Causes of the Great Depression
Second, there are the monetarists, who believe that the Great Depression started as an ordinary recession, but that significant policy mistakes by monetary authorities (especially the Federal Reserve) caused a shrinking of the money supply which greatly exacerbated the economic situation, causing a recession to descend into the Great Depression. Related to this explanation are those who point to debt deflation causing those who borrow to owe ever more in real terms.
Timeline of the Great Depression
A true understanding of the Great Depression requires not only knowledge of the U.S. monetary system but also the implications of the gold standard on its participatory nations. The gold standard made the involved nations interdependent on each other's policies. Due to a fixed exchange rate, the only way to affect the demand for gold was through interest rates. For example, if interest rates were high in one country, then investors would have no reason to exchange currency for gold and the gold reserves would remain stable. However, if interest rates were low in a different country then its investors would elect to move their funds abroad where interest rates were higher. In order to stop this from happening, each nation within the gold standard union had no choice but to raise its interest rates in correspondence with its fellow nation. This interconnectivity of deflationary policy amongst so many nations resulted in the prolongation of the greatest economic downturn.