Note : The above story is based on materials provided by Wikipedia. Saturday, November 13, Sign in. Forgot your password?
Get help. Password recovery. Geology Page. Home Latest News Video. Debris Flow Dynamics. Sampling Hot Molten Lava. Incredible moment Anak Krakatau erupts, Oct Download Google Earth For Free. Remote Sensing Downloader. Thunder Egg. Home Geologic time scale Holocene Epoch. Geologic time scale.
Share on Facebook. Recommended For You Lower Triassic. Recommended For You Pridoli Epoch. In places that were previously covered in trees, farmers would remove them, dramatically changing the landscape. The natural regeneration of forest, with seeds growing into trees is broken by domesticated animals like sheep eating the young trees. The wide open mountains and fields of the British countryside, for example are entirely man-made. In a group of hunter-gatherers, groups of people tended to be small and most were involved in producing food.
As farming villages became towns, a group of people emerged who did not need to directly work to produce food. These people — kings, priests, merchants, craftsmen and others had the time to produce new things, like writing, organised religions, metal objects and so many other things.
In some places the nature of the farming required many people to work together. In the Mesopotamian basin modern-day Syria and Iraq , where some of the earliest towns were formed, systems of irrigation were required to get water from narrow rivers into broad areas of farmland. Technology itself sometimes also encouraged the growth of large kingdoms. Bronze is a metal alloy produced from a mixture of copper and tin.
In the eastern Mediterranean of Europe there is copper, but the tin had to come from far away, like Afghanistan or the British Isles. Only large kingdoms or empires had the resources to bring together such distant materials. The period of time when people are using Bronze is called the Bronze Age and it was followed by the Iron Age and so we are moving into history rather than geology. Even at the start of the Holocene, humans may have been causing extinctions of animals.
The rate of extinction has only grown since then, with no sign of stopping. Direct hunting is not the only cause. Farming landscapes are very different from ones untouched by man and while some animals have adapted rats, for example , many have not.
Some human impacts on the planet that we think of as modern are surprisingly old, for example pollution. Ancient layers of ice in the Greenland ice cap are a record of atmospheric pollution. Each layer is a record of ancient snow, plus trapped bubbles of air.
Studying this record shows traces of lead pollution from Roman mining in Spain from over years ago. Similar records from South America show the traces of local mining from years ago. These ancient traces of human activity are dwarfed by the current impacts.
During the Quaternary and most of the Holocene, CO2 levels slowly varied in step with Milankovitch cycles. Human burning of fossils fuels has dramatically changed this. Levels of CO2 are now higher than they have ever been before in the Holocene or even the Quaternary. Some geologists argue that the Holocene is over and that we are now in a new geological Epoch, that they call the Anthropocene.
First publication by Xiaoduo Media in Front Vision. It's official, we're in a new age; who knew? We have lots of new definitions that perhaps now contradict the Anthropocene Working Group and go against what most scientists perceive to be the most important change on Earth in the last 10, years.
But Prof Walker moved to clarify the situation: "To be frank, I see absolutely no conflict at all between the new subdivisions that we have here and a future designation of the Anthropocene. Image source, IUGS. The famous timeline will be updated to reflect the new "stages", or "ages", as they are called.
A portion of an Indian stalagmite that defines the beginning of the Meghalayan Age. A manifesto to save Planet Earth and ourselves 'Loneliest tree' records human epoch Search for Anthropocene 'golden spike'. The BBC is not responsible for the content of external sites. View original tweet on Twitter. Further changes to come? Most people are familiar with the last mass extinction that closed the Cretaceous Period 65 million years ago and resulted in the extinction of the dinosaurs.
Many scientists believe we are in the midst of a sixth mass extinction event caused by ourselves. Based on population numbers required to maintain genetic viability; it is estimated that as many as 30 percent of plant and animal species may become extinct within the next years. Habitat destruction is the leading cause of species extinction today. We have also had significant impacts on the geophysical characteristics of Earth.
Monoculture devoting large tracts of land to single crops has affected the composition and fertility of the soil in most arable parts of the world. This effect has been ameliorated by use of chemical fertilizers, but has not been eliminated. Depletion of aquifers has reduced the availability of free fresh water.
We base our division of geologic time on evidence of changes in the life forms present on Earth in different times. In the past, global climate change has often been synchronous with mass extinction.
0コメント