Flooding last year may have worsened the situation on the Mississippi by leaving deposits of silt and debris in areas that would normally be clear.

CNN: STORY HIGHLIGHTS

As the outlet linking this sea to the ocean became blocked, the sea began to evaporate slowly, leaving behind the mineral and saline deposits of the so-called Salado Formation.

ECONOMIST: Old salts

Flows into bank deposits are particularly dangerous: capital can arrive or flee remarkably quickly, leaving policymakers no time to react.

ECONOMIST: Time to turn off the tap?

Well, as I've been pointing out for some weeks the big threat to banks in eurozone countries perceived to be at some risk of leaving the currency union - such as Greece, Spain, Portugal, and Italy - is an outflow of deposits.

BBC: Where to find bank stress