$100M in BTC is... ~29,000BTC. Let's call it 30,000BTC.

GDAX seems to handle 5k-10kBTC on a normal day. So liquidating in a month would be 10-20% of the trading volume on GDAX, every day for a month. Even pushing it out to 3 months liquidating, it would be a sizable portion of the sales. (This would be 0.250BTC/min for 90 days.)

I, too, would like to see what happened if someone liquidated a position that quickly.

(Of course, if you had $100M in BTC, you'd probably want to liquidate over the course of a year -- where you'd still be sizable traffic, but perhaps not completely crash the price. This would be 0.06BTC/min for a year.)

Edit:

Looking closer, GDAX seems to have a volume of about 6BTC/min. So the volume estimates for clearing 30kBTC in X days:

     30 days - 11.5%
     90 days -  3.8%
    365 days -  0.95%

GDAX is about 10% of the BTC volume globally, so you're talking 0.1%-1.2% of BTC volume being that clearing, for between a month and a year.