What is the Global Geology website?
A global geology website is both an archive of stratigraphic information and a portal to the geology of the world. Like a cross between Google Maps and Wikipedia, globalgeology.com uses a geological map of the world (1:10,000,000) as an interface to help users locate and enter geological information. This information includes not only stratigraphic descriptions, but also digital images of outcrops and stratigraphic sections, and links to supporting earth science websites.
How do I use this site?
You can do two things at this site: 1) browse geological information, or 2) enter geological information.
How do I browse the geological information stored at this website?
Simple. Think of someplace on the globe that you would like to learn more about. You may be curious about the geology at that location. Click in the general vicinity of that area on the "Global Map" on the Home Page. A new "Regional Map" will appear. Click again on the area of interest. A new "Local Area Map" will appear. The Local Area Map is a one by one degree, latitude and longitude grid. To help you locate yourself, the map includes major cities, highways (red) and rivers.
You may notice that some of the one degree squares have colored triangles in the upper right-hand corner. A colored triangle indicates that geological information is available in that grid square. Click on a one degree square that has a colored triangle in the upper right-hand corner of the square. (If there are no squares with triangles, that means no data has been entered for that latitude/longitude grid square. Go back the regional map and try another areas.)
After you click on a local grid square with a triangle in the upper right-hand corner, a stratigraphic column will appear. This is the summary startigraphic column for that grid square. If you scan the stratigraphic column you may notice that some of the stages have small numbers in the upper left hand corner. These numbers indicate how many startigraphic sections have been entered for that stage.
If you click on any stage that has a small number in the right-hand corner, a description of the geology for that grid square at that geological time will be displayed.
How do I enter geological data at the Global Geology website?
In order to enter geological data you must first register. Go back to the Home page and enter "Register". Once you've registered you can "Logon"
After you "Logon" you can zoom to any latitude/longitude grid square and enter data for any geological stage. To enter data, simply click-on a stage name. A data entry form will appear. Follow the instructions on the data entry form. Most of the choices are check boxes or pull-down items.
When you are finished entering data, click on the "Submit Data" button and your geological description will be sent to the Global Geology database and will be added to the website.
Do I really need to register?
You can browse the geological data on the website without registering, but to enter new geological data you must register with Global Geology. Other future advantages to registration will include: web forums and user-groups on the geology of particular region or a particular time interval, access to digital downloads of the geological data, a free subscription to the web journal "30 by 30", and 20% discounts on all PALEOMAP Project teaching materials and software.
Where does the information stored at the Global Geology website come from?
The information stored at global geology.com comes in small part
from legacy databases such as the Paleogeographic Atlas Project
Lithologic database, the Paleobiology database, and the PALEOMAP
Project Lithologic Indicators of Climate database (over 250,000
combined entries). The bulk of the information, however, comes from
the worldwide community of geologists, and like Wikipedia, the global
geology website is an editable, community effort. The concept is
simple and is based on the premise that every geologist has a
favorite outcrop or intimately knows the geology of a few special
places. The Global Geology user interface makes it possible to
quickly and easily enter a description of any outcrop, worldwide.
What happens to the geological information that I enter?
The geological information is stored in an SQL database and the
geological map of the world and the stratigraphic time chart are
updated indicating that new data has been archived. If another
visitor to the global geology website selects the same time-patch, he
can review the geological information, download the information, or
enter an updated record. As the number registered users increases
and as more information is entered, the individual patches of
geological description will merge to form a nearly complete
four-dimensional map and database of the geology of the world through
What are the little colored triangles that appear in the upper right-hand corner of the one degree grid squares?
The colored triangles in the upper right-hand corner of some of the grid squares indicates that geological information has been entered for that grid square.
Can I only enter outcrop data?
No. You can enter both outcrop data and subsurface data. In the data entry form there is a field for "depth". Outcrop data has an assumed depth of zero meters (0). To enter subsurface data you must know the depth of the stratigraphic unit being described.
What if I know the exact latitude/longitude of the site?
If you know the exact latitude/longitude of the site that you are interested in, you can enter it directly in the latitude/longitude "go box" on the Home Page. This is a more precise way to enter data.
