Good day. Watching an entertained TV program of people searching/picking pebble size meteorites on land surface, came to a doubt...

Would those meteorites on earth surface be 'very recent' arrivals, as old arrivals would be deeply buried in substrates that now have been covered with layers of sediments ?

Do all sedimentary layers form under water ? Also being low mass, did not penetrate to subsoil; and larger ones are always buried under eons of layers due to their energetic impact, showing like inclusions ?

-Images borrowed from the web-

1 hour ago, Externet said:

old arrivals would be deeply buried in substrates that now have been covered with layers of sediments

Uplift and erosion exposes older sediments, so it’s not necessarily the case that the surface layer is young. Where were they doing this?

Saw several episodes on free "Prime" TV; each at a different location all over the globe. Do not know how many are available 'on-line'

--> https://m.imdb.com/title/tt1487514/episodes

--> https://pluto.tv/us/on-demand/series/6227a0d24e4cae001a317f8d/season/1

--> https://tubitv.com/series/300001256/meteorite-men

Some sedimentary layers surmount while some subside according to the geology of the mantle in that location.
So I guess the answer is "It depends".

8 hours ago, Externet said:

Good day. Watching an entertained TV program of people searching/picking pebble size meteorites on land surface, came to a doubt...

Would those meteorites on earth surface be 'very recent' arrivals, as old arrivals would be deeply buried in substrates that now have been covered with layers of sediments ?

Do all sedimentary layers form under water ? Also being low mass, did not penetrate to subsoil; and larger ones are always buried under eons of layers due to their energetic impact, showing like inclusions ?

-Images borrowed from the web-

How did they determine these were meteorites? Are they iron or something?

10 hours ago, Externet said:

Saw several episodes on free "Prime" TV; each at a different location all over the globe. Do not know how many are available 'on-line'

--> https://m.imdb.com/title/tt1487514/episodes

--> https://pluto.tv/us/on-demand/series/6227a0d24e4cae001a317f8d/season/1

--> https://tubitv.com/series/300001256/meteorite-men

Most of the episode summaries on IMDB tell you where they are and how old the meteorites are. There’s probably information about how they know the age and more details if you search on the name of each meteorite field.

12 hours ago, Externet said:

Would those meteorites on earth surface be 'very recent' arrivals, as old arrivals would be deeply buried in substrates that now have been covered with layers of sediments ?

Thorsburg quarry in Sweden is pretty well-known for having yielded over 100 fossil meteorites from the Ordovician period (nearly half a billion years back).

Similar examples are quite common.

12 hours ago, Externet said:

Do all sedimentary layers form under water ?

No. Basin areas in deserts tend to consolidate pretty well without needing to be submerged. Many other examples.

4 hours ago, exchemist said:

How did they determine these were meteorites? Are they iron or something?

Tell-tale inconsistencies with the contextual setting, chemistry, and radiometric age of the surrounding country rock.

There's only so many ways that lumps of planetary mantle and core materials can arrive on the surface. Highly resistant, stable minerals such as zircon and spinel are useful markers.

1 hour ago, sethoflagos said:

Thorsburg quarry in Sweden is pretty well-known for having yielded over 100 fossil meteorites from the Ordovician period (nearly half a billion years back).

Similar examples are quite common.

No. Basin areas in deserts tend to consolidate pretty well without needing to be submerged. Many other examples.

Tell-tale inconsistencies with the contextual setting, chemistry, and radiometric age of the surrounding country rock.

There's only so many ways that lumps of planetary mantle and core materials can arrive on the surface. Highly resistant, stable minerals such as zircon and spinel are useful markers.

If these are people just picking them up, one would think there must be some visible feature or something detectable by a hand-held device like a magnet. Maybe it is just the mineralogy that indicates they are "erratics".

Yes, probed from color and appearance first, picked up by a magnet, analyzed in laboratories mostly for iron-nickel, and details of environment effects if desertic or moist; rust/deterioration/type/family/parent documented decently well in the videos. Interesting that most are visually discernible exposed on soil surface. From my understanding, meteorites explode to small pieces by atmosphere or impact spreading large areas on surfaces because their low masses being small, do not penetrate soils, being visually found by a trained eye, also metal detectors.

Why they explode in fire I cannot tell. Presence of oxygen, have temperature, but what is the fuel ?

19 minutes ago, Externet said:

Yes, probed from color and appearance first, picked up by a magnet, analyzed in laboratories mostly for iron-nickel, and details of environment effects if desertic or moist; rust/deterioration/type/family/parent documented decently well in the videos. Interesting that most are visually discernible exposed on soil surface. From my understanding, meteorites explode to small pieces by atmosphere or impact spreading large areas on surfaces because their low masses being small, do not penetrate soils, being visually found by a trained eye, also metal detectors.

Why they explode in fire I cannot tell. Presence of oxygen, have temperature, but what is the fuel ?

Thermal shock I expect, from differential heating in the atmosphere. The skin must reach thousands of C deg, while the inside is still cold from outer space.

Thanks for the explanation about how they know what to pick up.

I bought many slices of smaller as these (my favorite type) for presents along years. It is a good feeling having on your hands something that old out of this world. 😳

--> https://www.ebay.com/b/Muonionalusta/3239/bn_7023272052

-->

Next will be a pallasite :

18 minutes ago, Externet said:

Why they explode in fire I cannot tell. Presence of oxygen, have temperature, but what is the fuel ?

It's simply due to friction forces from their pretty extreme velocity encountering the thin air of the upper atmosphere. It's very much a surface effect so a car sized bolide may be losing incandescent molten material from the surface while the bulk remains at well below freezing point.

Depending on composition, the extreme temperature gradient creates enormous stresses due to differential expansion, until the internal bonding fails and successive layers of skin are blown off like the layers of an onion.

It isn't 'burning' in our normal understanding of the term.

Hope this helps, taken from the linked site.

Most space rocks smaller than a football field will break apart in Earth’s atmosphere. Traveling at tens of thousands of miles per hour, the object disintegrates as pressure exceeds the strength of the object, resulting a bright flare. Less than 5% of the original object usually makes it down to the ground.

NASA Science

Meteors and Meteorites: Facts - NASA Science

Meteoroids are space rocks that range in size from dust grains to small asteroids. This term only applies when these rocks while they are still in space.

Part of this series of DVD lectures shows Dr Stewart in Western Australia picking up meteorites amongst some of the oldest rocks on earth at the surface ie billions of years old.

This episode video is about those small ones on soil surface --> https://tubitv.com/tv-shows/200021886/s01-e07-dry-lake-bed