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Difficulty: Very hardPhysical Geography of the World

Regarding global oceanography, ocean floor relief, and plate tectonic processes, which of the following statements are correct?

  1. Coastal upwelling of cold, nutrient-rich deep ocean water along the western continental margins in tropical and subtropical latitudes is driven by offshore Ekman transport.Answer
  2. B
    The highest ocean surface salinity globally is recorded directly along the Equatorial zone due to intense thermal heating and high evaporation rates.
  3. Mid-oceanic ridges are characterized by shallow-focus seismic activity and active basaltic volcanism at divergent plate boundaries.Answer
  4. Oceanic trenches mark convergent plate margins where denser oceanic lithosphere subducts beneath another tectonic plate into the asthenosphere.Answer

Answer

The statements confirming that coastal upwelling is driven by offshore Ekman transport, mid-oceanic ridges feature shallow-focus earthquakes and basaltic volcanism, and oceanic trenches mark subduction zones at convergent margins are all correct. The statement claiming maximum surface salinity occurs at the Equator is incorrect.
The correct options accurately describe physical geography phenomena: offshore Ekman transport drives coastal upwelling along western continental margins; divergent margins along mid-oceanic ridges feature shallow-focus earthquakes and basaltic magmatism; and subduction along convergent margins forms deep oceanic trenches.

Step-by-Step Solution

1
Analyze coastal upwelling dynamics and wind-driven water transport.
Trade winds blowing parallel to western coasts in tropical regions induce offshore Ekman transport, moving surface water away from the coastline and drawing cold, nutrient-dense water from deep ocean layers to upwell.
Verify the atmospheric and oceanic mechanisms behind coastal upwelling.
2
Evaluate global ocean salinity distribution.
The highest salinity occurs in subtropical high-pressure zones (20°-30° N/S) where evaporation significantly exceeds precipitation under clear skies. At the Equator, cloudiness and frequent heavy convective precipitation decrease surface salinity despite high evaporation.
Identify the primary factors influencing equatorial versus subtropical ocean salinity.
3
Examine tectonic processes and earthquake depths at mid-oceanic ridges.
As plates pull apart at divergent boundaries, mantle decompression melting produces basaltic magma and shallow-focus seismic shocks along the ridge axis.
Determine the earthquake depth and volcanic characteristics of divergent boundaries.
4
Examine subduction zone mechanics at ocean trenches.
At convergent boundaries involving oceanic lithosphere, the denser plate subducts, forming deep ocean trenches parallel to the plate boundary.
Confirm the structural relationship between convergent plate boundaries and ocean trench formation.

Key Concept

Ocean Dynamics, Salinity Distribution, and Plate Tectonic Relief Features
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Topics

Physical Geography of the World

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