Ahh, a belt sander! That makes sense. Thank you!

Before you touch the counter with a belt sander try it out on something else. In my experience a belt sander in the hands of a professional isn't precise enough for a job like this. In the hands of a novice it's recipie for disaster. I suggest hauling it to somewhere that does have a planer or drum sander. If I had no choice but do it without proper machinery,I'd use a cabinet scraper. Don't let this discourge you from future projects,it's near impossible to glue that up without mis-alighnment.

A belt sander is difficult to control. I'd first try a cabinet scraper https://www.rockler.com/cabinet-scraper-set that might just take that ridge off.

A belt sander is essential in getting the two sides on the same plane. Novices get into trouble with using too light, not too aggressive, a grit. Yes, you can sand against the grain. Practice if you have to, but this is the way this job should be done.

What else can I say Holly,Joe has Pro beside his name. Since he's adamant plus consider's a belt sander to be essential,I am defering to his judgement on this one. I don't often think it's worth begging on this forum but in this case I believe it worth begging. If you don't own a sander,they are inexpensive to rent and 60 grit belts are cheap. My plea is that you come back here to report the results. Everyone that has posted to this thread will recieve notification any time another post is made. The need to smooth out imprefections is something woodworkers have to deal with all the time so you will be doing other woodworkers a service by posting your results. I thank you for helping some of us expand on our knowledge.

I wish I could solve the debate, but I used neither a belt sander nor a cabinet scraper. I did go out and buy a belt sander last night, but when I got to work this afternoon I decided to start with my random orbit sander to get off some of the glue so it wouldn't gum up the belt sander. I was super surprised when it started wearing down that ridge, so I just kept at it and the ridge was gone in no time. After sanding the entire counter with 80, 120, 220, and then 320 you can't even see the seam. It looks just like it was part of the original glued pieces of the butcher block. I think the belt sander would have worked fine, and it would have been quicker, but hey, the orbital did the job and I'm thrilled with the results.

My husband did end up using the belt sander for one of the edges to sand down some blade marks and burns. It worked like a charm, so I'm definitely glad we added this to our tool collection.

Thanks for letting us know how you solved it,I'm sure others will find it helpful.

Holly:

You haven't said what type of finish you'll have. If it's oil, you'll probably be fine, however, any type of gloss finish will appear wavy because the seam probably wasn't flattened before it was made flush.

I'm using an oil stain, no gloss.