How do I contact other global geologists?
If a registered user agrees to submit an email address, then this information is available to all users of the Global Geology website.
I have a large geological dataset. Is there any faster way to enter data?
Yes, there are batch data entry methods. If you have a large data set that you would like to include in the Global Geology database contact Chris Scotese. Email: chris (at) gmail (dot) com.
What is the "30 by 30" web journal?
Once the GlobalGeology website has been up and running for a while, and a critical mass of data entries has been achieved, all registered users will receive bi-monthly copies of the "30 by 30" web journal. The "30 by 30" web journal will be a digital summary of the geological data for a 30 degree by 30 degree region of the Earth. This summary will describe the geologic, plate tectonic, paleogeographic and paleoclimatic evolution of this region through geological time.
What if I would like to enter information about more than one formation or outcrop in a 1x1 degree grid cell?
The geological description must describe all the units of that particular time interval at the chosen 1 x 1 degree grid cell. The smallest describable time interval is the geological "stage". The geological description must be a description of all the rock formations or groups in that stage. Only one entry per user is allowed.
What if a particular rock formation of groups spans two or more stages?
If the same rock unit spans more than one stage you can either,
1) use a large rock interval, i.e. epoch or period, or
2) "copy and paste" the information from one stage description into a second stage description. See the special "Copy to Clipboard" button. Be sure to copy to clipboard before you submit a new record.
What if there are more than one outcrop in a 1 x 1 degree grid square?
The geological description represents the "average" geology for the entire grid square. Only one entry per user is allowed.
Who built this website?
The Global Geology website was designed by Christopher R. Scotese, Director of the PALEOMAP Project. The programming behind the website was done by Carl Dreher, Focus Research.
How were the PaleoGlobes were made?
The downloadable Paleoglobes are the result of nearly 40 years of research and mapmaking by C. R. Scotese, Director of the PALEOMAP Project. The goal of the PALEOMAP Project is to illustrate the plate tectonic development of the ocean basins and continents, as well as the changing distribution of land and sea during the past 1100 million years. Beginning with the publication of the first continental drift "flip book" and computer animation illustrating plate motions (Scotese, 1975a&b, 2003), the paleoglobes are Scotese's most recent interpretation of the history of Earth's dynamic plates.
The paleoglobes in GlobalGeology are taken directly from the maps in the PALEOMAP PaleoAtlas for ArcGIS (Scotese, 2011 a-c). The PaleoAtlas is a digital map database that contains several hundred full-color paleogeographic maps illustrating the distribution of ancient mountain ranges, paleo-shorelines, active plate boundaries, and the extent of ancient paleoclimatic belts.
Additional information describing the information and methods used to produce the plate tectonic and paleogeographic maps is available at the PALEOMAP website (http://www.scotese.com). A brief overview of the "Paleogeographic Method" is described at the very end of this help section.
Scotese, C.R., and Baker, D.W., 1975. Continental drift reconstructions and animation, J. Geol. Educ., 23: 167-171.
Scotese, C.R., 1975. Continental Drift Flip Book, 1st edition. Chicago, Illinois.
Scotese, C.R., 2004. A continental drift Flipbook, Journal of Geology, v. 112, p. 729-741.
Scotese, C.R., 2011a, The PALEOMAP Project PaleoAtlas for ArcGIS, Volume 1, Cenozoic Paleogeographic and Plate Tectonic Reconstructions, version (9.2r), PALEOMAP Project, Arlington, Texas.
Scotese, C.R., 2011b, The PALEOMAP Project PaleoAtlas for ArcGIS, Volume 2, Cretaceous Paleogeographic and Plate Tectonic Reconstructions, version (9.2r), PALEOMAP Project, Arlington, Texas.
Scotese, C.R., 2011c, The PALEOMAP Project PaleoAtlas for ArcGIS, Volume 3, Jurassic and Triassic Paleogeographic and Plate Tectonic Reconstructions, version (9.2r), PALEOMAP Project, Arlington, Texas.
