Geologist claim that besides the main magnetic N-S poles, there are several local poles on the earth's surface oriented in different direction . How is such a thing possible at all ?

Question

$\begin{array}{1 1} \text{due to deposition of various minerals } \\ \text{due to deposition of large deposits of iron} \\ \text{due to the deposition of magnetized minerals} \\ \text{none of the above} \end{array}$