Checking in on my wood (just to admire it I suppose) I noticed after the first day that a crack was appearing through the center of the log.

A through-the-centre crack, also a from-the-centre crack, is referred to as a heart shake.

I thought it was odd but wasn't really surprised as that is supposed to happen over time.

Actually it can be almost completely avoided.

When you take green wood, i.e. wood from a tree that was alive when it was cut down, and you don't want to use it straight away the end grain should be sealed ASAP to prevent/minimise cracking due to fast moisture loss.

The best way to seal the end grain if you don't want to use one of the (expensive) commercial sealers is using melted wax. Any candle wax, sealing wax or plain old beeswax will work about equally. Note: online it is frequently suggested that a thick coating of 'latex' paint (UK: emulsion) will do for this job but as a rule this type of paint is actually a terrible moisture seal. Wax is many times more effective.

When you don't seal end grain you virtually guarantee some type of cracking on wood of any real size. If you seal end grain properly however you can reduce it by up to 95%; this is on average, sometimes you'll get lucky and no cracks at all will form.

It has now been a week and and went to take another look and I was surprised this time to see a lot of radial checking? (I don't know if it has a real term.)

These are checks, cracks that form along the radius of the log. This is probably the most common type of cracking.

Note that it doesn't have to form when the wood is still a log, even after a board has been separated from the log a radial crack is still a check.

Checking in on my wood (just to admire it I suppose) I noticed after the first day that a crack was appearing through the center of the log.

A through-the-centre crack, also a from-the-centre crack, is referred to as a heart shake.

I thought it was odd but wasn't really surprised as that is supposed to happen over time.

Actually it can be almost completely avoided.

When you take green wood, i.e. wood from a tree that was alive when it was cut down, and you don't want to use it straight away the end grain should be sealed ASAP to prevent/minimise cracking due to fast moisture loss.

The best way to seal the end grain if you don't want to use one of the (expensive) commercial sealers is using melted wax. Any candle wax, canning wax or plain old beeswax will work about equally. Note: online it is frequently suggested that a thick coating of 'latex' paint (UK: emulsion) will do for this job but as a rule this type of paint is actually a terrible moisture seal. Wax is many times more effective.

When you don't seal end grain you virtually guarantee some type of cracking on wood of any real size. If you seal end grain properly however you can reduce it by up to 95%; this is on average, sometimes you'll get lucky and no cracks at all will form.

It has now been a week and and went to take another look and I was surprised this time to see a lot of radial checking? (I don't know if it has a real term.)

These are checks, cracks that form along the radius of the log. This is probably the most common type of cracking.

Note that it doesn't have to form when the wood is still a log, even after a board has been separated from the log a radial crack is still a check.