There's a news story that is making the rounds again for some reason. It concerns an academic (from Texas) who took one vial (ONE!) of sand from Omaha Beach, analyzed it, and decided that 4% of the entire beach is magnetic metal material from the invasion. Someone please beat my head until it stops hurting.
First: scientifically taking ONE vial from one place and looking at it tells you essentially nothing. There are any number of reasons why that vial could have more, or less, metal material than elsewhere on the beach.
Historically: What metal was flung into the area on D-day? Brass and lead from small arms fire don’t count as they are not magnetic (and would still be a pretty small amount). The bombs supposedly dropped inland, so did most of the naval shelling. So you've got the German mortars, bits of exploded boats and tanks and jeeps and other wreckage. Keep in mind the actual fighting there only lasted for a day. That's not a lot of shelling. As there is the low area between the beach and the bluff, little from the high ground would probably make it to the beach.
There is, however, all the junk from the blockships and the big storm. They would give off some particles, but as we've seen a lot of the big metal things are still somewhat intact. So you have to have that material move in from the deeper water onto the b each. This can happen, but then you expand the size of the area that the metal must be distributed in.
So you have a two mile long beach, and then due to currents you have to extend that out a ways on either side, and then bring that area a ways out into the sea. That is a massive region that, in theory, to have an evenly distributed 4% component. Now add in how deep does it go into the sand, and you have a staggering volume, of which 4% then has to be metal bits. How many 75mm shells, 81mm mortars, webbing bits, vehicle fenders, helmets, boot grommets, cases of c rations dropped overboard, etc. would it take to fill that volume? Then add in that a great percentage of what was originally there has oxidized to the point of being way too tiny to count. Is there enough metal there to even begin to make up 4% of the beach?
Now, if this is true, why is this phenomenon not been noticed elsewhere, like at Pacific beaches which were pounded for days, or smaller beaches where a ship broke up offshore? What about places like Verdun or the Somme where ton after ton of steel rained down on it day after day? Shouldn’t the ground be red with rust?
So the next time you are at Omaha, drag a magnet along behind you in the sand. If they are correct, it should soon become covered in rusty particles. Then look at that beach and think about just how much steel it would take to "magnetize" the sand.
The real mystery is how the University of Texas permitted this story to come out.