The asthenosphereis the highly viscous, mechanically weak and ductile region of the upper mantle of the Earth. ... In some regions the asthenosphere could extend as deep as 700 km (430 mi). Hope this helps...
"The asthenosphere (Ancient Greek: ἀσθενός [asthenos] meaning "without stength", and thus "weak", and σφαίρα [sphaira] meaning "sphere") is the highly viscous, mechanically weak and ductile region of the upper mantle of the Earth. ... In some regions the asthenosphere could extend as deep as 700 km (430 mi)."
