I'd start by differentiating between October 29 and the start of the Depression. They're obviously related, but two very different things. And crucially they didn't happen in that order.

As for Black Tuesday and the week that culminated in it, bloated stock prices are indeed key to the scale of the collapse. But so is the already deteriorating business climate, and the unstable credit structure that sustained the speculation.

The causes of the Depression are far wider and more complex. The US had entered recession months earlier, and the international economic climate was also deteriorating. In fact if I were feeling provocative I might argue that the Crash didn't cause the slump, the earlier share boom did.

1929 was a year of commodity gluts and falling prices, which undermined confidence. But there were also monetary problems associated with Europe's return to the the Gold Standard, on top of chronic commercial weakness following the war.

To this day there's no agreed explanation despite countless books, theses and papers on the various aspects of the crisis. But you might wish to clarify which element of the catastrophe you're most interested in.