Two prices, one trigger
Every collateralized on-chain position — loans, perps, synths — is marked against an oracle feed, and liquidation fires on that mark. In calm tape the oracle tracks the market closely. In fast tape, update cadence, venue weighting and latency open a gap — and the gap is binding: you are liquidated at the oracle’s number even when better prices exist everywhere.
Where cascades come from
Liquidations sell collateral, selling moves the venues the oracle reads, the next mark liquidates the next tier — the on-chain version of the cascade mechanism, with the oracle as the transmission belt. Thin venues in the feed’s basket amplify it: pressure on one book can walk the mark down faster than the wide market falls.
Why manipulation targets the mark
If moving a thin constituent venue moves the mark, an attacker can spend a little on the input to force a lot at the output — the classic oracle-manipulation exploit shape. Designs like first-party feeds, medianization and time-weighting exist precisely to make that spend uneconomical; a protocol’s oracle choice is a solvency parameter, not a plumbing detail.
Reading it
Know which feed marks any position you hold, its cadence, and its thinnest constituent. In fast tape, watch the mark, not the mid — the cascade starts where the trigger lives.