The five major Ice Ages
The Ice Ages episode of In our Time with Melvyn Bragg (14 Feb 2013, 43 mins) discusses many fascinating concepts surrounding Earth’s glacial history and Climate Change. The most striking things to learn may be…
- There have been at least five major Ice Ages (or glaciations) in Earth’s history.
- Earth has been ice-free, even in the high latitudes, for about 85% of its history.
- The first Icehouse Earth occurred at about noon on the 24-hour geologic time scale (about 2.5Ga).
- The last Snowball Earth, where polar ice sheets grow and meet at the equator, occurred about 800Ma and ended with increasing CO2 caused by volcanism.
- The change into an ice age occurs gradually, when more snow falls than melts, rather than a sudden cold snap.
Our current Ice Age
- Our current geologic period, the Cenozoic era or the “Age of Mammals”, began 65Ma with the Cretaceous-Paleogene (K-Pg) extinction event.
- The current ice age, the Quaternary glaciation, beginning about 2.6Ma has featured 40K/100K year cycles of glacials/interglacials.
- The conditions needed to setup the current ice age took about 40M years, beginning with the thermal isolation of the Antarctic.
- The end of the current ice age will occur when the Greenland and Antarctic ice sheets melt. This will happen whether or not humans accelerate it.
Icehouse, Greenhouse, Snowball Earths
- An Icehouse Earth is one in which the global climate makes an ice age possible
- A Greenhouse Earth is one in which tropical temperatures may reach the poles
- A Snowball Earth is one where nearly the entire surface of the Earth is frozen
We gather data on climate change from not only geological strata, ice cores, and the atmosphere, but from the ocean floor, geochemistry, and other surprising chemical and archaeological relations as well as our understanding of the earth’s dynamics and kinematics.
The five major Ice Ages Ice Age Million years ago (Ma) % of Earth’s Age Notes I Huronian 2,400-2,100 50% Configuration of continents highly speculative II Cryogenian 850-635 83.5% Snowball Earth, followed by Cambrian Explosion, first marine animals. III Andean‑Saharan 450-420 90.3% First land plants, continued marine diversification. IV Karoo 360-260 93.1% Land animal diversification, coal bed formation, followed by “Great Dying” (P-Tr) extinction event. V Quaternary 2.5 99.9% Current Ice Age
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