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Earth history and time

  • Changing Paleoclimates and Mass Extinctions. This article provides a model for climatic change and relates climatic cycles with major extinction events in the history of the Earth. It discusses the mechanisms behind modern climate zones (circulation, storm systems, seasons), astronomical models, climatic models (obliquity conditions, rising sea levels, current conditions), and mass extinctions and model timing (causes of extinction events, predicted vs. documented extinctions, and extinction-driven evolution). A geologic time scale provides a reference for climatic conditions at different periods in Earth history. References are provided for additional information. (more info)
  • Climate TimeLine Information Tool. A narrative text with many embedded links to visualizations describes and illustrates aspects of paleoclimate climate. This NOAA site points out the different aspects of paleoclimate change that operate on different timescales. ( This site is likely no longer available. )
  • Dr. Bob's Geologic Time Page. This is a collection of mnemonic devices to aid in learning the various periods and epochs of the geologic time scale which the author has assembled from a variety of contributors. Contributor email addresses are included. There are also mnemonic devices for Moh's hardness scale and for stratigraphic sequences from the Canyonlands-San Juan River area and the Grand Canyon. (more info)
  • GSA Geologic Time Scale. This Geological Society of America (GSA) site contains a detailed geologic time scale as an educational resource. It may be downloaded to a larger size, and includes all Eras, Eons, Periods, Epochs and ages as well as magnetic polarity information. (more info)
  • Geologic History of Western US. This web-site is a presentation showing graphically the Proterozoic and Phanerozoic geologic history of the Southwestern United States. There is a text file providing a brief narrative of the geologic history, which links to map graphics for each period. The graphics contain a scale and have labeled features to better understand what is happening as time progresses. (more info)
  • Geologic Time. This site contains 24 questions on the topic of geologic time, which covers dating techniques and unconformities. This is part of the Principles of Earth Science course at the University of South Dakota. Users submit their answers and are provided immediate feedback. ( This site may be offline. )
  • Global Atlas of Paleovegetation since the Last Glacial Maximum. This set of preliminary, broad-scale vegetation/ecosystem map reconstructions covers several time frames, the Last Glacial Maximum (18,000 14C years ago), the early Holocene (8,000 14C years ago), and the mid Holocene (5,000 14C years ago). For comparison, 'present-potential' maps that may be regarded as approximating the late Holocene vegetation distribution as it would - or might - have been without agricultural modification are included. The reconstructions emphasize radiocarbon-dated evidence - whether palynological, sedimentological or zoological and, while subject to considerable speculation due to sparse data coverage in many areas, they represent perhaps the nearest representation available to a 'consensus picture' as based on published review sources and advice from approximately 100 specialists in all branches of the study of Quaternary environments. The Atlas is divided into six regions, Europe, Eurasia, Africa, Australasia, North America and South America, each of which is accompanied by a detailed key of that region's vegetation types, as well as a description of the subregion's principal sources of paleovegetative evidence. The site also covers the spatial resolution of the sites maps, geographical boundaries in relation to climate transitions, no-analogue vegetation types, and the prevalent uncertainties surrounding various debates in paleovegetation and paleoclimatology. (more info)
  • Isotope Tutorial . This isotope tutorial explains what isotopes are and what units are used to express them, how measurements of isotopes are made, and how natural variation in stable isotope abundances come about. The site describes processes affecting isotope ratios such as photosynthesis, evapotranspiration, and respiration; biosphere-atmosphere exchange of isotopes in water and carbon; and how stable isotopes are used to study environmental history. There is information on courses in stable isotopes and the Biosphere - Atmosphere Stable Isotope Network (BASIN) project aimed at improving understanding of carbon cycle processes at the ecosystem, regional, and global scale. Links are provided to analytical labs. ( This site may be offline. )
  • Mapping a Planet's Restless Past. This is an article by Andrew Campbell from The University of Chicago Magazine, December 1995. The article is about the Chicago's Paleogeographic Atlas Project, an effort Alfred Ziegler began in 1975 to chart Earth's changing face, from more than 500 million years ago to the present. The article contains four maps from the project: A Permian Supercontinent, Computers Rebuild Climates of the Paleozoic, Birth of an Ocean, and The Aging of the Appalachians. Each of the maps is accompanied by a paragraph describing them in detail. (more info)
  • National Oceanic and Atmospheric Administration: Paleoclimatology Program. This site is a clearinghouse of information, data and visualizations from NOAAs Paleoclimatology Program (more info)
  • Paleogeography Through Geologic Time. This website contains paleogeographic and plate tectonic reconstructions presented by Ron Blakey and Colorado Plateau Geosystems, Inc. Global images are available as mollewide (oval) globes, round globes, and rectangular maps in 27 time slices. More detailed regional maps are available for particular regions including Europe, North America, Colorado Plateau, and SW North America. (more info)
  • Paleomagnetism . This website about paleomagnetism contains images of True Polar Wander, The Cambrian Time Scale, Gondwana, Baltica, Laurentia, Rodinia, Panotia, Pangea, and more. It has links to other paleomag sites, access to Gondwana paleomagnetic database, and a list of publications (some of which have links to web versions). (more info)
  • Paleomap Project. Paleogeographic globes that move, tilt, and spin to allow viewing from different angles, and animated plate-tectonic maps that show plate movement and sea-floor spreading for different periods in earth history are available for purchase. Paleomap Project is the creation of Christopher R. Scotese at the University of Texas at Arlington. (more info)
  • Radioactive Decay Calculator. This online calculator computes radioactive decay, timed decay, and timed solid disposal for a databank containing 116 isotopes. It also features University of British Columbia disposal limits and a unit converter and date/time calculators. These tools calculate the half-life for selected isotopes; radioactive decay final activity, given the initial activity and decay time; the decay time, given the initial and final activities; and the decay time, given the mass of a solid and the initial activity. (more info)
  • Regional Paleogeographic Views of Earth History. Regional paleogeographic reconstructions of North America, Colorado Plateau, SW North America, and Mesozoic terrane accretion. These beautiful reconstructions by geologist Ron Blakey (formerly Northern Arizona University) and Colorado Plateau Geosystems, Inc. ( This site may be offline. )
  • University of California's Museum of Paleontology: Geologic Timeline. University of California's Museum of Paleontology has created a hyperlinked Geologic Timeline with all sorts of details about each time unit that may be useful later in the course. Each hyperlink contains a variety of information including stratigraphy, ancient life, localities and tectonics associated with that specific time period. Users can also link to an Introduction to Geology page and a description of the Museum's geology wing. (more info)