Question: when was the last time yellowstone caldera erupted
[{'answer': 'approximately 630,000 years ago', 'provenance': [{'wikipedia_id': '379647', 'title': 'Yellowstone Caldera', 'start_paragraph_id': 2, 'start_character': 357, 'end_paragraph_id': 2, 'end_character': 388, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '379647', 'title': 'Yellowstone Caldera', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 451, 'bleu_score': 0.972782728923768, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9338594950311131164}, 'section': 'Section::::Abstract.'}]}]