The earth's magnetic field changes over time and this causes changes in the direction of magnetization of magnetic elements or minerals in rocks.
Our magnetic field is widely believed to originate from activities within the outer core where molten iron and nickel moves. The flow of these molten elements results in the production of the magnetic signatures on earth surface.
Some elements and minerals within rocks are capable of recording the direction of magnetic fields at a period in time. Before magma cools, such minerals in these rocks aligns their poles to that of the prevailing direction of the earths magnetic field. This is how the magnetic changes at the mid-oceanic ridges are recorded.
The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point on the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be directly overhead. Its northern equivalent is the Tropic of Cancer.
Yes, stencil one overlaps exactly with the original image. The original pattern is now hidden behind stencil one. Each point on stencil one corresponds with a point on the original image.
