La glaciazione che congelò il mondo per 10.000 anni - Documentario Storia della Terra

Today, Earth enjoys a relatively stable climate, which has allowed the development of human civilizations. Yet, geologically speaking, not long ago, our planet went through a period when much of the Northern Hemisphere was trapped in extreme cold. For nearly 10,000 years, immense ice sheets covered entire continents, temperatures were much lower than today, and the landscape seemed to belong to another planet. This period was part of the last Ice Age. Its coldest phase, known as the Last Glacial Maximum, occurred between approximately 26,500 and 19,000 years ago. Subsequently, when the climate had already begun to warm, a sudden return of cold, known as the Younger Dryas or Younger Dryas, brought back near-glacial conditions for approximately 1,200 years. In the collective imagination, these long periods of freezing are often remembered as a time when ice seemed to have immobilized the world. During that period, enormous ice sheets covered Canada, the northern United States, Scandinavia, much of northern Europe, and vast regions of Asia. In some areas, the ice was over three kilometers thick. Its immense weight slowly deformed the Earth's crust, permanently altering the landscape. The oceans were also very different. A huge amount of water was trapped in the form of ice, causing sea levels to drop by about 120 meters compared to today. Vast coastal plains, now submerged, were then dry land that formed natural bridges between continents, allowing the migration of animals and early humans. One of the most famous examples is Beringia, the land bridge that connected Siberia to Alaska. According to most scholars, it was through this corridor that the first humans reached the American continent. The climate was extremely harsh. In many regions, average temperatures were several degrees lower than today. Winters lasted almost year-round, summers were short and cool, and fierce winds swept across the immense frozen plains. Paradoxically, many of these areas received little snowfall, giving rise to vast, cold deserts. Despite these extreme conditions, life still thrived. The immense glacial steppes were home to the woolly mammoth, the woolly rhinoceros, steppe bison, reindeer, wild horses, and gigantic deer. With their thick fur and layers of fat, these animals were perfectly adapted to the cold. Pursuing them were some of the most impressive predators of prehistory, such as the Smilodon in the Americas, giant wolves, cave bears, and numerous other large carnivores perfectly adapted to glacial ecosystems. Humans also had to learn to adapt. Our ancestors made clothing from animal skins, built shelters that could withstand the intense cold, used fire for warmth, and developed increasingly effective hunting techniques. Their extraordinary ability to adapt was crucial to surviving in an environment where food was scarce and the climate could become deadly. As the millennia passed, however, the climate slowly began to change. About 19,000 years ago, temperatures began to gradually rise. The gigantic ice sheets began to melt, pouring enormous quantities of freshwater into the oceans. Sea levels gradually rose, submerging coastal plains and land bridges that had connected the continents for thousands of years. This warming, however, was not continuous. About 12,900 years ago, the climate underwent a sudden cooling during the Younger Dryas. For over a millennium, near-glacial conditions returned to much of the Northern Hemisphere, before warming finally resumed. As the ice retreated, the planet changed radically. Forests slowly replaced the frozen steppes, rivers changed their courses, and many cold-adapted species began to disappear. Woolly mammoths, woolly rhinos, and numerous other Ice Age giants likely became extinct due to a combination of climate change and human hunting pressure. The end of this great glaciation marked the beginning of the Holocene, the geological epoch we still live in today. Without this gradual warming of the planet, agriculture, the first cities, and great human civilizations likely would never have arisen. The last great glaciation reminds us how profoundly the Earth's climate can change. This channel is an official affiliate of the ORBINEA STUDIO network.