Paleomap
Encyclopedia
Paleomaps are map
s of continents and mountain ranges in the distant past or future. Until the 1960s, paleomaps were not very satisfactory as it was difficult to understand many quite distinctive features. For example huge river delta
s seemed to be associated with what must have been quite small drainage basins. With the discovery of plate tectonics
, it became apparent that land masses move relative to one another over time. Ancient geologic features started to make far more sense. It is now possible to construct maps that are probably fairly accurate for continental positions over several hundred million years. Before the Cambrian
era, it becomes much more difficult since there are fewer rock exposures preserved. The state of large regions of the Earth becomes unknowable in the distant past. Where rocks are exposed, latitudes can often be determined from the orientation of preserved magnetic fields (see paleomagnetism
) but longitudes are based on projections that are increasingly uncertain as one gets further from the present.
Many published maps are associated in one way or another with the work of Christopher Scotese
. The maps are useful since is usually quite difficult to describe the location and orientation of geographical features using words alone.
Map
A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....
s of continents and mountain ranges in the distant past or future. Until the 1960s, paleomaps were not very satisfactory as it was difficult to understand many quite distinctive features. For example huge river delta
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
s seemed to be associated with what must have been quite small drainage basins. With the discovery of plate tectonics
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
, it became apparent that land masses move relative to one another over time. Ancient geologic features started to make far more sense. It is now possible to construct maps that are probably fairly accurate for continental positions over several hundred million years. Before the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
era, it becomes much more difficult since there are fewer rock exposures preserved. The state of large regions of the Earth becomes unknowable in the distant past. Where rocks are exposed, latitudes can often be determined from the orientation of preserved magnetic fields (see paleomagnetism
Paleomagnetism
Paleomagnetism is the study of the record of the Earth's magnetic field in rocks. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. This record provides information on the past behavior of Earth's magnetic field and the past location of...
) but longitudes are based on projections that are increasingly uncertain as one gets further from the present.
Many published maps are associated in one way or another with the work of Christopher Scotese
Christopher Scotese
Christopher R. Scotese is geologist at the University of Texas at Arlington. He received his PhD from the University of Chicago in 1985. He is creator of the Paleomap Project, which aims to map Earth over the last billion years, and is credited with predicting Pangaea Ultima, a possible future...
. The maps are useful since is usually quite difficult to describe the location and orientation of geographical features using words alone.
External links
- For an overview of maps available on the Internet, see http://www.geology.about.com/science/geology/library/weekly/aa071298.htm/.
- Scotese maintains a reasonable selection of maps on his website http://www.scotese.com/. Several Universities post similar maps made using Scotese's software.
- Another important resource is the University of Chicago PaleoGeographic Atlas Project http://plates.uchicago.edu/.