explain why fossils are commonly found in sedimentary layers?
80631
I am not sure I understand your question so I will answer it two ways. Fossils are found in sedimentary rock because they originate as living organisms, and their remains will be carried away or buried by the same processes that create sedimentary rocks. Windblown sand will build and move sand dunes, moving water will transport sediment, gravity will cause piles of rock to build up at the base of mountains, and all sorts of sediment and remains will settle to the bottom of the sea. All are possible sedimentary rocks. Since igneous rocks were once melted, and metamorphic rocks undergo chemical changes from heat and pressure, it is not possible to find fossils in these rocks. \n\nMy second answer is how sedimentary rocks (and fossils) end up in layers. Many of the processes that move the sediment, like wind, flowing water, and some gravity driven events, only happen periodically. Storms create windstorms, heavy rainfall causes rivers to flood, and often things like heavy rain will trigger a sudden landslide. These events are distinct, and each one will create a new layer of deposits somewhere. Another way these layers are created is that rivers will often change course due to changes in flow. This will cause areas that have accumulated sand to now be covered by silt or shale when the river overflows its new channel. As the river builds a delta outward into the ocean, the part of the delta where the river first meets the ocean will deposit sand, while clays and silt are carried further out into the ocean. This will create layers of shale that are later covered by sand. Within each of these layers fossils of any organism that died while those were being deposited will be trapped, and the fossils in turn can be used to calculate the age of those deposits. Every layer of a sedimentary rock represents some event in the history of the earth. \n\nIn limestone, which has a very high content of fossils, the reason for this is that the limestone is built by the accumulation of the body parts left behind by those organisms. The fossils in limestone may not be transported at all, and instead may be in same place the organism lived (in relation to the immediate rock). Layers in limestone are more often created by rising and falling of sea level. As sea level raises many organisms that end up as limestone will die off. They will then be covered by a layer of sediment falling from the overlying water, and if sea level drops again, new organisms will begin to colonize the shallower water and build another layer of limestone.
389680
Hey, iloveicecream103, why don't YOU read a book about science, then talk to us about Genesis, if you still can.\n\nFossil layers show change over time.  The lowest layers have species the least like modern species.  As you progress up the fossil record, each layer is consistently more and more like modern organisms.  Creationists have no explanation for this.  They haven't even bothered trying.\n\nComing up the fossil record, you see forms changing over time.  Clams are preceded by animals like clams, but with their shells united.  Before mammals, mammal-like reptiles.  Before reptiles, reptile-like amphibians.  Before amphibians, amphibian-like fish.  Creationists have no explanation for this either, but they have made a few wasted efforts.\n\nThe transitions evolution expects occur.  Creationists can pretend they aren't *really* transitions, they just *look* like transitions, but that's just like a child yelling "DOES NOT" to win an argument.\n\nCreationists especially need to pretend that no transitions between humans and other apes appear.  They claim that all fossils are obviously human or obviously ape.  However, if you examine the claims of multiple creationists, you'll find they disagree on which are "obviously" which.  If it was so freaking obvious, shouldn't they be able to agree?  At least a little?  Here's a chart:\n\nhttp://www.talkorigins.org/faqs/homs/compare.html\n\nThe only thing obvious about it is that the skulls obviously cannot be considered one or the other and must be seen as transitions by any open-minded person.\n\nThe transitions that evolution doesn't want do not occur.  At no point in the fossil record do we find mammal/birds.  At no point do we find any direct transitions between amphibians and mammals.  We don't find any cat/humans either.  Any of these things, if discovered, would scrap evolutionary theory overnight.  Creationists have yet to explain why God made only species that look like they could have evolved.\n\nEven without any notion of progress or change over time in the fossil record, it's sorting would be an embarrassment to creationists.\n\nScientists respect the fossil record and accept it on its own terms.  If oak trees appear on top of tree ferns, oak trees came after tree ferns.  Creationists need to impose explanations to account for their claims that everything existed together at once, but these do not flow naturally from the evidence.  For instance, they have no explanation for why oak trees are found above tree ferns.\n\nCreationists have three explanations for fossil sorting, none of them works at all.\n\n1.  They like to claim that fossils are sorted by which species could outrun the rising floodwaters (they blame Noah’s' flood for everything they can't explain).  This would mean that moles and sloths can run faster than velociraptors, Oak trees and mangroves can run faster than velociraptors as well.  Velociraptors run at the same speed as tree ferns.  It is also useless for explaining why ichthyosaurs and dolphins are never found together.\n\n2.  They claim that different species occur in different ecological zones, thus would form in different layers.  This fails again.  Mangroves are found in the lowest ecological zone of any flowering plants, but the highest levels of the fossil record.  Oak trees are found high with mangroves, instead of low in the plains.  Tree ferns should be found with oaks.  Moles should be beneath velociraptors again, and ichthyosaurs should, again, be found with dolphins.\n\n3.  They claim that the mechanical action of the flood should sort things.  Well, it should.  Too bad such sorting doesn't look at all like what is seen.  Mangroves sink, for example.  So do waterlogged oaks.  Moles are bullet shaped and would sink faster than light-boned velociraptors.  Dolphins and ichthyosaurs should, again, be found together.\n\nCreationists have lots of explanations for fossil so
956444
the types of fossils are:\n\n1.  body fossils - fossils of the actual body or body parts of an organism, whether altered or not\n2.  trace fossils - any evidence of past life that is not a body fossil.  Examples include tracks, trails, burrows, borings, impressions, molds, casts.\n3.  pseudofossils - are things that appear to be fossils but are not.  The most deceptive of these are the lacy dendrites of manganese dioxide.  Often, inorganic rock concentrations are thought to be fossilized soft parts of various animals. \n\nto form a fossil, there are important prerequisites:  there should bequick burial & there should be a hard part or parts of the organism. the the organixm is notquickly buried, bacteria or other animals may destroy it.  if the organism dies in an anaerobic environment (absence of oxygen) the soft tissues may also be preserved.
