<Table> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Th_colspan="2"> History </Th> </Tr> <Tr> <Th_colspan="2"> United States </Th> </Tr> <Tr> <Td> Name: </Td> <Td> Glomar Challenger </Td> </Tr> <Tr> <Td> Owner: </Td> <Td> Global Marine Inc . </Td> </Tr> <Tr> <Td> Builder: </Td> <Td> Levingston Shipbuilding Company, Orange, Texas </Td> </Tr> <Tr> <Td> Laid down: </Td> <Td> October 18, 1967 </Td> </Tr> <Tr> <Td> Launched: </Td> <Td> March 23, 1968 </Td> </Tr> <Tr> <Td> Acquired: </Td> <Td> August 11, 1968 </Td> </Tr> <Tr> <Td> In service: </Td> <Td> 1968 </Td> </Tr> <Tr> <Td> Out of service: </Td> <Td> 1983 </Td> </Tr> <Tr> <Td> Fate: </Td> <Td> Scrapped, c. 1983 </Td> </Tr> <Tr> <Th_colspan="2"> General characteristics </Th> </Tr> <Tr> <Td> Type: </Td> <Td> Deep sea drilling platform </Td> </Tr> <Tr> <Td> Length: </Td> <Td> 400 ft (120 m) </Td> </Tr> <Tr> <Td> Beam: </Td> <Td> 65 ft (20 m) </Td> </Tr> <Tr> <Td> Draft: </Td> <Td> 20 ft (6.1 m) </Td> </Tr> <Tr> <Td> Speed: </Td> <Td> 12 knots (22 km / h; 14 mph) </Td> </Tr> <Tr> <Td> Endurance: </Td> <Td> 90 days </Td> </Tr> <Tr> <Td> Sensors and processing systems: </Td> <Td> ITT Model 4007AB Satellite Navigation System </Td> </Tr> <Tr> <Td> Notes: </Td> <Td> Can drill to a depth of 22,500 ft (6,900 m), in a water depth of up to 20,000 ft (6,100 m). </Td> </Tr> </Table> <Tr> <Th_colspan="2"> History </Th> </Tr> <Tr> <Th_colspan="2"> United States </Th> </Tr>

How did drilling by the glomar challenger support seafloor spreading