Reference Terms
from Wikipedia, the free encyclopedia
Ice age
An ice age is a period of long-term reduction in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers. Glaciologically, ice age is often used to mean a period of ice sheets in the northern and southern hemispheres; by this definition we are still in an ice age (because the Greenland and Antarctic ice sheets still exist). More colloquially, when speaking of the last few million years, ice age is used to refer to colder periods with extensive ice sheets over the North American and Eurasian continents: in this sense, the most recent ice age ended about 10,000 years ago.
There are three main types of evidence for ice ages: geological, chemical, and paleontological. Geological evidence for ice ages comes in various forms, including rock scouring and scratching, glacial moraines, drumlins, valley cutting, and the deposition of till or tillites and glacial erratics. Successive glaciations tend to distort and erase the geological evidence, making it difficult to interpret. It took some time for the current theory to be worked out.
There have been at least four major ice ages in the Earth's past. Outside these periods, the Earth seems to have been ice-free even in high latitudes.
Related Stories
1
2
Earth & Climate News
October 21, 2026
Oct. 21, 2026 Scientists have cracked a 178-year-old mystery surrounding a train delayed by a solar storm, revealing that the famous incident happened in 1848 rather than 1841. The discovery rewrites the early history of space weather and highlights a threat that ...
Oct. 20, 2026 A new study reveals that improved hurricane forecast graphics may help people identify threatened areas without making them more likely to recognize the danger or take protective action. Researchers also found that a widespread misunderstanding of ...
Oct. 19, 2026 A massive landslide in Alaska triggered the second-highest tsunami ever recorded, sending water and debris 1,580 feet up a mountainside just hours after tourists visited the area. Scientists discovered that the disaster was preceded by several ...
Oct. 19, 2026 Scientists have discovered evidence of two hidden magma sources beneath Nicaragua’s Masaya volcano, where satellite observations revealed mysterious ground movements suggesting magma is shifting deep underground. The findings could improve ...
Oct. 19, 2026 Scientists have discovered that severely bleached corals can make a remarkable comeback simply by touching healthy, genetically identical corals. In laboratory experiments, dying corals regained their color and fully recovered within seven weeks, ...
Oct. 18, 2026 A catastrophic volcanic eruption 7,300 years ago devastated Japan, but new research reveals that its impact on prehistoric populations was far more complex than previously believed. While some ...
Oct. 17, 2026 El Niño is fueling a dangerous cascade of wildfires across the tropics, with the Amazon rainforest now experiencing widespread burning and scientists warning that the worst may still be ahead. NASA researchers are uncovering dozens of previously ...
Oct. 17, 2026 Scientists have discovered that some forest soils are becoming surprisingly better at removing methane from the atmosphere as temperatures rise and rainfall declines. A study spanning up to 24 years found methane absorption increasing by an average ...
Oct. 16, 2026 Scientists have discovered a remarkable “Pac-Man enzyme” that helps bacteria devour certain types of plastic and may offer new hope in the fight against plastic pollution. Researchers found that ...
Oct. 15, 2026 Antarctic sea ice reached its third-lowest winter maximum in 2026, extending a remarkable decline that began after years of record-breaking growth. Scientists are investigating whether the dramatic reversal signals a long-term shift in Antarctica's ...
Oct. 15, 2026 Arctic sea ice is shrinking in both winter and summer, with satellite records revealing that the region's remaining ice is becoming thinner, younger, and more vulnerable to melting. Despite a recent slowdown in summer losses, scientists warn that ...
Oct. 15, 2026 Scientists have discovered a potential new weapon against a devastating fungus that threatens rice, wheat, and barley worldwide. By engineering a special type of plant immune receptor, researchers ...
Latest Headlines
updated 12:56 pm ET
Oct. 21, 2026 A decades-long mystery beneath the North Sea has finally been solved. Scientists have confirmed that the Silverpit Crater, buried 700 meters below ...
Oct. 16, 2026 As Hurricane Simon unleashed destructive winds and flooding along Mexico’s coast, NASA satellites captured an extraordinary sight: massive atmospheric waves rippling high above the storm. The rare ...
Oct. 12, 2026 Europe's Sentinel-3C satellite has returned breathtaking images of Earth just two weeks after launch, revealing the snowy Alps, frozen Arctic ...
Oct. 12, 2026 Scientists may have solved a 2.3-billion-year-old mystery about how Earth maintained enough oxygen to support life. Ancient rocks reveal that ...
Oct. 12, 2026 Australia's normally dry, rust-colored outback has erupted into a spectacular carpet of wildflowers after unusually heavy rains, potentially producing its most impressive bloom in nearly 20 years. ...
Oct. 11, 2026 An astronaut aboard the International Space Station photographed a remarkable formation in Madagascar that looks surprisingly similar to the Moon’s bright highlands. Made of anorthosite, a rock ...
Oct. 8, 2026 A brilliant yellow coral discovered off Costa Rica proved so unusual that scientists had to create an entirely new family to classify it. The meter-tall colonies rise from seafloors covered in ...
Oct. 7, 2026 Earth’s center of mass is constantly on the move, shifting by a few millimeters as enormous amounts of water, ice, and even air migrate around the planet with the seasons. NASA scientists have ...
Oct. 6, 2026 New research suggests animals could have evolved as early as 800 to 700 million years ago, roughly 200 million years earlier than some previous estimates. If so, the first animals may have lived ...
Oct. 4, 2026 A meteor crater buried beneath Oklahoma has turned out to be nearly 100 million years younger than scientists thought. Zircon crystals show the Ames impact occurred about 370 million years ago, ...