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
December 1, 2025
Dec. 1, 2025 Two decades of satellite and GPS data show the Thwaites Eastern Ice Shelf slowly losing its grip on a crucial stabilizing point as fractures multiply and ice speeds up. Scientists warn this pattern could spread to other vulnerable Antarctic ...
Nov. 30, 2025 New findings show that some coastal regions will become far more acidic than scientists once thought, with upwelling systems pulling deep, CO2-rich waters to the surface and greatly intensifying acidification. Historic coral chemistry and advanced ...
Nov. 28, 2025 Long-term inhalation of toxic air appears to dull the protective power of regular workouts, according to a massive global study spanning more than a decade and over a million adults. While exercise still helps people live longer, its benefits shrink ...
Nov. 27, 2025 Human development and climate-driven sea level rise are accelerating global beach erosion and undermining the natural processes that sustain coastal ecosystems. Studies reveal that urban activity on the sand harms biodiversity in every connected ...
Nov. 27, 2025 Researchers have discovered a low-energy way to recycle Teflon® by using mechanical motion and sodium metal. The process turns the notoriously durable plastic into sodium fluoride that can be reused directly in chemical manufacturing. This creates ...
Nov. 27, 2025 A photosynthetic bacterium shows a surprising ability to absorb persistent PFAS chemicals, offering a glimpse into biological tools that might one day tackle toxic contamination. Researchers are now exploring genetic and synthetic biology approaches ...
Nov. 26, 2025 Beneath the waters off Papua New Guinea lies an extraordinary deep-sea environment where scorching hydrothermal vents and cool methane seeps coexist side by side — a pairing never before seen. This unusual chemistry fuels a vibrant oasis teeming ...
Nov. 26, 2025 Rerouted shipping during Red Sea conflicts accidentally created a massive real-world experiment, letting scientists study how new low-sulfur marine fuels affect cloud formation. The sudden surge of ships around the Cape of Good Hope revealed that ...
Nov. 25, 2025 Researchers studying Yellowstone’s depths discovered that small earthquakes can recharge underground microbial life. The quakes exposed new rock and fluids, creating bursts of chemical energy that microbes can use. Both the water chemistry and the ...
Nov. 24, 2025 Sargassum seaweed is creating major new obstacles for sea turtle hatchlings, drastically slowing their crawl to the ocean and increasing their risk from predators and heat. Despite the physical challenge, their energy stores stay stable, suggesting ...
Nov. 24, 2025 UC Davis researchers engineered wheat that encourages soil bacteria to convert atmospheric nitrogen into plant-usable fertilizer. By boosting a natural compound in the plant, the wheat triggers bacteria to form biofilms that enable nitrogen ...
Nov. 23, 2025 A massive solar storm in May 2024 gave scientists an unprecedented look at how Earth’s protective plasma layer collapses under intense space weather. With the Arase satellite in a perfect observing position, researchers watched the plasmasphere ...
Latest Headlines
updated 12:56 pm ET
Nov. 26, 2025 Scientists decoded DNA from millennia-old lentils preserved in volcanic rock silos on Gran Canaria. The findings show that today’s Canary Island lentils largely descend from varieties brought from ...
Nov. 25, 2025 An immense pocket of hot rock deep beneath the Appalachians may be a wandering relic of the breakup between Greenland and North America 80 million years ago. Researchers suggest this slow-moving ...
Nov. 24, 2025 Using a precisely aligned pair of laser beams, scientists can now hold a single aerosol particle in place and monitor how it charges up. The particle’s glow signals each step in its changing ...
Nov. 23, 2025 About 4.5 billion years ago, a colossal impact between the young Earth and a mysterious planetary body called Theia changed everything—reshaping Earth, forming the Moon, and scattering clues across ...
Nov. 22, 2025 Migratory birds that fill North American forests with spring songs depend on Central America’s Five Great Forests far more than most people realize. New research shows these tropical strongholds ...
Nov. 22, 2025 Scientists discovered that deep earthquake faults can heal far faster than expected, sometimes within hours. Slow slip events in Cascadia reveal repeated fault movements that only make sense if the ...
Nov. 22, 2025 Scientists have uncovered a long-missing piece of the volcanic puzzle: rising magma doesn’t just form explosive gas bubbles when pressure drops—it can do so simply by being sheared and ...
Nov. 21, 2025 Scientists used CRISPR to boost the efficiency and digestibility of a fungus already known for its meatlike qualities. The modified strain grows protein far more quickly and with much less sugar ...
Nov. 20, 2025 Scientists confirmed that West Coast transient killer whales actually form two separate groups split between inner and outer coastal habitats. Inner-coast whales hunt smaller prey in shallow, ...
Nov. 20, 2025 New climate modeling shows that heatwaves will keep getting hotter, longer, and more frequent for centuries—even after the world hits net-zero ...