Also I forgot to post this in my comment. The "crash" was due to a massive order. GDAX's official statement said "On 21 June 2017 at 12:30pm PT, a multimillion dollar market sell was placed on the GDAX ETH-USD order book. This resulted in orders being filled from $317.81 to $224.48, translating into a book slippage of 29.4%. This slippage started a cascade of approximately 800 stop loss orders and margin funding liquidations, causing ETH to temporarily trade as low as $0.10."