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Tom Mazanec
2018-Nov-07, 06:16 PM
I read once that billions of years ago the only land was the island continent of Vaalbara.
If so, does that mean the Earth’s land area is increasing?

Strange
2018-Nov-07, 06:27 PM
These are normally described as supercontinents: https://en.wikipedia.org/wiki/Supercontinent

They contain all the landmasses "pushed together". I don't know if the total land area has changed much, though.

Spacedude
2018-Nov-07, 10:10 PM
As sea levels rise I suspect they'll be getting smaller.

Swift
2018-Nov-07, 10:26 PM
From the University of Puerto Rico (http://phl.upr.edu/library/notes/distributionoflandmassesofthepaleo-earth)


Table 1. Distribution of land areas of Earth in the last 750 million years. The global land coverage varied little within 10 to 30%, however, there where large transitions from South to North (Late Triassic, 220 Mya) and from East to West (Early Devonian, 400 Mya). Also, note the extreme clustering of over 95% of the land areas in one side of the planet (MFA) during Pangea (Middle Triassic, 240 Mya) and Rodinia (Precambrian, 750 Mya).

The table gives the percent land mass and ocean over time, as well as distribution, such as between the northern hemisphere and the southern.

geonuc
2018-Nov-08, 12:48 AM
From the perspective of the amount of continental crust vs oceanic crust, I would think the continents are getting bigger. Continental crust does not readily subduct so once formed, it tends to hang around. The oceanic crust gets recycled. Meanwhile, volcanic arcs are producing more continental crust. However, sea-level variation tends to flood or expose continents, and I think that accounts for the numbers in Swift's link above.

Noclevername
2018-Nov-08, 03:44 AM
Continental crust erodes faster, doesn't it?

Copernicus
2018-Nov-08, 12:27 PM
From the University of Puerto Rico (http://phl.upr.edu/library/notes/distributionoflandmassesofthepaleo-earth)



The table gives the percent land mass and ocean over time, as well as distribution, such as between the northern hemisphere and the southern.

Surprising that 10 to 30 percent is called little. If we lost 5 percent of Florida, I would call that significant.

geonuc
2018-Nov-08, 03:32 PM
Continental crust erodes faster, doesn't it?

Quite a bit faster. But the sediment that reaches the ocean forms the continental shelves, which are still part of the continental crust and not susceptible to subduction.

Roger E. Moore
2018-Nov-08, 03:55 PM
I read once that billions of years ago the only land was the island continent of Vaalbara.
If so, does that mean the Earth’s land area is increasing?

I will hazard a guess that land area is not currently increasing, if by "land area" we are talking continental crustal plates. Billions of years ago the crust was being formed from solidified magma/lava, so I can see crustal plates forming up to a limit, then stopping.

So, no, except for ocean levels going up and down, no more continental crustal plate increases.

geonuc
2018-Nov-08, 04:53 PM
Here's an article that discusses continental growth. The authors suggest that the bulk of the continental crust had been formed 3 billion years ago and the rate of growth has slowed since then. It's certainly not zero, though.

http://rsta.royalsocietypublishing.org/content/376/2132/20170403