(Reuters) - The Mississippi River was closed to traffic at two locations on Thursday as barge tows ran aground near Greenville, Arkansas, and La Crosse, Wisconsin, due to low water amid the worst U.S. drought in 56 years, private and government sources said. It was unclear when the key shipping waterway might be reopened to commercial traffic, they said. Low water has restricted barge drafts to a lighter-than-normal nine feet and limited barge tows to fewer barges on numerous sections of the Mississippi River. But even as vessels have lightened their cargo loads, numerous boats have run aground in recent weeks, forcing temporary river closures and snarling north- and southbound freight traffic. The river is a major shipping lane for grains, oilseeds, fertilizer, salt, coal, and other cargo.

SINGAPORE/MILAN, Aug 1 (Reuters) - Corn and soybean futures eased on Wednesday, as markets took a breather from a scorching rally that saw corn post its biggest two-month gain since the U.S. drought of 1988. Wheat futures lost traction after a Russian government source said the key global supplier is set to maintain its exportable wheat surplus. Even as prices drew back, alarm grew over the worst U.S. Midwest drought in more than half a century as a top agriculture company warned that the government must act fast to cut the amount of corn going to ethanol to prevent a sharp spike in food prices. Chicago Board of Trade new-crop December corn fell 1.15 percent to $7.96 a bushel by 1017 GMT, while actively traded November soy eased 0.37 percent to $16.35 a bushel. Corn and wheat prices have risen about 50 percent in the last six weeks and soybeans by around 20 percent as U.S. crops got scorched by heat and drought. Analysts said bullish sentiment was still firmly intact. "The concern about crop yields is continuing to support the market and there are reports that suggest we might see much lower yields," said Abah Ofon, an analyst at Standard Chartered Bank in Singapore.

VICKSBURG, Miss. (USA TODAY) — The Mississippi River here dropped to a daily record low Wednesday, dipping below a foot at the gauge. Though the level on the Vicksburg gauge bobbed to as low as 0.95 feet various times throughout the day, the channel, though narrowing, remains at least 9 feet or deeper throughout the system. The official level likely will be recorded at 1.1 feet. "It looks like a coastline out there," said Reynold Minsky, president of the 5th Louisiana Levee District board. "There are more beaches on the river than there are in Florida." The previous record low on the Vicksburg gauge for Aug. 1 was 2.8 feet set in 1988, said Drew Smith, a hydraulic engineer for the U.S. Army Corps of Engineers' Vicksburg District. The all-time record low was minus 1.6 feet set on July 13, 1988.

It is difficult to foresee exactly how global warming will effect Earth's many complex systems, but most of those systems are integrated. For example, glacial ice puts a large amount of pressure on the land. Release of this pressure may in fact lead to increased plate movement as the buoyant continents quickly rebound, causing increased earthquake conditions.