Instructions: In this task, you are given a question. You have to answer the question based on your information.
Input: After the formation associated to a period of crustal thining what amount of time did a long-lasting mountain building event occur?
Output:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
50 million years