Over the past 2.7 billion years, the Earth has experienced five major ice ages and four major warm periods. Why is this the case? The reasons are not entirely clear. Some scholars believe that this is related to the Earth's orbit. When the Earth is closer to the sun, it receives more solar energy, so the climate is warmer; while when the Earth is far from the sun, it receives less solar energy, and the climate becomes colder. Some scholars believe that this is related to major crustal movements on Earth. Crustal movements create high mountains, where the air is thin and there is less dust and water vapor, making it easier for heat to dissipate and causing the surface to cool. At the same time, crustal movements also expand the land area and cause sea retreat. The heat capacity of land is much smaller than that of seawater. With the expansion of land and the reduction of ocean area, less energy is stored on the surface, and the surface temperature easily drops to become extremely cold. Several major ice ages in geological history are related to periods of active geological structures... However, these theories have not been widely accepted. The Quaternary glacial period, in which the Earth currently resides, can be further divided into seven cooler glacial periods and seven warmer interglacial periods. With the advancement of technology and the improvement of testing methods, the geological history of the past 700,000 years can be divided into seven minor glacial periods and seven interglacial periods, with glacial and interglacial periods alternating roughly every 100,000 years. Energy from the sun and the Earth's interior causes many natural phenomena on land, at sea, and in the atmosphere. These natural phenomena have a significant impact on climate change.
The most recent minor glacial period occurred 18,000 years ago. At that time, the summer water temperature was 2.3℃ lower than it is today, so after the water evaporated, most of it turned into snow and was frozen in North America, Eurasia, the Arctic, and Antarctica, causing the global sea level to drop by nearly 100 meters. Today, the Taiwan Strait, the East China Sea, the Yellow Sea, and the Bohai Sea are about 100 meters deep, so these areas were exposed as land at that time, and Taiwan, Japan, and mainland China were connected. Therefore, it's not surprising that fishermen in the Bohai Sea and the Taiwan Strait have found fossils of land-based rhinos and deer from 18,000 years ago, and that Japan has discovered stone tools from this period that are very similar to those found in China. From 15,000 years ago to the present, the Earth has gradually warmed up and entered an interglacial period, during which much of the continental ice has gradually melted, causing the sea level to rise by nearly 100 meters, so the Taiwan Strait, the East China Sea, the Yellow Sea, and the Bohai Sea have been flooded by seawater again.
The study of ancient climate is of great significance. What exactly causes the changes in the Earth's climate? Are there any regular patterns to these changes? Will the Quaternary glacial period last more than 10 million years like previous glacial periods? When will the current interglacial period end? Will the arrival of a new glacial period be beneficial or harmful to humans? These questions all need to be explored and studied by people.