Why do I black out when I mix alcohol with marijuana?

I’m 18 and over the last year I’ve gotten cross faded on only 2 separate occasions and each time that I’ve done so I’ve blacked out. The first time was at a kickback with a group of my friends and I had started drinking pretty early into the night, and at around 3-5 beers in I had smoked some weed, I was cool for the rest of the night and continued to drink as well, then later in the night I had smoked again, this time with a RAW Joint holder that held up to 5 joints in it. My friends and I smoked the joints all at once and I took only a few good hits before I was ready to tap out. I continued to drink more throughout the night and the last thing that I remember was lying my head down, then the next morning I had woken up in the middle of a conversation that I had already been having but I wasn’t conscious to remember starting. I was thrown off and began to panic a little bit and that’s when I had realized that I had blacked out. I probably had around 18 beers or so that night and I had only drank that much one time before, but never blacked out which was what caught me off guard.

The second time I had blacked out was on New Year’s eve, I had smoked a J outside with my buddy and I had got pretty high. That night I had for sure had less alcohol than the previous time that I had got blacked out but I drank a bit faster. Full hours had been erased from my mind and the next morning I woke up with pretty mild hangover anxiety, I had a cut on my eyelid that I didn’t know the source of and I my friends had said I was being stupid the whole night just talking shit and being annoying, which isn’t anything insanely bad but it just frustrates me that it even happened because I don’t know why I black out so easily.

For some extra context, I don’t drink or smoke weed too often, I smoke more than I drink and the weed that I had smoked on New Year’s eve was infused so it had a higher THC level.