minor (and regular) adjustments in the angle of the Earth relative to the sun affects the amount of solar radiation, or insolation, that reaches Earth. Over time, the tilt of the Earth, its orbit, and its wobble change a bit. But there are some variations in the pattern. What Causes Ice Ages?Įarth goes about its business in a pretty regular way, spinning on its axis and looping around and around the sun. That’s why we have ice caps at the poles while temperatures are more or less comfortable (for humans) on most of the planet. We’re in an interglacial now - this one began around 10,000 years ago. (By contrast, the periods of time when glaciers advance are called, fittingly, glacials.) Interglacials can last tens of thousands of years.

#Living earth price sheet free#

Within these major ice ages there are warmer, shorter-term periods, called interglacials, when the ice sheets retreat, and some, or even most, of the planet is free of ice. That’s hard to believe in these days of dangerously increasing global temperatures, but ice ages aren’t uniformly hard-frozen.

That’s right, we’re living in an Ice Age. The last one began about 2.5 to 3 million years ago. There have been five major ice ages in Earth’s 4.5-billion-year history. Periodically, global temperatures drop, ice sheets form at the poles, then the ice creeps down to cover the continents.