2. Know the difference between compositional boundaries and mechanical boundaries. COMPOSITIONAL LAYERS continental crust (10-70 km) oceanic crust (5-7 km) mantle 2900 km core inner core MECHANICAL LAYERS aesthenosphere lithosphere (10-200 km) outer core 6396 km 5150 km mesosphere 660 km https://www.vision learning.com/en/library/Earth-Science/6/Earth-Structure/69 3. Know where the discontinuities are located (Moho, Gutenberg, Lehmann, and Conrad).