When you have fiat money, which depends on an ever expanding credit bubble, a credit contraction is the end of the fuse.
Watch out, a big BOOM is coming!!!
A classic answer is Warfare, or
Societal Collapse, or perhaps
Lunatic release of Bioweapon (SmallPox?)
I do not see a path that is not catastrophic...
One possible intermediate catastrophe would be
Abandonment of Social Security, Medicare, and Medicaid
But the number of deaths in the US alone
would be an integer multiple of 10,000,000
Hospitals, Health Care, Nursing Homes, etc. would collapse
The degree of suffering will be egregious...
-~~Ludwig Von Mises
Several brokerage houses tumbled; blue-sky investment companies formed during the happy bull market days went to smash, disclosing miserable tales of rascality; over a thousand banks caved in during 1930, as a result of marking down both of real estate and of securities; and in December occurred the largest bank failure in American financial history, the fall of the ill-named Bank of the United States in New York.
~~"Only Yesterday: An Informal History of the 1920s" by Fredrick Lewis Allen