The last week of January 2018 and the first week of February 2018, the Dow Jones dropped several hundred points. It looks to close out February 2 down hundreds of points, with other indexes (S&P 500, NASDAQ) to follow. While this may seem like a crisis, it is more than likely to reflect short-term investors taking their profits (in the long run up to this point) and shuffling them to other types of investments to prepare for improved bond yields.
If you could only listen to one person's advice during a stock market crash, let that person be famed investor, Warren Buffett. Not only will the Berkshire Hathaway (NYSE: BRK-B) (NYSE: BRK-A) chairman and CEO's advice serve you well, but his knack for keeping a clear head -- and even getting a bit greedy (more on that later) -- when everyone else is selling, may make his the only advice you need to navigate uncertain times.
The crucial point of their paper was that sandpile avalanches could not be predicted, and not because of randomness (there was no random component in their model) or because the authors could not figure out how to come up with equations to describe it. Rather, they found it impossible in a fundamental sense to set up equations that would describe the sandpile model analytically, so there was no way to predict what the sandpile would do. The only way to observe its behavior was to set up the model in a computer and let it run.
2015–16 stock market selloff 18 August 2015 The Dow Jones fell 588 points during a two-day period, 1,300 points from August 18–21. On Monday, August 24, world stock markets were down substantially, wiping out all gains made in 2015, with interlinked drops in commodities such as oil, which hit a six-year price low, copper, and most of Asian currencies, but the Japanese yen, losing value against the United States dollar. With this plunge, an estimated ten trillion dollars had been wiped off the books on global markets since June 3.   
In 1979, Activision became the industry's first third-party developer. It was founded by Atari programmers who left the company because Atari did not allow credits to appear on their games and did not pay employees a royalty based on sales. At the time, Atari was owned by Warner Communications, and the developers felt that they should receive the same recognition that musicians, directors, and actors got from Warner's other divisions. After Activision went into business, Atari quickly sued to block sales of Activision's products, but failed to secure a restraining order and ultimately settled the case in 1982. This court case legitimized third-party development, encouraging companies such as Quaker Oats (with their US Games division) to rush to open video-game divisions, hoping to impress both stockholders and consumers.
Markets can also be stabilized by large entities purchasing massive quantities of stocks, essentially setting an example for individual traders and curbing panic selling. However, these methods are not only unproven, they may not be effective. In one famous example, the Panic of 1907, a 50 percent drop in stocks in New York set off a financial panic that threatened to bring down the financial system. J. P. Morgan, the famous financier and investor, convinced New York bankers to step in and use their personal and institutional capital to shore up markets.
Officials announced that new trading curbs, also known as circuit breakers, would be tested during a six-month trial period ending on December 10, 2010. These circuit breakers would halt trading for five minutes on any S&P 500 stock that rises or falls more than 10 percent in a five-minute period. The circuit breakers would only be installed to the 404 New York Stock Exchange listed S&P 500 stocks. The first circuit breakers were installed to only 5 of the S&P 500 companies on Friday, June 11, to experiment with the circuit breakers. The five stocks were EOG Resources, Genuine Parts, Harley Davidson, Ryder System and Zimmer Holdings. By Monday, June 14, 44 had them. By Tuesday, June 15, the number had grown to 223, and by Wednesday, June 16, all 404 companies had circuit breakers installed. On June 16, 2010, trading in the Washington Post Company's shares were halted for five minutes after it became the first stock to trigger the new circuit breakers. Three erroneous NYSE Arca trades were said to have been the cause of the share price jump.
Though we don't know what will motivate a future market crash, it's likely to be something that will ultimately be recovered from if history is any guide. The economy and society are very flexible. Industries, and even countries, can rise and fall over time, but if you have a global, well-diversified and lower cost portfolio, then you should be well-positioned. This is an area where diversification helps. If you spread your bets it will likely help. You'll probably find that the next crisis centers on a specific country, part of the globe or investment theme. If you've spread your bets through diversification, then you'll undoubtedly have some assets that fall in value, perhaps alarmingly, but often certain assets can do well during certain crises such as high-quality bonds, more defensive or inexpensive parts of the stock market, or commodities including gold.