How are Sedimentary Layers laid down?

You have to remember this process has variations. In some cases water is the method by whuch the layer is set, then the water shifts due to several possible reasons ie. Evaporation, river course change, ground uplift ect. Then water returns laying down a new layer meanwhile there was a period when the previous layer was exposed creating thin band of weathered material and hardening.

Fil most pretty slowly

Thanks for the response! I had in mind this kind of layering:

http://imgur.com/28eTbpK

What you said about water laying down each layer would make sense, but If water set each of these layers one at a time, does this mean that each layer was once the surface of the earth for a period of time? With plants and animals roaming over them?

In some places yes. But there are other methods of placement. Another example is near plate boundries the crust gets buckled and mountains form. Over time these mountains errode from wind and rain causing this silt to accumalate down hill.

The Earth also gains five tons of material daily. From space dust, meteors and other debris. Over thousands of years this becomes a lot of new material.

Land masses shift a lot over time. We have found ancient sea shells on the top of Mt. Everest because that ground was once under the ocean. Sea life died depositing shells which later got pushed up from plate buckling.

Water, wind, floods, rain, earthquakes, landslides all contribute to the distribution of layers.

I kind of recall that if it's deposited by wind, it's called loess, while sediment comes from water. Could be wrong about this as I didn't recheck my opinion.

How mountains form is another mystery for me, I've seen a mountain called Mount Romania, which looks like a square block:

http://imgur.com/DdizlYZ

Geology is weird, I don't think plates buckling caused a right angle around the edge of Romania though. But that's a different subject.

Silt falling off a mountain might be able to form one layer, maybe it's interrupted by local floods as time passes? There does seem to be an absence of dirt though, the kind of dirt commonly found on the surface of the ground.

And If plants and trees were growing in these layers before they turned to rock, and animals were roaming around on them before the next layer was laid down, why are there no trees or anything of the sort, where did everything go?

Fil we might suppose the plant material disintegrates while the humanoid leaves bones

That's true, there doesn't appear to be any layer of broken down plants and trees though, whihc might turn into some kind of dirt as they break down, this image here:

http://imgur.com/9e3C7hn

Red chalk I think, topped by white chalk. One material stops another starts, no sign of anything in between. This one is on a beach, so maybe not too many trees there although you can see the grass on top. In any case this seems to be the norm, one layer of one type of material, then an instant stop, with no dirt or anything before the next layer of is laid down, which will usually be one type of material as well, like the chalk layers above.

I've been watching people try to explain this to layman like me in you-tube videos, They'll do a demonstration of how layers are made and take a bucket or a bag of one kind of material and pour it out, then take another bag of a different material, pour it out and say: "Over time a new layer appears"

But no one is pouring out these layers in nature. I would of thought there might be a gradual change of material instead of this instant switch we see.

Fil I've heard this explained as a "layer" that being more soluble, simply washes away


....sure, leaving just lots of additional q's

The difficulty in explaining this process is the underline details take a lot of time to explain and how everything relates. So they skip over the details.

Okay lets take your two layer example. Red layer, white layer with nothing between.

The red layer is probably mostly clay. This layer was probably laid down by a good amount of water which changed its course. See here is where I would have to skip the details. Why? Because how does water change its course? It depends on what kind of water, ie. River, lake, ocean inlet, seaside, ect. Each type have slightly different reasons why they change over time.

So red layer was distributing a clay deposit for many years, then the water source changed. Happens a lot with rivers, they tend to "cut" new paths over time.

This new layer of white is caused by the water source tearing into a different rock deposit. When the water returns it sets this new layer down because the material being broken down by the water is different. The clay deposit is no longer supplying material due to water course change.

However; the water course could shift back to the clay deposit. Causing a flip flop effect in the layers, ie. Red, white, red, white, red.

Okay now why no in between material? The rock was not exposed long enough for plants to grow on it until "now" when the layer was obviously pushed up from plate buckling. The grass grew on top is recent, no plant material deeper because it was not exposed long enough to allow it.

Here is an explanation on river course change.



Keep in mind this process can take place over thousands of feet or even miles.

A bend in a river water flows the fastest. This tears material from the bank in the turn. Over time this causes the turn to become more and more curved until the river is like a snake.

Eventually two turns cut into each other and the river has changed its course.

At first, I thought you had written lawyers and I thought I might talk about the proper application of cement. When I read the context, I think you should consider compression force. The size of grains would be an important factor in the compression of sediment over millennia. I also think that you should consider today, but it seems you always have your head buried in the sand. Just a couple laughs for you Filbert. Good Day, Candlelight8

I had been away for a few days so I couldn't reply, wanted to say thanks for your responses everyone. Some of my questions have been answered.