{'plate tectonics': [0, 0, 0, 2], 'continental drift theory': [1, 0, 0, 0], 'alfred wegener': [1, 0, 0, 1], 'isostasy': [0, 0, 0, 1], 'theory': [14, 0, 6, 19], 'archdeacon pratt': [0, 0, 0, 1], 'erosion': [3, 0, 0, 3], 'geographical cycle': [0, 0, 0, 1], 'walter penck': [0, 0, 0, 1], 'william moris davis': [0, 0, 0, 1]}