U.S. and European stocks tumbled on Monday over fears that Europe’s debt crisis will continue to expand.

The Dow Jones Industrial Average fell around one percent to close at 12-thousand-381-point-26 and the Nasdaq composite index fell one-and-a-half percent to two-thousand-758-point-nine.

Concerns over Europe’s debt crisis grew sharply after Standard and Poor's said Saturday that it was revising downward its rating outlook for Italy. News that the Fitch ratings agency downgraded Belgium’s credit rating caused markets to further drop.

With the eruption of Iceland's Grimsvotn volcano, European stocks saw greater drops of around two percent.

Global oil prices also slid sharply on Monday among concerns that Europe’s debt crisis would lead to a drop in demand for oil.