Q: Context: During the last 10,000 years, Mount Shasta has erupted an average of every 800 years, but in the past 4,500 years the volcano has erupted an average of every 600 years. The last significant eruption on Mount Shasta may have occurred about two centuries ago.

Question: when was the last time mount shasta was active? Let's give stream of consciousness first:
The relevant information to answer the above question is: The last significant eruption on Mount Shasta may have occurred about two centuries ago. Therefore, the final answer is about two centuries ago.