The Cenozoic Era is Earth's current geological era, representing the last 66 million years of Earth's history. It is characterized by the dominance of insects, mammals, birds and angiosperms. It is the latest of three geological eras of the Phanerozoic Eon, preceded by the Mesozoic and Paleozoic. The Cenozoic started with the Cretaceous–Paleogene extinction event, when many species, including the non-avian dinosaurs, became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor.
Erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy and geochronology. It is used primarily by Earth scientists to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardised international units of geological time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC) that are used to define divisions of geological time. The chronostratigraphic divisions are in turn used to define geochronologic units.
The Holocene is the current geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene is an interglacial period within the ongoing glacial cycles of the Quaternary, and is equivalent to Marine Isotope Stage 1.
The Holocene extinction, also referred to as the Anthropocene extinction, is an ongoing extinction event caused by human activities during the Holocene epoch. This extinction event spans numerous families of plants and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, impacting both terrestrial and marine species. Widespread degradation of biodiversity hotspots such as coral reefs and rainforests has exacerbated the crisis. Many of these extinctions are undocumented, as the species are often undiscovered before their extinctions.
The Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the Phanerozoic eon. It follows the Neogene Period and spans from 2.58 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene and the Holocene ; a proposed third epoch, the Anthropocene, was rejected in 2024 by IUGS, the governing body of the ICS.
Biomass is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass, which is the mass of all species in the community. It can include microorganisms, plants or animals. The mass can be expressed as the average mass per unit area, or as the total mass in the community.
The lunar geological timescale divides the history of Earth's Moon into five generally recognized periods: the Copernican, Eratosthenian, Imbrian, Nectarian, and Pre-Nectarian. The boundaries of this time scale are related to large impact events that have modified the lunar surface, changes in crater formation through time, and the size-frequency distribution of craters superposed on geological units. The absolute ages for these periods have been constrained by radiometric dating of samples obtained from the lunar surface. However, there is still much debate concerning the ages of certain key events, because correlating lunar regolith samples with geological units on the Moon is difficult, and most lunar radiometric ages have been highly affected by an intense history of bombardment.
In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role. Ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not.
The Anthropocene is a now rejected proposal for the name of a geological epoch that would follow the Holocene, dating from the commencement of significant human impact on Earth up to the present day. It was rejected in 2024 by the International Commission on Stratigraphy in terms of being a defined geologic period. The impacts of humans affect Earth's oceans, geology, geomorphology, landscape, limnology, hydrology, ecosystems and climate. The effects of human activities on Earth can be seen for example in biodiversity loss and climate change. Various start dates for the Anthropocene have been proposed, ranging from the beginning of the Neolithic Revolution, to as recently as the 1960s. The biologist Eugene F. Stoermer is credited with first coining and using the term anthropocene informally in the 1980s; Paul J. Crutzen re-invented and popularized the term. However, in 2024 the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS) rejected the Anthropocene Epoch proposal for inclusion in the Geologic Time Scale.
Human impact on the environment refers to changes to biophysical environments and to ecosystems, biodiversity, and natural resources caused directly or indirectly by humans. Modifying the environment to fit the needs of society is causing severe effects including global warming, environmental degradation, mass extinction and biodiversity loss, ecological crisis, and ecological collapse. Some human activities that cause damage to the environment on a global scale include population growth, neoliberal economic policies and rapid economic growth, overconsumption, overexploitation, pollution, and deforestation. Some of the problems, including global warming and biodiversity loss, have been proposed as representing catastrophic risks to the survival of the human species.
The anthroposphere refers to that part of the Earth system that is made or modified by humans for use in human activities and human habitats. The term has been suggested for inclusion as one of the Earth's spheres, while others use the related term technosphere. The term "anthroposphere" was first coined by Austrian geologist Eduard Suess in 1862.
The Early Anthropocene Hypothesis is a stance concerning the beginning of the Anthropocene first proposed by William Ruddiman in 2003. It posits that the Anthropocene, a proposed geological epoch coinciding with the most recent period in Earth's history when the activities of the human race first began to have a significant global impact on Earth's climate and ecosystems, dates back to 8,000 years ago, triggered by intense farming activities after agriculture became widespread. It was at that time that atmospheric greenhouse gas concentrations stopped following the periodic pattern of rises and falls that had accurately characterized their past long-term behavior, a pattern that is explained by natural variations in Earth's orbit known as Milankovitch cycles. Ruddiman's proposed start-date has been met with criticism from scholars in a variety of fields.
Environmental issues are disruptions in the usual function of ecosystems. Further, these issues can be caused by humans or they can be natural. These issues are considered serious when the ecosystem cannot recover in the present situation, and catastrophic if the ecosystem is projected to certainly collapse.
Planetary boundaries are a framework to describe limits to the impacts of human activities on the Earth system. Beyond these limits, the environment may not be able to self-regulate anymore. This would mean the Earth system would leave the period of stability of the Holocene, in which human society developed. The framework is based on scientific evidence that human actions, especially those of industrialized societies since the Industrial Revolution, have become the main driver of global environmental change. According to the framework, "transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental-scale to planetary-scale systems."
The Noachian is a geologic system and early time period on the planet Mars characterized by high rates of meteorite and asteroid impacts and the possible presence of abundant surface water. The absolute age of the Noachian period is uncertain but probably corresponds to the lunar Pre-Nectarian to Early Imbrian periods of 4100 to 3700 million years ago, during the interval known as the Late Heavy Bombardment. Many of the large impact basins on the Moon and Mars formed at this time. The Noachian Period is roughly equivalent to the Earth's Hadean and early Archean eons when Earth's first life forms likely arose.
The carbon cycle is an essential part of life on Earth. About half the dry weight of most living organisms is carbon. It plays an important role in the structure, biochemistry, and nutrition of all living cells. Living biomass holds about 550 gigatons of carbon, most of which is made of terrestrial plants (wood), while some 1,200 gigatons of carbon are stored in the terrestrial biosphere as dead biomass.
Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in biological diversity in a given area. The decrease can be temporary or permanent. It is temporary if the damage that led to the loss is reversible in time, for example through ecological restoration. If this is not possible, then the decrease is permanent. The cause of most of the biodiversity loss is, generally speaking, human activities that push the planetary boundaries too far. These activities include habitat destruction and land use intensification. Further problem areas are air and water pollution, over-exploitation, invasive species and climate change.
Pyrocene is a proposed term for a new geologic epoch or age characterized by the influence of human-caused fire activity on Earth. The concept focuses on the many ways humans have applied and removed fire from the Earth, including the burning of fossil fuels and the technologies that have enabled people to leverage their influence and become the dominant species on the planet. The Pyrocene offers a fire-centric perspective on human history that is an alternative to or complementary term for the Anthropocene. Like the Anthropocene, the concept suggests that human activity has shaped the Earth's geology and identifies fire as humanity's primary tool for shaping the planet and its environment.
The decline of wild mammal populations globally has been an occurrence spanning over the past 50,000 years, at the same time as the populations of humans and livestock have increased. Nowadays, the total biomass of wild mammals on land is believed to be seven times lower than its prehistoric values, while the biomass of marine mammals had declined fivefold. At the same time, the biomass of humans is "an order of magnitude higher than that of all wild mammals", and the biomass of livestock mammals like pigs and cattle is even larger than that. Even as wild mammals had declined, the growth in the numbers of humans and livestock had increased total mammal biomass fourfold. Only 4% of that increased number are wild mammals, while livestock and humans amount to 60% and 36%. Alongside the simultaneous halving of plant biomass, these striking declines are considered part of the prehistoric phase of the Holocene extinction.
