Watch Art Cashin: What's driving today's 'melt-up'

Cashin says market's melt-up no stampede

Art Cashin said Monday's stock rally was sparked by relief last week's options expirations are history and then accelerated as some short-sellers pulled out of bets stocks would go down.

Cashin, UBS' director of floor operations at the NYSE, told CNBC's Bob Pisani around midday, "A lot of people might have been nervous about volatility last week. It's gone. It's not going to threaten anymore. They began buying and then it fed on itself. Once we reached nominal new highs you could see that they kind of doubled up. It accelerated from there."

He points out that it's not a "wild rash" of buying but volume is a little bit better than recently. "It's not a stampede, that's for sure."

Cashin said Thursday's scheduled testimony by Federal Reserve chair Janet Yellen will probably be the next major event on the calendar that could move the market.