Dow Jones Crash today: U.S. stocks plunged as Trump threatened tariffs over Greenland acquisition. Dow fell 725 points, S&P 500 dropped 1.3%, Nasdaq slid 1.5%. Treasury yields surged, dollar weakened. European leaders warned of countermeasures. Nvidia, AMD, Alphabet led tech losses. Geopolitical tensions in Iran and Israel added stress. Investors fled to gold and bonds. Global markets remain volatile and cautious.