“Not saying it’s (the field) a spot phenomenon”
?
“are (measured as) a spot phenomenon”
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In parentheses are the two different contexts that those were made.
So I will repeat it again for you.
When you are sampling a location for the effects of the magnetic field in history, it is a SPOT phenomenon.
The field itself is a global phenomenon, obviously.
That’s the whole point I was trying to make. The field does not disappear no even does it potentially diminish by a major fraction in it’s global effect. However, if it is bobbing and shifting a lot over the period of time where you obtain your sample, the iron (or other sample source you are measuring) are not going to show a singular strong alignment
“However, if it is bobbing and shifting”
Contradicts your original.