At the dawn of life, also known as the Proterozoic Era, the huge rock layers that formed the outer surface of the earth's crust already existed in many places on the earth's surface, and when these rock layers were found under the cover accumulated on them by later generations, only fossils of plants and early hominids could be found in these rocks, but in some ancient layers of layered rocks also contained some fossils of early marine life, both animal and plant, and these fossil species included seaweeds, corals, primitive marine organisms, etc.; However, the absence of such fossils in earlier rock layers does not prove that life did not exist, because life was scarce in the early days and could only slowly spread to the surface; At present, the ancient age rocks that are close to the surface layer occupy only about 1.8 of the land area, and the average thickness of these oldest rock formations is about 15 miles, and some ancient rock formations can reach 4 miles thick in some places, but most of the rock formations thought to come from this era belong to a later period.
In North America, there are many of these ancient, fossilized rock formations exposed to the surface, they are found in the eastern and central parts of Canada, and there is also an east-west bridge composed of these rock formations, extending from Pennsylvania in the United States to the ancient Adirondack Mountains to the west, passing through Michigan and Wisconsin and Minnesota, and some bridges from Newfoundland to Alabama in Canada, and one bridge from Alaska to Mexico; This early age of rock formations is exposed all over the world, and the most obvious of them are the fossilized primitive rock formations found in Lake Superior and the Grand Canyon of the Colorado River, all of which have multiple geological age layers, thus confirming the environmental fluctuations and surface ups and downs of those distant eras, these rock formations are the oldest repositories of fossil data in the earth's crust, the crustal ups and downs caused by early ** and early volcanic eruptions, It brought the lava flow of that era and a lot of iron, copper, and lead to the earth's surface; There is hardly any other place on Earth that illustrates these conditions as vividly as the St. Croix River Gorge in Wisconsin, where there have been many successive lava flows, followed by flooding ages and frequent rock deposits, and although the sedimentary cores and faults of many lava flows no longer exist, and although the rock system has been buried in the bottom strata, there are still many visible records of ancient chronological strata.
In the primitive age of marine life, most of the coasts sank to the bottom of the sea, and many ancient sandstones and conglomerates represent the sedimentary accumulations of these ancient coasts, which are the sediments belonging to this early era, and which are directly pressed on those ancient rocks that are far beyond the age of life, and these ancient rocks are the materials that appeared in the global ocean age, and in these transitional rock accumulations, those rock accumulations that are closer to the surface layer contain a small amount of black shellfish or slate. These in turn represent the existence of carbon life and prove the existence of the ancestors of plant life; Much copper is also found in the cracks of these rocks, concentrated in the slow-flowing swampy waters of some of the old haven coastlines, while iron ore in North America and Europe is found in sedimentary and extruded rock formations, partly in older strata, and partly in later strata.
The history of the growth of the earth is told through these giant books of fossil pages that can be called the world's historical records, and these magnificent chapters of biogeological records accurately tell the evolutionary reality of our planet Earth; And many of those ancient seabeds are now high and rising on the top of the land, and these sediments of countless ages tell the epic of the struggle of life in those ancient years.
The epoch in which we walked the earth began a billion years ago and continued through five major epochs:
The first era: The epoch before the birth of life is the first 4500 million years, about the beginning of the planet Earth reached its current size, until before the creation of life, we geoscientists define this era as Archean.
The second era: The era of the birth of life is the next 1500 million years, this era connects two epochs, the early period includes the era before the birth of life, which can also be called the period of great change; The later period includes the era of the subsequent more advanced development of marine life, which is also known as the Protozoic by our Earth explorers.
The third era: The era of marine life is the next 2500 million years, commonly known as the Paleozoic Era; The initial seabed of this era was an extension of the continental shelf, and the vast shallow nearshore basins were already filled with pre-epochal plant life, and some of the simpler and more primitive animal life had slowly emerged from the highly evolved plant ecosystems, and the early marine biosphere had gradually spread along the long and continuous coastline land, and eventually filled the inland seas with many primitive marine life.
The Fourth Era:The early era of terrestrial life is the next 100 million years, and this era is also commonly known as the Mesozoic Era.
The fifth eraThe Mammalian Era is the last 50 million years of the era of terrestrial life, and this era is also known as the Cenozoic.