It has to be huge amount. I know the market cap is just virtual number, but still its staggering. If this happened in real world's markets, that would mean epic disaster for global economy.
You can easily ascertain market cap on CoinMarketCap for every cryptocurrency over any period.
By the way, this can never happen in real economy because estimated market caps as we measure in case of cryptocurrencies won't happen in real world. In real world, market cap is actually backed by equivalent money suppose if we say market cap of Google is $40 billion, it actually means total asset worth of Google is $40B. That is the reason why we don't see volatility as of Bitcoin in real world.