The geological period when the earth's surface is covered by large-scale glaciers is also called the ice age. The only relatively warm period between two glacial periods is called interglacial period. There have been many ice ages in the history of the earth, and the latest one is the Quaternary Ice Age.

In the history of the earth's development, the ice age only accounts for about 10% of the whole earth's historical period, and most of the time it is in the warm period. The main ice ages that have been confirmed are as follows.

Neoarchean Great Ice Age

This is the earliest known Great Ice Age on earth. The moraine of Gao Qian Formation of Huron Group in the Great Lakes region of southern Canada and the western United States is represented by 2.7-2.35 billion years ago. In addition, there are products of this ice age in South Africa, Western Australia and India. The Great Ice Age lasted about 40 million years.

Precambrian glacial period

About 9.5 ~ 6.65438+0.5 million years ago, it was a great ice age with wide influence. Its remains have been preserved in many parts of the world except the Antarctic continent, and most of them are separated by non-glacial sedimentary rocks, indicating that the ice age was multi-stage. It was first discovered in Scotland and Norway, and then in China, Australia, Africa, Greenland and North America. It is represented by moraine in Finnmark, northern Norway. Nantuo moraine with scratches at the bottom of Sinian system in China is mainly distributed in the middle and lower reaches of the Yangtze River.

Early Paleozoic Great Ice Age

It happened during the Great Ice Age from Late Ordovician to Early Silurian. About 460 ~ 440 million years ago, some people thought it might last until the late Devonian (360 million years ago). Its mixed rocks are distributed in France, Spain, Canada, South America, North Africa and the new islands of the Soviet Union. The moraine outcrops in North Africa are excellent, and some remains of glacial landforms have been preserved, such as well-preserved glacial structures, raised mounds, serpentine mounds and sand wedges.

Late Paleozoic Great Ice Age

Ice age from Middle Carboniferous to Early Permian. At that time, the global temperature generally dropped, forming a large area of ice sheets and glaciers, which lasted for 80 million years and was the most far-reaching major ice age in the history of the earth. Found in India, Australia, South America, Africa and the edge of Antarctic continent. Southeast Australia and Tasmania were the areas with the strongest glaciation during the Great Ice Age.

Late Cenozoic Great Ice Age

This is the latest major ice age in the history of the earth. Since the Neogene, there has been an alternation of glacial and interglacial periods, which has continued to this day. As early as Oligocene, the Antarctic ice sheet began to appear. In the middle Miocene, the ice sheet had reached a certain scale, and it was the first area to enter the ice age. Glacier environment in the early Quaternary spread all over the world, reaching its peak in the middle period, so the Late Cenozoic Great Ice Age mainly refers to the Quaternary Ice Age. At that time, there were two ice sheets in the northern hemisphere, Scandinavian ice sheet and Lauren ice sheet in North America. The southern boundary of the former reaches 50 north latitude, while the latter reaches about 38 north latitude. In addition, in some high mountain areas in the middle and low latitudes, foothill glaciers or small ice caps have developed. About 8000 ~ 10000 years ago, global warming, a large number of glaciers and ice sheets disappeared or contracted, and the earth entered the post-glacial period. However, the glaciers and ice sheets on the mainland have not completely disappeared.

Quaternary glaciation

Quaternary glacial periods are divided as follows:

The division of the world. 190 1~ 1909 German A. Punk and E. brukner publishing houses successively published Alps in the Ice Age (3 volumes). According to the development of several gravel terraces in the upper reaches of the Danube River at the northern foot of the European Alps, it is proposed that there were four glacial periods and three interglacial periods in this mountainous area, which were named as Junz and Junz respectively from the old to the new. Later, B. Abel and I. Schaefer supplemented the older Danube Ice Age and the older Bieber Ice Age. For decades, alpine ice age system has been widely spread and adopted in many parts of the world, and compared with other parts of the world as a typical ice age model.