725060
Whoa! slow down, there is fossil evidence a transition from reptiles and birds. Most famously Archeopteryx with reptilian skull, teeth, digits, claws, vertebrae, sternum, ribs, pelvis, tail, and mainly unfused bones, and a few bird traits like a wishbone, wings and feathers!! In older sediments, there are theropod dinosaurs with skeletal similarities to Archeopteryx. In younger sediments, there are several fossils with more birds-like traits, such as Sinornis and Shenzhouraptor and dozens more (wikipedia "fossil birds").\n\nFossils of scales and feathers are very very rarely preserved. Imprints of the Archeopteryx feathers are only preserved because the fossils are embedded in very rare, very fine limestone that used to be used in lithography. It is unreasonable to demand fossil evidence of a transition between scales and feathers. That said, there are several theropod fossils with feathers that have been recently discovered in a fine Chinese deposit, things like Sinosauropteryx, Caudipteryx and Beipiaosaurus.\n\nBut sure, every detail of the the transition from reptiles to birds isn't documented. Other than demanding an excessive amount of evidence, I really don't know what arguments you can use, I don't think there are any true ones. But you might find some convincing sounding ones on Creationist propaganda websites. It depends on your audience.
1095083
Stratigraphic columns give the geologic history of an area. Faults & folding give a tectonic history. By examining the types of rocks that have been deposited, intruded, folded, turned over, etc. geologists have a "relative" idea (pun intended) of the workings of the earth in the past.\n\nI spend about a week teaching my 9th grade earth science students about stratigraphy. They love figuring out strat cross-sections. For them it's like doing a puzzle.
334211
Igneous, they tell us a lot about what the age of the Earth and location of the poles.\n\nSedimentary, tell us the climate of an area and preserve fossils.\n\nMetamorphic, they look cool but are hard to tell anything from.  Their general location tells us of orogenies and faults.\n\nAll rocks are important and different geologists study different things.  Oil bearing shale is important to some geologist since if we can figure out an economical method of extraction we wouldn't be dependent on other countries for oil.\n\nGeology is like a big puzzle, and it's interesting seeing how the pieces fit together.
750283
Fossils that show intermediate characteristics are generally called transitional fossils. Transitional fossils are fossils that have characteristics that are intermediate in nature to organisms that existed both prior to it and after it. As such, transitional fossils are strongly suggestive of evolution. \n\nThere are many examples of transitional fossils in the fossil record. Examples include large-scale transitions such as from reptiles to birds (like the controversial archaeopteryx) and from reptiles to mammals, as well as more detailed transitions, such as those among the many hominids or the development of horses. The fact that, despite the rarity of fossilization, we have a wealth of transitional fossil data and that the fossil data generally conforms to the phylogenetic tree is strongly supportive of the idea of evolution
1076632
The likely hood of your ending up as a fossil is extremely rare. In 99.9999+% of cases your body will just decay. Of those .0001 percent that do fossilize only about .0001 percent of those will ever be found. Really the only reason we find any fossils at all is because the earth is so incredibly old.
437078
Flatworms (Platyhelminthes) and roundworms (Nematodes) are soft-bodied animals, and therefore they're practically absent from the fossil record, because it takes extraordinary circumstances to produce fossils of these type of organisms. \nA fossilized turbellarian found included in Baltic amber, is 40 million years old (see first reference). \nFossil nematodes are also occasionally found in amber from the Cenozoic, but there are possible possible fossils from the Middle Paleozoic (see second link).\nBut anyway, all the major animal phyla are estimated to have been present after the Cambrian explosion (570 million to 495 million years ago) (see third link).
