Dimensions of continents and oceans – water has carved a perfect cistern
Citable URI
https://hdl.handle.net/1912/9028As published
https://doi.org/10.1016/j.epsl.2017.03.017Keyword
Freeboard; Continental crust depth; Ocean depth; Continent area; Ocean area; Continental crust and water volumesAbstract
The ocean basins have almost exactly the correct surface area and average
depth to hold Earth’s water. This study asserts that three processes are responsible for
this. First, the crust is thickened by lateral compression from mountain formation.
Second, Earth’s continental crust is leveled by erosion. Third, due to the efficiency of
erosion, the average elevation is a few hundred meters above sea level. A theoretical fluid
model, suggested partly by laboratory experiments, includes an ocean of specified depth.
The resulting continents are tabular (that is, their elevation view is rectangular). The
surface lies above sea level, contributing to a well-known double maximum in Earth’s
elevation corresponding to continents and ocean basins. Next, a simple hydrostatic
balance between continent and ocean gives average depth and area of present oceans and
continents within 33%. Further calculations with a suitable correction to fit present Earth
cover a wide range of possible crust volumes for earlier Earth. With the present water
volume, ocean area always exceeds 25% of the globe. For all possible water volumes,
average continental crust thickness always exceeds 23.4 km. This may explain why
cratons have thicknesses comparable to younger crust so that they are found on Earth’s
surface today. Therefore, mountain building, and erosion have enabled water to carve its
own cistern in the form of the accumulated ocean basins. The wide range of areas and
depths of oceans and continents found here can constrain models of early earth. Similar
calculations can be done for earthlike planets as well.
Description
© The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 467 (2017): 18-29, doi:10.1016/j.epsl.2017.03.017.
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Suggested Citation
Preprint: Whitehead, John A., "Dimensions of continents and oceans – water has carved a perfect cistern", 2017-03-26, https://doi.org/10.1016/j.epsl.2017.03.017, https://hdl.handle.net/1912/9028Related items
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