In the 1920s, some scholars divided the final moraine series of Denmark, the Netherlands, northern Germany and Poland into four glacial periods and three interglacial periods according to the active position of the Nordic Scandinavian ice sheet edge. From the old to the new, the glacial periods were elster, Sal, Watt, Vizer, cromer and Holstein. The ice age series in North America is mainly determined according to the Nordic ice age division method. According to the position of moraine and moraine, there are four glacial periods in Wisconsin, Illinois, Kansas and Nebraska, and three interglacial periods in Sangamon, Amos and Afton. Some other parts of the world have also divided the Quaternary glacier series in this area. Later, the solar radiation curve established by M. Milankovic since one million years ago shows that at least 14~ 15 glacial cycles can be divided, that is, almost every glacial cycle in the alpine glacial series contains 2~3 glacial cycles. The study of oxygen isotope in deep-sea cores developed in 1950s has impacted the traditional alpine glacier system, because it can't completely record the information of climate and environmental changes, and the related strata and landforms are easily misinterpreted. However, the isotope of deep-sea core can record the most accurate Pleistocene climate and environmental change data so far, almost unaffected by the geographical location of the core, and its continuity and universality are the only ones in the world that can be verified by comparing with the reliable data of other climate stratigraphic systems. According to the records of 18O in the deep sea core of the Pacific Ocean, there are 23 complete ice ages of 18O and 10 (from stage B to stage K) since about 900,000 years, and the boundary between each period is 1 1 (from I to VII) It can be compared with the alpine ice age system in time series.

Loess is a necessary layer of Pleistocene, which is widely distributed on land. It has developed since the Quaternary, and has been almost continuously deposited to this day. Because of the preservation of complete loess-paleosol sedimentary sequence, biological fossils and climate information, it is the most ideal object to study the Quaternary environmental changes in Chinese mainland, and can also be compared with deep-sea sediments. Loess is mostly deposited in glacial period, mostly distributed in the periphery of ancient ice sheets in Europe and North America. During the interglacial period when the ice sheet retreated, the climate was humid and brown soil developed, forming an alternate sedimentary profile of loess and brown soil, which recorded the climate cycle from the glacial period to the interglacial period. The sedimentary sequence of brown soil in European loess forest can be divided into several sedimentary cycles and sub-cycles, which can correspond to the Nordic Ice Age series. Loess is widely distributed in China, and its thickness can reach 4 10 meter. Nowadays, the study of Luochuan section in Shaanxi shows that the 1 1 paleoclimate group has been recorded since about 2.4 million years ago, which can be compared with the European loess sedimentary cycle series. Among them, the loess sequence 900,000 years ago has a good correspondence with marine facies 18O period 1~23.

(2) China's split and performance. The ice age division of the mountains in western China has been recognized by people. Taking the well-studied northern slope of Mount Qomolangma in Himalayas as an example, the Quaternary Glacial Period can be divided into: a. The Himalayan Glacial Period based on the old moraine platform near the northern slope of the early Pleistocene Xixiabangma Peak. B The Middle Pleistocene Niexiongla Ice Age was established according to the ice water-moraine deposits in the Niexiongla Plateau on the west side of Mount Everest. C. The broken boulder near Keelung Temple in Rongbu Valley and the terminal moraine of Rongbu Temple in the upstream represent the Keelung Temple stage in the early late Pleistocene and the Rongbu Temple stage in the late late Pleistocene respectively, which constitutes the Qomolangma Ice Age in the late Pleistocene. Some scholars have also divided these two stages into two independent ice ages.

The Quaternary Ice Age in eastern China is still controversial. 1944, taking Lushan Mountain as a model, Li Siguang divided the Quaternary glaciers in eastern China into Poyang, Dagu and Lushan glaciers from old to new, and added Dali Glacier, the last glacier proposed by H.von Fei Shimeng in 1937, to establish the Quaternary Glacier Series in eastern China. In this regard, some Chinese and foreign scholars have always held different opinions. In the early 1980s, Shi Yafeng and others suggested that there were Quaternary glacial remains in mountainous areas above 3,500 meters above sea level, such as Taibai Mountain, the main peak area of Changbai Mountain and the central mountains of Taiwan Province Province, but there was no reliable evidence of ancient glaciers in the middle and lower reaches of the Yangtze River, Guilin, Guangxi, Shennongjia, Hubei, Xishan in Beijing and Daxinganling in Northeast China. The eastern and western parts of China showed different forms during the Quaternary Ice Age. The eastern part does not have the water, heat and terrain conditions to develop into a mountain glacier, but it is in a relatively cold climate. The ancient glacial remains in the east confirmed by Li Siguang are not caused by glaciers, for example, the debris flow accumulation is mistaken for moraine. There is no basis for the Quaternary glacial sequence in eastern China except Dali glacial.

Five ice ages

About 2.4 billion to 2,654.38 billion years ago-the Huron Ice Age.

About 850 million to 635 million years ago-the ice age

About 450 million to 420 million years ago-Ordovician

About 360 million to 260 million years ago-Carboniferous period

About 2.58 million years ago-Quaternary Ice Age