Figure F1. Scientific drilling of the oceanic lithosphere, 1968–2003. World map of the oceans showing the distribution of drill holes into in situ ocean basement formed at mid-ocean ridges. Despite more than 30 yr of ocean drilling, there are still relatively few drill holes in oceanic crust and a very poor sampling distribution in terms of basement depth, crustal age, and spreading rate. Note the clustering of drill sites along the Mid-Atlantic Ridge and in the eastern Pacific Ocean. Stars = holes drilled by DSDP and ODP.