how far have we drilled into the earth
The Kola Superdeep Borehole on the Kola peninsula of Russia reached 12.262 kilometres (7.619 mi) and is the deepest penetration of the Earth's solid surface. The German Continental Deep Drilling Program at 9.1 kilometres (5.7 mi) has shown the earth crust to be mostly porous. Drillings as deep as 2.1 kilometres (1.3 mi) into the seafloor were achieved at DSDP / ODP / IODP Hole 504B. Because the continental crust is about 45 km thick on average, whereas oceanic crust is 6-7 km thick, deep drillings have penetrated only the upper 25-30% of both crusts.