Earth's critical zone is the “

heterogeneous Homogeneity and heterogeneity are concepts relating to the uniformity of a substance, process or image. A homogeneous feature is uniform in composition or character (i.e., color, shape, size, weight, height, distribution, texture, language, i ...

, near surface environment in which complex interactions involving rock, soil, water, air, and living

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

s regulate the natural habitat and determine the availability of life-sustaining resources” (National Research Council, 2001). The Critical Zone, surface and near-surface environment, sustains nearly all

terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...

life. The critical zone is an interdisciplinary field of research exploring the interactions among the land surface,

vegetation Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular Taxon, taxa, life forms, structure, Spatial ecology, spatial extent, or any other specific Botany, botanic ...

, and water bodies, and extends through the

pedosphere The pedosphere () is the Earth's crust, outermost layer of the Earth that is composed of soil and subject to soil formation processes. It exists at the interface of the lithosphere, Atmosphere of Earth, atmosphere, hydrosphere and biosphere. The ...

, unsaturated

vadose zone The vadose zone (from the Latin word for "shallow"), also termed the unsaturated zone, is the part of Earth between the land surface and the top of the phreatic zone, the position at which the groundwater (the water in the soil's pores) is at ...

, and saturated

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

zone. Critical Zone science is the integration of Earth surface processes (such as landscape evolution,

weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...

geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...

, and

ecology Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...

) at multiple spatial and temporal scales and across anthropogenic gradients. These processes impact mass and energy exchange necessary for

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

productivity, chemical cycling, and water storage. The critical zone is studied at

Critical Zone Observatories Critical Zone Observatories (CZO) is an interdisciplinary collaborative research project across nine institutions with the purpose of understanding the chemical, physical, geological, and biological processes that both shape the surface of Earth ...

, where multiple scientific communities study various aspects of the critical zone that can lead to synthesized understanding of complex systems.

History

Dimitrios Tsakalotos first introduced the term ''critical zone'' in chemistry literature in 1909 to describe the binary mixture of two fluids, but has since been adopted to refer to the "connection of vegetation to soil and weathered materials" by Gail Ashley in 1998. In October 2003, scientists attended the first Weathering System Science Workshop. Participants agreed to promote outreach activities to broaden the profile of involved Earth scientists and crafted a set of questions that would drive further development of Weathering System Science. This field of science was considered to include all aspects of chemistry, biology, physics, and geology of the critical zone. The Weathering System Science Consortium was established in early 2004 and later was changed to the Critical Zone Exploration Network (CZEN) in 2006. In October 2005 WSSC/CZEN solicitated a call for proposals to initiate seed sites that would help grow and establish a critical zone network. In total, ten sites have been awarded grants, and nine sites have received continued funding. In 2005, the

University of Delaware The University of Delaware (colloquially known as UD, UDel, or Delaware) is a Statutory college#Delaware, privately governed, state-assisted Land-grant university, land-grant research university in Newark, Delaware, United States. UD offers f ...

hosted an NSF-sponsored workshop that resulted in a call by scientists for an international initiative to study the critical zone. As key parts of that initiative, the scientists called for the development of an international Critical Zone initiative and a systematic approach to the investigation of processes in the critical zone across a broad array of sciences, including geology, soil science, biology, ecology, chemistry, geochemistry, geomorphology, and hydrology. A booklet, ''Frontiers in Exploration of the Critical Zone'', was produced from the meeting. On July 24, 2006 NSF posted a solicitation for proposals for Critical Zone Observatories (CZO) within the Division of Earth Sciences. Established in 2009, the Delaware Environmental Institute (DENIN) is a multidisciplinary initiative bringing together scientists, engineers, and policy specialists to provide solutions to pressing environmental needs and produce strategies to address emerging environmental challenges by conducting research and promoting and coordinating knowledge partnerships that integrate environmental science, engineering and policy. DENIN fosters a culture of scholarship that leverages the combined talents of affiliates and fellows through collaborative working groups, joint proposal development and, where synergistic, project resource coordination.

References

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External links

NSF-funded Critical Zone Observatory NetworkThe Critical Zone Exploration NetworkDelaware EPSCoR ScienceDelaware Environmental Institute
Structure of the Earth Soil science Hydrogeology