Why are dinosaurs buried so deep? Did rock form over them?
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Not all are now buried deep, although to become a fossil, at one stage they were. There are places in the world where the ground has eroded and you can see them sticking out of the ground, or poking out of cliffs. You just need to know what you are looking for to see them.
>Did rock form over them
Yes, that’s why geologists can date rocks, sediments get constantly deposited in seas / lakes / rivers / lowlands etc., and form layers one over another.
The reason we can find them is because eventually those rocks get uplifted by tectonic activity (stuff moves around) and are now hills or mountains, which start eroding instead (depositingthe sediments in seas / lakes… You get it). As those rocks erode, we can find fossils hidden in them.
As a small factor, there is also material our planet picks up from space. Estimates are that we acquire about 5200 tons of space dust per year. Multiply that by 65 million years, and that adds roughly 338 billion tons of dust. Reality is, that’s probably less than an inch or two over the whole earth, but it still adds to the erosion materials.
Did you ever find something half-buried in the ground that someone dropped/discarded? Like an old toy or a piece of metal thats all dirty? Add a few million years to that.
Wind and water.
Wind moves sand and dirt. Seas, rivers and lakes flood and leave behind a layer of dirt. Sometimes large fires or volcano eruptions lay down a layer of ash. That effect over 65 million years means they get buried quite deep. During that time, the loose layers of sand, dust and dirt also compress and petrify, becoming stone.
Of course, all that dirt and sand has to come from somewhere, so not every skeleton gets preserved. The ones that aren’t preserved eventually get worn down by the elements.
So, in short, not every dinosaur gets buried. But the deeper they’re buried, the better they’re preserved.