Question: what is the primary force that generates ridge push
[{'answer': 'gravitational pull', 'provenance': [{'wikipedia_id': '977923', 'title': 'Ridge push', 'start_paragraph_id': 1, 'start_character': 406, 'end_paragraph_id': 1, 'end_character': 424, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '977923', 'title': 'Ridge push', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 597, 'bleu_score': 0.89560999100807, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7183264546625938540}, 'section': 'Section::::Abstract.'}]}]