Read this and answer the question. If the question is unanswerable, say "unanswerable".

St. John's, and the province as a whole, was gravely affected in the 1990s by the collapse of the Northern cod fishery, which had been the driving force of the provincial economy for hundreds of years. After a decade of high unemployment rates and depopulation, the city's proximity to the Hibernia, Terra Nova and White Rose oil fields has led to an economic boom that has spurred population growth and commercial development. As a result, the St. John's area now accounts for about half of the province's economic output.

What industry caused St. John's economy to boom in the 1990's?
unanswerable