If I may summarize the most popular answers - most people think that it is the low liquidity (available circulation) and a 24/7 non-stop trading environment that are responsible for the large volatility in Bitcoin. Of course, small market cap and price manipulation also play a part of it.
That is without a doubt a factor but another factor has to do with the fact that there are many traders that use too much leverage, in the forex markets it is rare for a trader to go above 5x in leverage while in this market people can use as much as 100x leverage regularly, this means that when the market goes against them and their positions gets closed this reduces the price significantly and a domino effect happens making the price to go down very rapidly.
Why can one get 100X leverage on Cryptocurrencies market? Do you mean by placing $100 into the investment, I can buy up to $10,000 of cryptos?