What is crashing is . . .

"the paper edifice set up as 'insurance' against default, meant to insulate the issuer against risk, and which then was turned into a profit center for larger institutions. Somebody owes somebody for every default; and that somebody is then owed by somebody, and so forth and so on down the line. The market in these things is opaque: no one knows who has what potential liabilities; in a number of cases, even the chiefs of firms involved probably do know the real exposure of their own companies. No one knows what someone might be called upon to settle up immediately; no one knows what financial firm can be relied on to make a payment tomorrow, or next Monday. The sum total of these various paper obligations is several times the total amount of real money on earth: the truth is that they cannot really be liquidated, certainly not all at once, which means that their purported value is merely an elegantly engraved fiction. When the market in them functions they are not usually liquidated, they are simply matched against one other and cancel one another out. But doing so requires their being taken at face value, or a regularized rate of discount, and maintaining them in this state requires ready access to credit for those holding them."

(Thanks, Magistrate!)