The first cause of the Great Depression was the Stock Market Crash of 1929. $14,000,000,000 of investments were lost, and two months later, that had increased to $40,000,000,000. The market lost 12% of its value on "Black Tuesday".
After the Stock Market Crash, 700 banks began failing in the late months of 1929. This eventually lead up to upwards of 3,000 banks completely crashing in 1930.
There was also a reduction in purchasing across the board. Most investments were worthless now. People's savings were diminished or gone altogether. Nobody could buy much. The unemployment gradually increased to soon be above 25%. Inventory was accumulating, and nobody could stop it at the time.
The government had to do something at this point, so they passed the Tariff Act of 1930. A tariff is a tax placed on something. The act raised this tariff in trade, and world trade fell by about 2/3.
The last cause was the environmental destruction. A drought had come along due to nobody bothering to use soil-preservation strategies. This prevented farmers from making money, therefore furthering the Great Depression that much more.
