Hoover's interest in radio next turned him to the field of exploration geophysics, and the use of radio to prospect for oil.

Petroleum and mineral companies are prospecting for oil, gas and diamonds in a land exposed by retreating glaciers.

Prospects for oil, gold and coal received brief attention, then died out by 1912.

That same year he retired from the practice of medicine to look after his other interests, which included the lumber company (which he sold in 1914) and prospecting for oil.