The oceanic crust covers almost 57% of the Earth's surface and is created by seafloor spreading at mid-ocean ridges. Although crustal structure is similar everywhere, seismic experiments near spreading ridges indicate that seismic velocities in the top of the igneous crust are typically much lower than those in mature oceanic crust. While profound differences between juvenile and mature crust have long been recognized, little is known about the relationship between crustal aging and the properties of oceanic crust.
German researchers from the Universities of Hamburg and Bremen explored seafloor created over the last 8 million years at the “super-fast” spreading East Pacific Rise south of the Garrett Fracture Zone (14–16°S) during a 52-day marine geophysical survey aboard the R/V Sonne. The seafloor in that area spreads at a rate of 150 mm/yr. The researchers studied age-dependent trends in the structure and properties of upper oceanic crust; this was the first study in nearly two decades to use an integrated approach to study variations and heat transfer in the upper crustal structure.