Sampling the upper mantle via scientific ocean drilling remains elusive. Although the technologies required for drilling to the Moho still don’t exist, we have made significant progress over the last five decades in piecing together the complex geology of the oceanic crust. Here, we highlight key findings that reveal the architecture of oceanic crust and the thermal, physical, and chemical processes that are responsible for the growth and structure of the oceanic lithosphere. These advances result from enduring efforts to drill and collect downhole geophysical logs of oceanic crust near both slow and fast spreading ridges.

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