You are quite correct in there was a liquidity crisis throughout the international financial system. The system was working less and less effectively over the 3-4 years prior to the crash. The Lords of Finance covers these events in detail. Nonetheless, many economists state that the triggering event for the final collapse of the economic system was the US Stock Market collapse in 1929. When US banks were forced to come up with cash to pay off their margin calls, they called in loans both in the US and abroad with the ripple effect that liquidity dried up and eventually world economies collapsed. The actions taken by the Federal Reserve and US Government only compounded the problem.
Actually, the crash
itself was not the trigger, but I
really suggest you look at 3 banks (all folded during the period afterwards, and I don't have my notes on this handy) The crash was the visible final proof of the liquidity crisis. Or more precisely: Several banks (not just European, but they triggered what came next) called in their margin calls, as well as called in notes they were owed, backed by securities, all in the few days leading up to the crash.
Or: Bank A called in Bank B's note, who called in Bank C's, who then started scrambling around for cash, calling in every liquid asset, and calling in it's short term stock loans, which triggered the sell off. Sell offs are not triggers, they're the proof
of the trigger.
Lords of Finance IIRC, even discusses this. The economists are right in a
sense, that the stock market was 'the trigger' in a
psychological sense. But a
fair amount of people (Hughes was one, oddly enough) had already cotton onto the system's going into recession. What the crash did, was make it
obvious.
To be
really cold: the Trigger for the Great depression, was how the end of WW1 came about, combined with the farming market being... shall we say, substandard.
The stock market in itself, crashing, isn't a big deal. It was going to correct, a
lot of smart people knew this, and a fair amount had begun edging themselves out. What
the stock market crash did, was catch a
lot of banks without reserves, or others with no spare capital.
The only practical way, given mores and political thought to prevent the great depression? In primus: No reparations, no war debt (which the US had actually proposed to a degree, IIRC, can't recall if it was Coolidge who suggested this, or was it Wilson, and if so, he was right to do so, maybe the
only thing he was right about...), which would have helped Austria and Germany out severely, and lessened the burden on Britain and France. Even
then, a nasty recession would have happened, period in roughly the same period, due to previous mentions of demand shock, and the farming crisis that was building.
This would have given Britain more money, and the ability to stabilize the system (to some degree) and quite possibly talk the US into helping stabilize.