Question

which concept is described in the theory proposed by hess?
○ continents do not move.
○ cool rock pushes through the crust.
○ trenches are sites of seafloor spreading.
○ mid-ocean ridges are sites of seafloor spreading.

Explanation:

Hess's seafloor spreading theory states that new oceanic crust forms at mid-ocean ridges as magma rises, spreads outward, and pushes older crust toward trenches. The other options are incorrect: continents do move (contradicts plate tectonics/seafloor spreading), cool rock does not push through the crust (magma, molten rock, does), and trenches are where crust is subducted, not where seafloor spreading occurs.

Answer:

Mid-ocean ridges are sites of seafloor spreading.