Why was the expansion of colonization important for the industrial revolution in england?

Though Hobart's "tools of Empire" had been available for decades as a result of the Industrial Revolution, it was not until this period that they were used extensively, as the so-called Age of Indifference, during which Britain was a satiated power, came to a close. Between 1870 and 1900 the formal Empire expanded to occupy an area of 4 million square miles, despite the lack of coherent imperial policies. Yet there is no simple explanation as to why such expansion took place during this period, and it is only through combination of the many factors, metropolitan and peripheral, which historians have suggested that the motivation becomes more apparent.