Chris Peterson wrote:
BDanielMayfeild wrote:As I love deserts and mountains and canyons, I’ve often daydreamed about what we may someday find on some distant world; a planet with a super continent largely drained by a river system much larger than anything presently on earth. Imagine a world where a river larger than the Amazon has carved through a plateau higher than Tibet. In such a place our planet’s Grand Canyon would be a mere side canyon on a main gorge perhaps ten’s of kilometers deep ...
There are natural limits on how high mountains can get, or how deep valleys can be cut. Or more precisely, on how steep the walls of mountains and valleys can get. Consider Mars: a massive mountain in Mons Olympus, an incredible canyon in Valles Marineris. Yet if you were near either, they'd seem far less impressive than many much smaller mountains on Earth, or much shallower valleys. Because in order for these to reach their heights and depths, they also had to spread out. You wouldn't be able to identify Mons Olympus as a mountain if you were at its base, and most of Valles Marineris would seem much less deep than the Grand Canyon.
A planet with geologic structures of great height or depth but similar extent to those on Earth would be a very odd planet indeed- materially nothing like a terrestrial planet, and probably with very low gravity.
The grander than the Grand Canyon planet I was thinking of wouldn’t have to be all that much different than the earth Chris. As I’m sure you know the earth itself has had super continents several times in the past, so rivers with much larger watersheds than anything we have today could very well have existed even here.
But the canyon riddled planet I was thinking of could be, say 10% larger than the earth and if it had, say a 2% lower average density than earth due to enhanced percentages of silicates and other lighter than iron elements it’s surface gravity wouldn’t be very different than that of earth but the continental crust could be significantly thicker and of wider extent than earth’s percentage of continental to basaltic crusts. Add in an ocean covering around 60% of this hypothetical world and it would have a total surface area 4pi(1.1R(earth))^2 = 618,535,000 km^2, and the 40% land area would then be about 247,414,000 km^2, which is about 65% larger than earth’s present land area.
I don’t think that the existence such a planet is impossible, nor even, given the shear number of planets, is its existence even unlikely. Why couldn’t such a planet have an enormously deep gorge cut through a range of mountains taller that our Himalayas?
"Happy are the peaceable ... "