Fossils of tropical plants found on an island in the arctic ocean are evidence for the theory of

It is called CLIMATE EVIDENCE.

Climate evidence is a Fossils of tropical plants were found on spitsbergen, an island in the Arctic Ocean. When those plants were there it must have been closer to the equator. There are different kinds of fossils evidence another one is ocean evidence and puzzle evidence. 

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.