NEW YORK — U.S. stocks jumped Friday in another manic day on Wall Street, while the falling value of the U.S. dollar and other swings in financial markets suggested fear is still high about escalations in President Donald Trump’s trade war with China.

The S&P 500 rallied 1.8%, after veering repeatedly between gains and losses, to cap a chaotic and historic week full of monstrous swings. The Dow Jones Industrial Average went from an early loss of nearly 340 points to a gain of 810 before settling at a rise of 619 points, or 1.6%, while the Nasdaq composite jumped 2.1%.

Stocks kicked higher as pressure eased a bit from within the U.S. bond market. It’s typically the more boring corner of Wall Street, but it’s been flashing serious enough signals of worry this week that it’s demanded investors’ and Trump’s attention.

The yield on the 10-year Treasury topped 4.58% in the morning, up from 4.01% a week ago. That’s a major move for a market that typically measures things in hundredths of a percentage point. Such jumps can drive up rates for mortgages and other loans going to U.S. households and businesses, which would slow the economy, and they can indicate stress in the financial system.

But Treasury yields eased back as the afternoon progressed, and the 10-year yield regressed to 4.48%. That’s still higher than the day before, but not by as eye-wateringly much.

Susan Collins, president of the Federal Reserve Bank of Boston, told the Financial Times that the Fed “would absolutely be prepared” if markets become disorderly and “does have tools to address concerns about market functioning or liquidity should they arise.”

Several reasons could be behind this week’s jump in U.S. Treasury yields, which is unusual because yields typically fall when fear is high. Investors outside the United States could be selling their U.S. bonds because of the trade war, and hedge funds could be selling whatever’s available in order to raise cash to cover other losses. More worryingly, doubts may be rising about the United States’ reputation as the world’s safest place to keep cash because of Trump’s frenetic, on-and-off tariff actions.

The value of the U.S. dollar also fell again Friday against everything from the euro to the Japanese yen to the Canadian dollar.

That’s even though gold, another place where investors have instinctually flocked when fear is high, rose to bolster its reputation as a safer haven.

The shaky trading came after China announced Friday that it was boosting its tariffs on U.S. products to 125% in the latest tit-for-tat increase following Trump’s escalations on imports from China.

The repeated U.S. tariff increases “on China has become a numbers game, which has no practical economic significance, and will become a joke in the history of the world economy,” a Finance Ministry spokesman said in a statement announcing the new tariffs. “However, if the US insists on continuing to substantially infringe on China’s interests, China will resolutely counter and fight to the end.”

Rising tensions between the world’s two largest economies could cause widespread damage and a possible global recession, even after Trump recently announced a 90-day pause on some of his tariffs for other countries, except for China.

All the uncertainty caused by the trade war is eroding confidence among U.S. shoppers, which could affect their spending and translate into damage for the economy, which came into this year running at a solid rate.

A preliminary survey by the University of Michigan suggested sentiment among U.S. consumers is falling even more sharply than economists expected. “This decline was, like the last month’s, pervasive and unanimous across age, income, education, geographic region, and political affiliation,” according to the survey’s director, Joanne Hsu.