Critical zone

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The Critical Zone is a dynamic system that extends from the top of the canopy to the bottom of groundwater aquifers. This zone includes the land surface, vegetation, the  and water bodies where a series of systems and processes interact and is the most heterogeneous portion of Earth.

Diagram of Earth's Critical Zone



The critical zone (CZ) is a term coined by the US National Research Council in 2001 and makes up the thin outer layer of Earth’s surface, extending from the top of the vegetation canopy down to groundwater. The CZ involves a mix of biological, physical and chemical processes. Scientific knowledge from a variety of fields is needed to understand the zone and its processes. These include the studies of geology, soil science, biology, ecology, geochemistry, hydrology, geomorphology, atmospheric science, and much more. The complex processes come together in the CZ to transform rock and biomass into soil, which is the main component of the CZ. This goes on to support much of the Earth’s biosphere, including humanity. The structure and functioning of the CZ has evolved in as a result of climate and tectonic changes throughout history. CZ science provides basic knowledge of Earth’s surface with “green” initiatives to stop continuing land use and climate change. Biogeochemical interfaces like ones that connect rock, water, air, organic matter, and organisms, are important to the functioning of the CZ. Studies vary throughout the different research sites of the world. Using the Penn State Integrated Hydrologic Model (PIHM) scientists have determined the age of water within a watershed by measuring levels of oxygen and hydrogen at different points in the critical zone such as in rain, in water within the soil, in groundwater, in streams.

Human Impact

The CZ is increasingly impacted by human activities including land and resource use, pollution, and climate change. Combining the many professions studying this complex subject has promoted a world network of research platforms that allow access to the CZ in a wide range of geologic settings. It is understood that to ecologists, the Critical Zone is an ecosystem or a watershed explaine Kathleen Lohse, who directs the new Reynolds Creek Critical Zone Observatory in southwest Idaho and co-organized a meeting session on critical zone ecology.


The proceses within the CZ occur across time frames that ranges from multi million-year spaces of tectonics to short spanning processes like water cycling. Recent CZ studies have suggested that the present landscape has been shaped through geologic time frames, and such geologic history can provide scientific knowledge and help decision support to predict future CZ changes. Recent advances in Earth science has advanced the ability to develop Earth system models to represent a wide variety of processes that may come about under different climate conditions. Critical Zone science also creates new modeling opportunities to integrate Earth surface processes. Hence, similar efforts are needed to provide detailed CZ models or models and databases. Knowledge of CZ structure and its evolution in time and space is very important to understanding the CZ processes and predicting results of future climate changes.

Critical Zone Observatories

The development of Critical Zone Observatories (CZOs) began in 2007. There are currently 62 CZOs globally, with the majority in North America and Europe.


The National Science Foundation is attempting to create a networked set of CZOs that will answer the tough scientific questions concerning the various scientific disciplines and their aspects that affect critical zone system workings. As said by Lohse "The goal of this... is to put the CZOs on the radar and get ecologists to see them as resources and to propose and conduct research,” . The Critical Zone Processes Team seek to quantify processes and properties of the surface and near subsurface.

