Thanks for your question. I don't want to speculate about the type of tree, so could you please ID it? Could you take a picture of the entire tree, to give me more information about the tree's general health? Thanks.

Unfortunately I can't remember the name. Does this picture help? 

It's a start! I'm away from my library and computer, so must await until tomorrow. Most trunk splits are a result of some weather condition, don't mean the tree is doomed, and don't need to be treated. Do not try to seal the wound, but you should monitor it for insects, mushrooms (fungus--an indication of dead tissue), or oozing. Back to you by this time tomorrow.

I can't tell from the photo whether the leaves are alternate or opposite on the stems, and I think the edges of the leaves are serrate (like a steak knife.)  But, I'm going to assume it's an alder species.  Its crown and leaves look really healthy, and I see no split in the trunk that would indicate it is a hazard.  So, just keep an eye on it, monitor as I earlier suggested, and fertilize and water regularly.  Write back if you see anything else untoward.  Good luck!