Why are some oceans deeper than others?
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Answer: Tectonic activity varies
Tectonic activity varies ✓ — Correct! Ocean depth depends on seafloor age and tectonic processes. At mid-ocean ridges, new crust forms (shallow). As crust moves away, it cools, becomes denser, and sinks—creating deeper basins. Trenches form where plates subduct (Mariana: 11km deep). Pacific has old, deep seafloor; Atlantic is younger and shallower overall!
Evaporation lowers levels — Wrong. Evaporation doesn't significantly lower ocean levels or depth. Depth is determined by seafloor geology and plate tectonics.
Polar ice melts unevenly — Wrong. Ice melt raises sea level slightly but doesn't explain depth differences. Ocean depth depends on seafloor age and tectonic activity.