I think the best thing to do, is to get a certified arborist to come and do an inspection on the tree.
He will be able to assess the risk and the best way to deal with it.
Its possible that the split is just in the bark, which is common with euc's but best get a professional to take a look anyway.
You can't be too careful were safety is concerned!
Good Luck.
I have also noticed that a very large root has come to the surface near to the tree, but as it is growing next to a young oak tree I don't know which tree the root belongs to [if either]