What was needed in order to produce the Heezen and Tharp maps? - Collaboration between people with different skills - The opportunity for people to develop their skills and expertise in specific areas of study - The existence of sonar - The existence of a clock that could distinguish time in units shorter than a second - Research ships - Sufficient resources within a society to expend on scientific exploration - Ways to determine latitude and longitude at sea - GPS and personal computer - Deep sea cables to measure depth to the seafloor.