Curriculum·R402 Margin and Liquidation Mathematics·about 33 min
Cascade dynamics
By the end of this lesson you can
- →Describe the feedback loop that turns one forced sale into the next
- →Compute the condition under which a cascade diverges rather than damps
- →Explain why the same open interest is dangerous at the weekend and not on a Tuesday
- →Name the three things that actually stop a cascade
Senior · enrolled learners
This lesson opens with The weekend cascade, 4 December 2021.
- What happened
- Over the weekend of 4 December 2021 bitcoin fell sharply, reaching about $42,000 before stabilising near $49,000. About 58,202 BTC of positions were liquidated on the day, the second largest quantity recorded at the time behind 19 May 2021's 79,244. Open interest across futures fell from about $20.9B to about $16.6B in a single day, a decline of roughly 20.5 percent. No exchange failed, no oracle was wrong and no single participant caused it. Forced sales moved the price, the price reached the next band of liquidation levels, and those produced more forced sales, into a book that was thinner than it would have been on a weekday.
- The decision point
- The move was not caused by anybody deciding to sell at $42,000. It was caused by positions that had already been opened at prices where they would be closed automatically, into a market whose capacity to absorb them was lower than usual because it was a weekend. Both quantities were observable in advance. Open interest is published continuously and depth is measurable at any moment, and their ratio is what decides whether a first sale damps or compounds.
What you will be able to answer
- →What is the cascade loop?
- →When does it diverge?
- →Why does the weekend matter?
- →What stops a cascade?
Orientation and Year One are open: anyone can read them without an account. From Year Two onward the lessons are for enrolled learners, because progress through the later years only means anything if it is tracked against a record.
It is free. We do not sell the list and there is nothing to buy at the end of it.
Sources and review
- https://beincrypto.com/is-this-the-last-bitcoin-btc-shakeout-before-the-upside/
- https://coinmetrics.substack.com/p/coin-metrics-state-of-the-network-bf8
- https://www.bitmex.com/blog/how-we-are-responding-to-last-weeks-ddos-attacks
- https://finance.yahoo.com/news/over-800-000-crypto-traders-180000565.html
Confidence medium·Volatility medium·Reviewed 2026-08-07·Owner unassigned
Contested
Liquidation quantities and open interest figures for 4 December 2021 come from aggregators whose venue coverage and reporting conventions differ, and several venues publish only one liquidation record per second, which understates totals. The open interest decline from about $20.9B to $16.6B is the more reliable of the figures used here because it is a stock rather than a flow.
The divergence model in part two is a deliberately simple two-parameter model, stated with its assumptions on the page. Real books refill, market makers step in and out, and liquidation levels are not uniformly distributed. The model is there to show why the condition is a ratio rather than a level, and that conclusion is robust to the simplification.
S201-05 owns continuous markets and the behavior of weekend and overnight liquidity. This lesson uses that property as an input to the cascade condition. Keep the split and do not re-derive the 24/7 argument here.