Talk:Fossil Collecting

What Is A Fossil?

Many interesting things can be discovered, just by watching the ground as you walk. Sometimes, you'll see a half-buried stone, or a feather stuck in the mud. Your dog might dig up a turkey bone from last Thanksgiving. And if you begin to dig in the soil, you might find even more fascinating items. But could you call these items "fossils"?

The original Latin word, fossilis, simply means, "dug up" or "dug out". That could refer to anything dug up from the ground. However that is much too broad a definition for the modern meaning of the word fossil. A fossil is something that is very old. No, extremely old. The modern definition of the word goes something like this:

A fossil is the remains of an animal or plant, or other life form, or evidence of its presence, or evidence of weather, climatic or geologic conditions, preserved in the sedimentary rocks of a planet's crust, and generally older than 10,000 years.

Okay, we have a definition. Let's break it down into meaningful chunks.

"A fossil is the remains of an animal or plant..." This could mean the bones of a vertebrate animal such as a fish, or a sabertooth cat. It could also refer to the shell of an invertebrate animal, such as a clam or a brachiopod, or to the calcareous skeleton of a coral or bryozoan colony. It might refer to petrified wood, the permineralized wood of a tree, or the impression of a leaf.

"...or other life form..." This refers to creatures such as molds, algae, protists (such as the large Nummulites sp. single celled organisms found in the limestones of the Egyptian pyramids), and possibly even bacteria, such as those found in Mammoth and Mastodon carcasses frozen in the ice of Siberia.

"...or evidence of its presence..." Sometimes all you can find is the preserved footprint of a dinosaur (so you know there was one walking through the mud at some point in prehistory), or the delicate outlines of a jellyfish, or the impression of a leaf, or a tube left by a worm in the solidified mud of the sea floor.

"...or evidence of weather, climatic or geologic conditions..." We find rocks (mudstones/shales or limestones) which were originally mud sometimes with the obvious pits made by raindrops, or waves frozen in the mud, or the settled fragments of shell indicating the passage and deposition from a turbidity current along a coastline, or mud-cracks left by a drought.

"...preserved in the sedimentary rocks of a planet's crust..." There are three basic kinds of rocks: igneous; metamorphic, and sedimentary. Ingeous rocks ("fire" rocks) are formed from molten magma deep inside the earth, although they also may extrude onto the surface as volcanic lava. Igneous rocks cannot contain fossils, because their formation is simply too hot...they burn everything in their path. Weathering is the process that breaks down rocks into smaller and smaller fragments until there is only pebbles, sand and silt (dust). This happens to all rocks eventually. As the fragments are washed downhill and settle into basins, or on a lake or sea floor, they form sediments, horizontal layer by layer, which build up over time. The lowest layers are eventually compressed into Sedimentary rocks. Anything caught or trapped within the layers (beds) of sedimentary rocks could be considered a fossil, whether it be the bones or shells of an animal, a tree trunk, the muddy print of a foot or raindrops, and so on. Metamorphic (changed) rocks, are rocks which have been chemically altered by heat and pressure. So igneous rocks, such as granites may be changed by heat and pressure to gneiss, sedimentary rocks such as limestones may be altered into marble. There are other examples. While some fossil shells have been found in marble, it's very uncommon for any fossils to be found in metamorphic rocks, and if they are, their shapes are usually distorted by the heat and pressure. And we cannot limit the concept of fossils to Earth. As there is very likely life on the planets of billions of other star systems, so there must also be fossils on those other worlds as well.

"...and generally older than 10,000 years." Let's face it, Granny's great, great, great, great grandmother's silver candlesticks, dug out of the bombed out basement after World War I, simply aren't old enough evidence of humans to be considered "fossils." Neither are the relics of the Sumerian, Inca or most other "civilized" human cultures. However the hominid fossils of Olduvai Gorge in Africa are. The more recent relics of human cultures younger than about ten thousand years are the domain of "archeologists." But the fossils much older than ten thousand years, going back from the early hunter-gatherer hominids, back past the giant ground sloths, past the earliest dinosaurs, the ancient trilobites, the earliest jawless ostracoderm fishes, the filmy fossil jellyfish of Australia, and far beyond, billions of years into Earth's dim past, these are the domains of the "paleontologist."

Life of Earth goes back at least 3.4 billion years, and fossils have been found representing all of that time. However, fossils are rare. Less than one millionth of one percent of living organisms ever get fossilized. The processes which produce fossils are relatively uncommon. Consider, say a deer dies in the woods. Scavengers come in and eat as much of the meat as they can, pulling the unfortunate animal apart, the bones get scattered. Flies descend and eat what they can, while depositing digestive enzymes in and on the flesh, mold spores germinate and break down any soft materials, wind blows away the strands of fur. Eventually, nothing is left but widely scattered bones. This is obviously not conducive to fossilization of the deer.

For fossilization to occur, the creature must be rapidly buried in a manner such that it is hidden from scavengers, and away from oxygen so molds and bacteria can't break it down further. So the deer must either step into a peat bog, quicksand, a tar pit, or die in flooded stream and be washed out to sea and buried in mud by a turbidity current. How often does this kind of process happen? Rarely. After burial, other processes are required to preserve the deer as a fossil. More layers of sediment must be deposited over the remains. Groundwater carrying dissolved minerals, such as calcium carbonate, could deposit those minerals within the cell structure of the bones or the skin and fur. Pressure from overlying layers will cause compression of the body, flattening and distorting the animal's original shape. And over millions of years, these processes continue. So out of the millions of deer that may have roamed a region, perhaps only one or two get fossilized. And it is only luck that guides the paleontologist or amateur fossil collector to that particular spot where the deer fossil awaits discovery. Perhaps that lucky fossil collector will be you.


 * you know this is the discussion page, not the book page? --Rhole2001 (discuss • contribs) 02:22, 30 April 2018 (UTC)