List of Observatories

No. CZO Location
1 Adirondack Mountains South-western Adirondacks
2 AGRHYS Brittany
3 AMMA-CATCH S-N ecoclimatic gradient in West Africa
4 Damma Glacier Canton Uri, Switzerland
5 Bonanza Creek LTER Alaska
6 Boulder Creek Critical Zone Observatory Colorado Front Range, Rocky Mountains
7 Calhoun LTSE Southern Carolina
8 Central Great Plains Colorado
9 Christina River Basin CZO South-eastern Pennsylvania and Northern Delaware
10 Clear Creek Iowa
11 DRAIX-BLEONE French South Alps
12 Rivière des Pluies Erorun Réunion Island, Indian Ocean
13 French Karst observatory Languedoc, Jura, Provence, Pyrénées, Paris Basin, aquitanien Basin
14 Fuchsenbigl East Austria
15 Galapagos CZO Santa Cruz Island, Galapagos 
16 Guadeloupe Guadeloupe, French West Indies
17 Hawaii Hawaii
18 Hoffman Creek site Oregon
19 Hubbard Brook Experimental Forest New Hampshire
20 HYBAM: Hydrological and geochemical observatory of the Amazon Basin Amazon drainage basin
21 Illinois River Basin Illinois
22 Jemez River Basin CZO New Mexico
23 Kindla Kindla, Bergslagen
24 Koiliaris River Basin East Chania, Crete
25 Lowlands CZO Netherlands
26 Luquillo Luquillo, Puerto Rico
27 Lysina Slavkov Forest
28 Marcellus shale Pennsylvania
29 Merced River Chronosequence California
30 MONTOUSSE Gascogne
31 MSEC (management of soil erosion consortium) SE Asia (3 sites)
32 MSEC Dong Cao long term monitoring catchments 20°57'40"N -105°29'10"E
33 MSEC Houay Panoi long term monitoring catchments 19°51'10"N - 102°10'45"E
34 Mule Hole (Bandipur National Park)  Southern India (Mule Hole : 11° 72' N 76° 42 E)
35 Muskingum Watershed Ohio
36 Na Zelenem Western Bohemia
37 NC2 New Caledonia
38 NevCAN, Sheep Range and Snake Range Transects (NevCAN) Southern and East Central Nevada  
39 North Ogilvie Mountains  Yukon Territory
40 North-eastern Soil Monitoring Cooperative North-eastern Soil Monitoring Cooperative
41 Nsimi Cameroon 
42 OBSERA Guadeloupe (Lesser Antilles)
43 OHM-CV Cevennes-Vivarais (4 sites)
44 OMERE Brie, Paris Basin
45 ORACLE Languedoc and Cap Bon (2 sites)
46 Panola Mountain Atlanta
47 Pluhuv Bor Slavkov Forest
48 Plynlimon Mid Wales
49 Red Soil Site Yingtan, Jiangxi Province
50 Reynolds Creek Watershed Southwest Idaho
51 Santa Catalina Mountains CZO Saguaro National Park
52 SEQ peri-urban supersite South East Queensland
53 Southern Sierra Critical Zone Observatory Southern Sierra Nevada, California
54 Strengbach Vosges Mountains
55 Susquehanna Shale Hills Critical Zone Observatory Central Pennsylvania
56 Tenderfoot Creek Experimental Forest Montana, Southwest Alberta, and Wyoming
57 The Prairie Pothole Region CZO South Central North Dakota
58 The Rogers Glen (Shale Hills CZO) satellite site  Chadwicks, NY
59 Trindle Road Appalachian Trail Diabase Pennsylvania
60 TUM Critical Zone Observatory Bavaria
61 Beacon Farm 1 Rakaia River catchment, Canterbury Plains
62 Omere site ---

See also

Other closely related articles in this wiki include:


1. The Critical Zone Research Group [1]

2. The Critical Zone PSU [2]

3. Frontiers | How Deep Can Surface Signals Be Traced in the Critical Zone? Merging Biodiversity with Biogeochemistry Research in a Central German Muschelkalk Landscape | Biogeoscience [3]

4. Critical Zone Research and Observatories: Current Status and Future Perspectives [4]

5. Geophysics in the Critical Zone [5]

6. Ecology from treetop to bedrock: human influence in earth’s critical zone | Ecological Society of America. [6]

7. Policy relevance of Critical Zone Science. [7]

8. SoilTrEC- Critical Zone Observatories. [8]

9. Critical Zone Observatories | NSF - National Science Foundation. [9]

10. Critical Zone | Wyoming Center for Environmental Hydrology and Geophysics. [10]

External links

Relevant online sources to this wiki article include:

  • This is the news page of the Natural Science Foundation [11]
  • CZO Colorado [12]
  • CZO Luquillo [13]
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Critical zone
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