Paleomaps are
maps of continents and mountain ranges in the past based on
plate reconstructions. Until the 1960s, paleomaps were not very satisfactory, since it was difficult to understand many quite distinctive features. For example, huge
river delta
A river delta is a landform shaped like a triangle, created by deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more ra ...
s seemed to be associated with what must have been rather small drainage basins. With the discovery of
plate tectonics
Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large t ...
, 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
The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...
Period, 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 (or palaeomagnetismsee ), is the study of magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called ''paleomagnetists.''
Certain magnetic minerals in roc ...
) 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 it is usually quite difficult to describe the location and orientation of geographical features using words alone.
See also
*
* {{annotated link, Paleohydrology
External links
* For an overview of maps available on the Internet, se
* Scotese maintains a reasonable selection of maps on his websit
Several Universities post similar maps made using Scotese's software.
* Another important resource is the University of Chicago PaleoGeographic Atlas Projec
Map types
Plate tectonics