I searched for this and I don’t think it’s been addressed in any previous Straightdope threads, and I can’t seem to find the answer on line.
I’m just currious about what terrain existed on either super continent. I’m assuming in Rodinia there was probably just mountains and plains probably?
What about the time when Pangaea came into existance, did things like forests or jungles exist? What about desserts?
If not, how long ago did the varrious terrains, forests, jungles, plains, desserts, tundra, and valleys come into existance?
Thanks.
Pangaea had an icecap centered on the South Pole at the time for a large part of its existence, which was presumably surrounded by tundra. It had all the topographic features of modern continents: Mountains, foothills, piedmont, plateaux, cuestas, deserts, rock deserts, presumably intermontane river valleys, coastal plains, fjordland, etc. Ecological features were of course different, because plant life was rapidly evolving, and neither grasses nor any angiosperms (flowering plants) had evolved during its existence. It would take a short course in paleobotany to cover what did exist, but suffice it to say that fern/cycad-type tropical “jungles” (i.e., jungles in popular parlance but not to ecologists) were present. Ground cover on plains and plateaux is purely hypothetical, but was probably comprised largely of club mosses, horsetails, ferns, and mosses and liverworts, not far different from what grows on infertile areas like cinder piles and some railway embankments today. I believe conifers came into existence towards the end of Pangaea.
Rodinia did have a large icecap as well. Any parts not icecap or tundra were barren ground, presumably with topographic features, but easily eroded, as land plants had not yet evolved.
Without plants you wouldn’t have humus – organic matter, but there would be clays and silts as these come from the break down of rocks. The soild would be very mineral, but it would lack all the stuff that organic matter provides. You’d probably not have very acidic soil, as it’s often plant acids (tannins) that acidify soils.
It is thought that a relatively large part of Pangea was arid, with a “continental” type climate, since so much of it would have been far inland and away from any coast. Think Gobi Desert or inland Australia.
That sort of thing depends very much on the relationship between rainfall and evaporation. It’s likely that Pangea at times would have had large areas of internal drainage like the Great Basin. It is more likely that such regions would have had something like the Caspian or Aral Seas, if they had much surface water at all.
Sure there would be lakes. In any area where the water doesn’t evaporate fully during the year, or gets enough input from things like rivers and streams there would be. Areas where there’s an impermeable layer are likely to hold water, or places where the land is lower than the surrounding water table as well.
Plants do alter the landscape, but they really don’t have much effect in regard to things like lakes and rivers and streams. They can cause ponds and shallow lakes to flll in (through rotting and filling the lake with organic matter, creating things like peat bogs).
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