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This is something that has always fascinated me - just how do the processes which cover a landscape with, say, layers and layers of sediment - or jungle cover -
by mmjaa 9y ago
This is something that has always fascinated me - just how do the processes which cover a landscape with, say, layers and layers of sediment - or jungle cover - really work?
I mean, I get it - you leave something out, a few weeks later its going to get covered in a layer of dust/sediment. But how is it that entire cities get buried under 10's of meters of dirt? I'm sure geologists have this all figured out, but it always amazes me that our world changes like this so rapidly.
In this case, I'm sure the answer is 'the jungle eats everything' .. but there are places in the world, buried under meters of sand and sediment, that I just wonder .. how does this happen ..
- ch4s3 9y agoLeaf litter accumulates and breaks down and becomes new soil, mountains and hills erode and that sediment accumulates in lower areas, wind move lots of sand and fine sediment around, All of that piles up in places until things once on top of the soil are now buried. It's a little more complicated than that, but that's part of the process. Another aspect is that cities used to literally rise as they deposited waste in situ and had to build up as 1st floors became basements. This is partially the source of mounds. Neat reddit discussion: https://www.reddit.com/r/AskHistorians/comments/17je7i/archeologists_are_always_digging_up_ancient_ruins/ https://www.reddit.com/r/AskHistorians/comments/17je7i/arche...
- edgarvaldes 9y agoYeah, same here. And some ancient cities and settlements have _layers_ below them[1]. How? [1]https://en.wikipedia.org/wiki/Troy#Historical_Troy_uncovered https://en.wikipedia.org/wiki/Troy#Historical_Troy_uncovered
- maxerickson 9y agoArchaeologists have characterized various layers, the depth and thickness will vary. So a layer there might just consist of evidence of some particular activity that one settlement engaged in that earlier and later ones did not.
- deleted 9y ago[deleted]
- InclinedPlane 9y agoIt's not that complicated. Humans tend to build in flat areas. Flat areas tend to be flood plains. When flood plains flood they leave behind sediment. There are additional ways that sediment builds up such as airborne deposits and importantly from growing plants leaving behind biomatter, but in a lot of cases flooding explains the substantial depth of sediment deposited.
- mturmon 9y agoIt’s one of those overlooked facets of Nature. Much of the Great Plains sits on the Ogallala Aquifer. This is an underlying terrain, to depths of hundreds of meters, filled in by sediment from the Rockies (https://en.m.wikipedia.org/wiki/Ogallala_Aquifer#General_characteristics https://en.m.wikipedia.org/wiki/Ogallala_Aquifer#General_cha...). The greater part of the LA Basin is a floodplain which consists of hundreds of feet of sediment from the San Gabriel mountains.
- jccooper 9y agoThere are lots of depositional (and erosive) processes happening. They're all subject to local conditions. But the most common (in no particular order) are: accumulation of plant matter, flood deposits, human-generated organic and building debris, and earthworm casts. You can also see other things, like volcanic activity and wind-blown material, in fewer places.