Scotese, C.R., 2011d, The PALEOMAP Project PaleoAtlas for ArcGIS, Volume 4, Late Paleozoic Paleogeographic and Plate Tectonic Reconstructions, version (9.2r), PALEOMAP Project, Arlington, Texas.
What are the Sources of Information?
PaleoGlobes - The paleoglobes in GlobalGeology are from the PALEOMAP PaleoAtlas (Scotese, 2011a-c).
Time Scale - The time scale used in GlobalGeology is based on the International Commission of Stratigraphy (ICS) time scale. Copies of the timescale can be downloaded at - http://www.stratigraphy.org/ics%20chart/09_2010/StratChart2010.pdf. The best source for information about the ICS timescale is Ogg et al. (2008), and the monumental Gradstein et al. (2004).
Gradstein, F.M., Ogg, J.G., and Smith, A., 2004. A Geologic Time Scale, Cambridge University Press, Cambridge, U.K., 589 pp.
Ogg, J.G., Ogg, G., and Gradstein, F.M., 2008. The concise Geologic Time Scale, Cambridge University Press, Cambridge, U.K., 177 pp.
Is this stuff for real? How do we really know all of this?The Paleogeographic Method
Well, if you really want to know, these maps are called "paleogeographic maps". They show the past location of the continents and our best estimates of the heights of mountains and the depth of the oceans. We make paleogeographic maps using the "paleogeographic method". This technique was invented by A. M. Ziegler, and further developed by his student, C. R. Scotese.
The study of paleogeography has two principle goals. The first goal is to map the past positions of the continents. The second goal is to illustrate the changing distribution of mountains, lowlands, shallow seas, and deep ocean basins through time.
Mapping the Past Positions of the Continents
The past positions of the continents can be determined using the following five lines of evidence: paleomagnetism, linear magnetic anomalies, paleobiogeography, paleoclimatology, and geologic history.
Mapping the Changing Distribution of Mountains, Lowlands, Shallow Seas and Deep Ocean Basins
- Paleomagnetism. By measuring the remanent magnetic field often preserved in iron-bearing rock formations, paleomagnetic analysis can determine whether a rock was magnetized near the Pole or near the Equator. Paleomagnetism provides direct evidence of a continent's N-S (latitudinal) position, but does not constrain its E-W (longitudinal) position.
- Linear Magnetic Anomalies. The Earth's magnetic field has another important property. Like the Sun's magnetic field, the Earth's magnetic field "flips" or reverses polarity. Fluctuations, or "anomalies", in the intensity of the magnetic field, occur at the boundaries between normally magnetized sea floor, and sea floor magnetized in the "reverse" direction. The age of these linear magnetic anomalies can be determined using fossil evidence and radiometric age determinations. Because these magnetic anomalies form at the mid-ocean ridges, they tend to be long, linear features (hence the name "linear magnetic anomalies") that are symmetrically disposed about the ridges axes. The past positions of the continents during the last 150 million years can be directly reconstructed by superimposing linear magnetic anomalies of the same age.
- Paleobiogeography. The past distribution of plants and animals can give important clues concerning the latitudinal position of the continents as well as their relative positions. Cold-water faunas can aften be distinguished from warm-water faunas, and ancient floras both reflect paleo-temperature and paleo-rainfall. The similarity or dissimilarity of faunas and floras on different continents can be used to estimate their geographic proximity. In addition, the evolutionary history of groups of plants and animals on different continents can reveal when these continents were connected or isolated from each other.
- Paleoclimatology. The Earth's climate is primarily a result of the redistribution of the Sun's energy across the surface of the globe. It is warm near the Equator and cool near the Poles. Wetness, or rainfall, also varies systematically from the equator to the pole. It is wet near the equator, dry in the subtropics, wet in the temperate belts and dry near the poles. Certain kinds of rocks form under specific climatic conditions. For example coals occur where it is wet, bauxite occurs where it is warm and wet, evaporites and calcretes occur where it is warm and dry, and tillites occur where it is wet and cool. The ancient distribution of these, and other, rock types can tell us how the global climate has changed through time and how the continents have traveled across climatic belts.