377738
Fossils such as ancient shell fish, dinosaur remains or trilobites are best found by looking at areas where long buried sediments are being exposed through erosion.  Outcroppings along river banks are one of the best places to look, as erosion is continuous.  Going out shortly after a rainstorm is usually the best time.\n\nFor arrow heads, those have only been around for at most 10 000 years or so, and most of the ones found are much younger than that.  The best place to find those is actually in farmers fields in regions that were once inhabited by native hunters.  When farmers till the soil, it brings up the debris and items buried in the dirt, including arrow heads.
850328
First off sedimentary rock is necessary for oil and gas formation. A known anticline (hill shaped folding),  is necessary for the entrapment of the oil and gas.  The rock needs to be old enough for the oil and gas forming to occur. Your not going to find alot of oil in gas in quaternary or tertiary rock. I live in an area known as the Bradford oil field and the rock age here is mainly Devonian. \n\nMany paleoentologists are being employed these days in this field of oil exploration. A core or test sample is drilled and brought to the surface and from the fossils found a determination can be made if this is a possible site for oil. (2 cent version)
81035
Shale, a sedimentary rock, is described as carbonaceous when it is interpreted or observed to contain organic matter. Commonly the organic matter originates at as plant debris which was deposited  with mud  that  through burial (pressure and heat) hardens  into a sedimentary rock called a shale.  Carbonaceous shales are often light gray to black in color and when carefully examined with a hand lens, one can see very fine bits and pieces of plant stems and leaves (microscopic fossil plants) which make up the carbonaceous organic matter of the shale. There is economic importance attached to this carbonaceous material in that it may be an important source of natural gas or methane which occurs within the earth.
861869
The major lines of evidence are:\n1) the paleoenvironments the species lived in, as evidenced by the sedimentary rocks and other fossils\n2) analogy with related species\n3) functional morphology\n4) taphonomy and trackways\n\nThings you might look up are ammonites, trilobites etc
918967
What is usually meant by an aquifer is a given formation that contains potable water.  There are many aquifers in the world.  A formation could be made from almost any kind of sediment that is both porous and permeable.  In other words, as long as the sediment contains spaces that allows it to hold water, and those spaces are connected together which allows the water to flow.\n\nAs to where the sediments come from, there are various possible sources.  Sediment is the pieces and fragments broken from other rocks.  These other rocks can be igneous (volcanic), metamorphic or even other sediments.  Sedimentary rocks can even be laid down by chemical processes.  \n\nA sediment's orginal composition depends almost entirely on what minerals the parent rock contains.  As a sediment is buried it is compressed, de-watered and heated.  The fragments may become cemented together and turned to rock.  This process is known as diagenesis.  Some of the original mineral are lost as they are turned  to clay during this process.  In order for a rock to be an effective aquifer however, the clay content should be low, as too much clay will lead to the blocking of the passages between the pores.\n\nQuartz, the mineral that makes up common sand, is resistant to chemical alteration, so sandstone is a common (but by no means the only) aquifer rock.
548967
general characteristics of clastic sedimentary rocks:\n\nthey may...\ncontain layers\nbe dull & earthy in appearance\ncontain clastic material (small grains of rock)\ncontain fossils\nrub off easily b/t fingers\nloosely "glued" together w/ minerals such as iron oxide & calcite
696439
Index fossils should occur over a broad geographic range and a very limited time span.  If a group of fossils occurred over the broad range you mention above...they would be lousy index fossils..\n\nThe whole idea of an index fossil is that if you were to find one in the rock record that you would know it occurred at a very restricted time..this identifying that layer of rock as that particular time.  the time range you have listed above covers the entire geologic history of the world except the pre-cambrian.\nthe answer to your question is no.
178643
People have been finding dinosaur fossils for hundreds of years, probably even thousands of years. There are references to "dragon" bones found in Wucheng, Sichuan, China (written by Chang Qu) over 2,000 years ago; these were probably dinosaur fossils.\n\nMuch later, in 1676, a huge thigh bone (femur) was found in England by Reverend Plot. It was thought that the bone belonged to a "giant," but was probably from a dinosaur. A report of this find was published by R. Brookes in 1763.\n\nThe first dinosaur to be described scientifically was Megalosaurus in 1824, by William Buckland a British fossil hunter and clergyman who discovered some Megalosaurus fossils in 1819 and named the reptile in 1824. It was the first dinosaur ever described scientifically and first theropod dinosaur discovered (this is all in hindsight, because the dinosaurs had not yet been recognized as a separate taxonomic group - the word dinosaur hadn't even been invented yet).