China ancient myth legend thinks, before heaven and earth has not formed, the universe is like a "big egg", dark, chaotic a ball, there is no light inside, there is no sound. At this time, a Pangu appeared. He used his divine axe to chop at this chaos. The light qi floated upward and became the sky; the heavy qi sank downward and became the earth. Later, when Pangu died, various parts of his body became the sun, moon, stars, mountains, rivers, vegetation, etc. Of course, this is just a myth about Pangu's creation. However, scientists have indeed been working on how continents and oceans on earth were formed.
The total surface area of the earth today is approximately 5.1×10^8 square kilometers. Among them, the land area accounts for about 29% of the total surface area, and the ocean area accounts for about 71% of the total surface area. The distribution of land and oceans on the earth is extremely uneven. The land is mainly distributed in the northern hemisphere, accounting for about 67.5% of the total land area. The land-sea area ratio in the northern hemisphere is approximately 1.5: 1, and in the southern hemisphere it is approximately 4.2: 1. Has the location of the oceans and land remained unchanged from the formation of the earth to the present? The answer is no. So where would the land in the past be?
In 1915, German meteorologist Wigner completed the book "The Origin of Land and Sea", which comprehensively and systematically elaborated on the "theory of continental drift." He believes that about 200 million years ago, various continents around the world were put together to form a supercontinent-Pangea (derived from Greek, meaning "the entire land"), also known as the "United Palaea" or "Pangea". Among them, a series of continents in the north include North America, Eurasian continents (excluding the Arabian Peninsula and the Indian Peninsula), etc., and are called Laurasia; a series of continents in the south include South America, Africa, India, the Arabian Peninsula, Australia, etc., and are called Gondwana. Compared with the current position of continents, Pangaea is generally located much south. The ocean surrounding this "pan-continent" is called the "pan-ocean" or the "ancient Pacific", and the entire "pan-ocean" is connected around the world. At that time, at the end of the Triassic in the geological period (about 200 million years ago), China's North China, South China and other regions had not yet been combined into the current overall continent.
Subsequently, Pangaea began to disintegrate and separate in three stages, and its fragments drifted. The first stage occurred during the Jurassic Period (about 180 million years ago), when Africa and North America first broke up to form the North Atlantic Ocean. The second stage occurred at the beginning of the Cretaceous (about 140 million years ago), when South America and Africa separated to form the South Atlantic; at the same time, India, Australia and Antarctica separated to form the Indian Ocean; subsequently, the Atlantic Ocean and Indian Ocean gradually expanded. In the third stage, more than 50 million years ago, Australia separated from Antarctica and drifted north, and the North Atlantic Mid-Ocean Ridge extended into the Arctic Ocean. By two to three million years ago, drifting continents formed the current basic pattern of seven continents and five oceans.