Obsidan flows which you can hike on are found within the calderas of Newberry Volcano and Medicine Lake Volcano in the Cascade Range of western North America , and at Inyo Craters east of the Sierra Nevada in California . Obsidian flows which may be hiked on are found within the calderas of Newberry Volcano and Medicine Lake Volcano in the Cascade Range of western North America , and at Inyo Craters east of the Sierra Nevada in California .