Late Cenozoic Ice Age

The Late Cenozoic Ice Age, also called the Antarctic Glaciation, started about 34 million years ago at the Eocene-Oligocene Boundary and is still happening. It marks the start of Earth's current ice age or icehouse period. Big ice sheets grew, especially in Antarctica. This was a very important part of this time.

About six million years after it began, the East Antarctic Ice Sheet formed. By 14 million years ago, it was about the size it is today. In the last three million years, glaciers started to spread to the northern parts of the world. This happened when Greenland slowly got covered by an ice sheet during the late Pliocene.

During the Pleistocene Epoch, which began about 2.58 million years ago, the Quaternary glaciation started. This time had colder periods and warmer periods. During the cold glacial periods, huge ice sheets covered much of northern North America and northern Eurasia. This changed the land we see today.

Late Cenozoic Ice Age 33.9 million years ago to present Divisions within the current ice age For divisions prior to 33.9 million years ago, see Geologic time scale
Period	Epoch	Age
↑ Paleogene	Oligocene 33.9 to 23.03 Ma (last epoch of the Paleogene Period)	Rupelian 33.9 to 27.82 Ma
		Chattian 27.82 to 23.03 Ma
Neogene	Miocene 23.03 to 5.333 Ma	Aquitanian 23.03 to 20.44 Ma
		Burdigalian 20.44 to 15.98 Ma
		Langhian 15.98 to 13.82 Ma
		Serravallian 13.82 to 11.63 Ma
		Tortonian 11.63 to 7.246 Ma
		Messinian 7.246 to 5.333 Ma
	Pliocene 5.333 to 2.58 Ma	Zanclean 5.333 to 3.6 Ma
		Piacenzian 3.6 to 2.58 Ma
Quaternary	Pleistocene 2.58 Ma to 11.7 ka	Gelasian 2.58 to 1.8 Ma
		Calabrian 1.8 Ma to 774 ka
		Middle Pleistocene ("Chibanian") ("Ionian") 774 to 129 ka
		Upper/Late Pleistocene ("Tarantian") 129 to 11.7 ka
	Holocene 11.7 ka to present	Greenlandian 11.7 to 8.2 ka
		Northgrippian 8.2 to 4.2 ka
		Meghalayan 4.2 ka to present
The Late Cenozoic Ice Age falls within the Cenozoic Era which started 66 million years ago. The Cenozoic Era is part of the Phanerozoic Eon which started ~538.8 million years ago. In standard nomenclature the Pleistocene Epoch lasts from 2.58 Ma to 11.7 ka and the Holocene epoch lasts from 11.7 ka to present. However, it is disputed whether these should in fact be treated separately, or whether the "Holocene" is in fact merely a Pleistocene interglacial. See below for details.

History of discovery and naming

In 1837, a German scientist named Karl Friedrich Schimper first used the term Eiszeit, which means ice age. At first, this word only described times when glaciers grew. Later, scientists learned that these cold times were part of a much longer ice age.

Today, we know Earth has been in an ice age for about 30 million years. Scientists have used the name "Late Cenozoic Ice Age" since 1973.

The climate before the polar ice caps

The last greenhouse period began 260 million years ago during the late Permian Period. It lasted until 33.9 million years ago. This was a very warm time for Earth. The warmest time was called the Paleocene–Eocene Thermal Maximum. During this time, average global temperatures were around 30 °C (86 °F).

Back then, Australia and South America were connected to Antarctica. In the early Eocene, around 53 million years ago, Antarctica had very mild winters. Trees like palms, beeches, and conifers grew there. As the climate cooled, forests began to shrink and savannas started to appear. Animals also changed and became larger.

Glaciation of the southern hemisphere

Australia moved away from Antarctica, creating the Tasmanian Passage. South America also moved away, forming the Drake Passage. These changes helped make a cold water current called the Antarctic Circumpolar Current. This current circles Antarctica and keeps it very cold.

About 34 million years ago, the climate changed from warm to cooler. This is when Antarctica started to freeze and form large ice sheets. Over millions of years, these ice sheets grew and covered most of the continent. By about 15 million years ago, Earth had a warmer time, but the ice sheets in Antarctica stayed about the same. Later, glaciers also formed in the mountains of the Northern Hemisphere.

Glaciation of the northern hemisphere

The ice in the Arctic of the Northern Hemisphere started to grow about 3 million years ago during the late Pliocene. This happened when Greenland began to freeze over. Around the same time, a land bridge formed between North and South America, which changed ocean currents and made winters colder in the North Atlantic.

Today we are in the Quaternary period, which began 2.58 million years ago. The Quaternary is divided into the Pleistocene, which ended 11,700 years ago, and the current Holocene. During the Quaternary, Earth experienced many cold periods with large ice sheets, called glacial periods, and warm periods with less ice, called interglacial periods. These changes happened because of long-term shifts in Earth’s tilt and orbit, known as Milankovitch cycles.

Last Glacial Period

The Last Glacial Period was a time long ago when big sheets of ice grew and moved into many parts of the north. It started 115,000 years ago and ended 11,700 years ago.

Humans known as Homo sapiens left Africa and moved to new places. They sometimes met other early human groups, like Neanderthals. The Last Glacial Maximum was the coldest time during this period. It happened between 26,500 and 20,000 years ago, when even more land was covered by ice.

Holocene

The Earth is now in a warm time called the Holocene epoch. This is part of a longer ice age. There is less ice now than during the last cold time, but there is still more ice than there was millions of years ago, when only Antarctica had ice sheets. Today, ice covers about 3.1% of Earth's surface and 10.7% of its land area.

Scientists think this warm time might last longer than usual because people have added gases to the air that trap heat. Even so, the climate is expected to get cooler in about 25,000 to 50,000 years. The extra gases might also delay the next cold time by a lot, maybe until 125,000 to 150,000 years from now.

Main article: Holocene climatic optimum