- Geologic and Tectonic History. In order to reconstruct the past positions of the continents it is necessary to understand the development of the plate tectonic boundaries that separate continents and bring them back together again. Only by understanding the regional geological and tectonic evolution of an area can you determine the location and timing of rifting, subduction, continental collision and other major plate tectonic events.
Some paleogeographic features change very slowly and are easy to map. Other paleogeographic features change very rapidly and, therefore, any map, at best, is an approximation. In this regard, the Earth, since the early Precambrian, has been divided into deep ocean basins (average depth 3.5 km) and high-standing continents (average elevation about 800 meters). Continental lithosphere, because it is less dense, is more bouyant and is not easily subducted, or recycled back into the Earth's interior. As a result, continents are made-up of very old rocks, some dating back 3.8 billion years. The amount of continental lithosphere has probably changed very little during the last 2.6 billion years (possibly increasing 10-15%). What has changed, is the shape and the distribution of continents across the globe. The ocean basins, on the other hand, are all less than 150 million years old. Oceanic lithosphere, because it is more dense is continually recycled back into the interior of the Earth.
In contrast to the continents and ocean basins, which are permanent geographic features, the height and location of mountain belts and the shape of the Earth's shorelines constantly change. Mountain belts either form where oceanic lithosphere is subducted beneath the margin of a continent, giving rise to a linear range of mountains, like the Andes mountains of western South America, or where continents collide forming, high mountains and broad plateaus like the Himalayan mountains and Tibetan Plateau of central Asia. Less extensive mountains can also form when continents rift apart (e.g. East African Rift), or where hot spots form volcanic uplifts.
In most cases mountain ranges take 10's of millions of years to form, and depending on the climate, may last for 100's of millions of years. Though the Appalachian mountains of the eastern United States were formed over 300 million years ago, due to the collision of North America and western Africa, remnants of this collisional mountain belt still reach heights of over than 2000 meters. The Himalayan Mountains, the world's tallest mountain range, began to rise from the sea nearly 50 million years ago when northern India collided with Eurasia. On the paleogeographic maps shown in this atlas, the extent of the mountain ranges increases during the collisional phase and is slowly reduced, by erosion, in subsequent maps.
In comparison to topographic features such as mountain ranges, the Earth's shorelines are ephemeral. The familiar shapes that characterize today's shorelines such as Hudson's Bay, the Florida peninsula, or the numerous fiords of Norway, are all less than 12,000 years old. The shape of the modern coastlines is the result of a 70 meter rise in sea level that took place in the last 12,000 years after the last great ice sheet that covered much of North America and Europe had melted.
It is important to note that the shoreline, though the edge of land, is not the edge of the continent. In most cases, the continent extends seaward 100's of kilometers beyond the shoreline. The actual edge of the continent is marked by the transition from the continental slope to the continental rise . This steep bathymetric gradient marks the boundary between continental lithosphere and oceanic lithosphere and is marked by the transition from light blue (shallow shelf) to dark blue (deep ocean).
The position of the shoreline is a function of both continental topography and sea level. Though topography changes slowly (10's of millions of years), global sea level can change rapidly (10's of thousand of years). Several factors can affect sea-level change. As we have seen, one of this factors in the amount of ice on the continents. At times when the continents were covered by great ice sheets, sea level was low and the continents were exposed. The last glacial maximum was 18,000 years ago. For the last 20 million years, the continents have been largely high and dry because there has been extensive mountain building in Asia and there has been significant ice on Antarctica. Other important global episodes of glaciation occurred 300, 450 and 650 million years ago. The oldest known glacial episode occurred in the Precambrian, approximately 2.2 billion years ago.
Sea level also changes more slowly (10's of millions of years) due to changes in the volume of the ocean basins. Water from the interior of the Earth, erupted as gas in volcanic eruptions, condensed on the cooling surface of the Earth to form the world's oceans. However, there has been no significant addition to the volume of water on the Earth since early Precambrian times.Changes in sea level, therefore, are not due to changes in the amount of water on the Earth, but rather are due to changes in the shape and size of the ocean basins.