What happens when a stablecoin depegs and how it cascades through DeFi
A stablecoin is supposed to be stable. When it breaks that promise, the damage travels fast.
The March 2023 USDC depeg is the clearest case study. Circle held $3.3 billion of its $33 billion USDC reserves at Silicon Valley Bank. On March 10, SVB collapsed. USDC dropped to $0.87 on major exchanges. The market did not wait for FDIC clarity; it priced the worst case in minutes.
That price dislocation became a chain of forced events across DeFi. Here is how the cascade works.
Oracles confirm the break.
Lending protocols like Aave and Compound rely on price feeds from Chainlink or similar oracles. During the USDC event, those oracles updated to reflect the real market price. On Aave V2, USDC slipped within three hours to a price around $0.90 against the protocol's internal peg logic. The protocol did not pause or judge. It just read the feed and updated every position that used USDC as collateral.
Health factors drop below 1.
Aave tracks a health factor for each borrower. If you deposited USDC as collateral and borrowed ETH against it, your collateral's dollar value just shrank by 10-13%. The loan size did not change, so your health factor fell. For anyone near the liquidation threshold, the fall was instantaneous and total.
On Aave, roughly $1.2 billion in USDC deposits were present across V2 and V3. Compound held around $700 million. Both protocols saw mass liquidation triggers within hours of the depeg bottom.
Liquidators execute, profit, and move on.
Liquidators are bots. They watched the oracle updates and pounced. On Aave V2 alone, liquidators repaid roughly $200 million in bad loans in the first 24 hours of the depeg, buying discounted collateral and selling it for a spread. The protocol stayed whole - this time.
But not every position could be liquidated fast enough. Some borrowers had no liquidator willing to take the trade. If the collateral asset itself was dropping alongside the stablecoin, the incentive to liquidate vanished. That is where bad debt appears.
Bad debt accumulates when liquidators sit out.
Compound experienced this directly. During the USDC event, Compound's USDC market saw a utilization spike above 90% and borrow rates surged. Yet some underwater positions remained open because the collateral - often volatile assets like ETH - was also declining. Liquidators faced a paradox: take the collateral at a discount and watch it fall further, or wait. Some waited.
Compound eventually accumulated roughly $70 million in bad debt from the USDC depeg. The protocol's treasury covered the shortfall. Not every protocol has that buffer.
Curve pools showed the warning first.
Before the oracles updated, before any loan was liquidated, the Curve 3pool signaled trouble. That pool holds DAI, USDC, and USDT in equal weight. On March 10, its balance shifted to 72% USDC and 14% each of DAI and USDT. Arbitrageurs had dumped USDC into the pool, buying DAI and USDT at a premium.
That imbalance was visible on any block explorer or dashboard. It was the earliest on-chain signal that capital was fleeing USDC. Anyone watching Curve pools saw the depeg forming before centralized exchange prices reflected it.
What does this mean for DeFi participants?
A depeg event collapses positions in minutes, not days. If you borrow against stablecoin collateral, the margin you think you have can vanish with one oracle update. Liquidation triggers are mechanical; they do not assess your intent or your belief that the peg will return.
Bad debt is not evenly distributed. Protocols with deep liquidity and fast liquidators survive. Those with concentrated collateral types or slow oracle updates absorb the loss. The USDC event was survivable because USDC eventually returned to peg. If the stablecoin had not recovered, the bad debt would have been permanent.
The pattern repeats.
Every stablecoin depeg follows roughly the same sequence: pool imbalance, oracle break, health factor collapse, liquidation wave, bad debt decision. The details change. The structure does not.
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