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 9, 2025
Dec. 9, 2025 Scientists discovered a small protein region that determines whether plants reject or welcome nitrogen-fixing bacteria. By tweaking only two amino acids, they converted a defensive receptor into one that supports symbiosis. Early success in barley ...
Dec. 8, 2025 A newly analyzed set of climate data points to a major volcanic eruption that may have played a key role in the Black Death’s arrival. Cooling and crop failures across Europe pushed Italian states to bring in grain from the Black Sea. Those ...
Dec. 7, 2025 A century-old North Atlantic cold patch is now linked to a long-term slowdown in the AMOC, the climate-regulating conveyor belt of ocean water. Only weakened-AMOC models match observed temperature and salinity patterns, overturning recent model ...
Dec. 4, 2025 This year’s ozone hole over Antarctica ranked among the smallest since the early 1990s, reflecting steady progress from decades of global action under the Montreal Protocol. Declining chlorine levels and warmer stratospheric temperatures helped ...
Dec. 2, 2025 As the last Ice Age waned and the Holocene dawned, deep-ocean circulation around Antarctica underwent dramatic shifts that helped release long-stored carbon back into the atmosphere. Deep-sea sediments show that ancient Antarctic waters once trapped ...
Dec. 2, 2025 Dolichospermum, a type of cyanobacteria thriving in Lake Erie’s warming waters, has been identified as the surprising culprit behind the lake’s dangerous saxitoxins—some of the most potent natural neurotoxins known. Using advanced genome ...
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 ...
Latest Headlines
updated 12:56 pm ET
Dec. 7, 2025 A new radiocarbon study has clarified the timing of the colossal Thera eruption, placing it before Egypt’s New Kingdom. Researchers analyzed artifacts tied to Pharaoh Ahmose, gaining rare access to ...
Dec. 6, 2025 Scientists have discovered that complex life began evolving much earlier than traditional models suggested. Using an expanded molecular clock approach, the team showed that crucial cellular features ...
Dec. 4, 2025 Fresh evidence suggests early Earth wasn’t locked under a rigid stagnant lid but was already experiencing intense subduction. Ancient melt inclusions and advanced simulations point to continents ...
Dec. 3, 2025 Researchers recreated conditions from billions of years ago and found that Earth’s young atmosphere could make key molecules linked to life. These sulfur-rich compounds, including certain amino ...
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. 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 ...
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 ...
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. 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 ...
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 ...