context: The presence of uranium in the earth's crust is the result of geological processes that have enriched the relative proportion of uranium in the earth's surface. In the Earth's crust, uranium is still enriched through numerous processes to form different deposits. Because uranium deposits are formed in many different pathways, uranium is a typical metal normally distributed in the earth's crust [1]. Today, uranium is an important energy source and its availability as a nuclear fuel is of considerable economic importance.
question: Where does uranium occur?
answers.text: earth's crust