Identify the correct statements. A. The fastest and deepest geostrophic currents are found at the western boundaries of ocean basins. B. Western boundary currents are more concentrated and eastern boundary currents are more diffusive. C. Brazil current is the largest of the western boundary currents. D. Canary, Benguela and Humboldt currents are eastern boundary currents. Choose the correct answer from the options given below:
A, B and D only
Understanding Ocean Currents and Western Boundary Intensification
Ocean currents are continuous, directed movements of ocean water. They are driven by several forces, including wind, tides, the Earth's rotation (Coriolis effect), and differences in water density. Geostrophic currents are a type of ocean current where the Coriolis force balances the pressure gradient force.
Analyzing Statements on Ocean Currents
Let's examine each statement provided in the question about ocean currents:
- Statement A: The fastest and deepest geostrophic currents are found at the western boundaries of ocean basins.
- Statement B: Western boundary currents are more concentrated and eastern boundary currents are more diffusive.
- Statement C: Brazil current is the largest of the western boundary currents.
- Statement D: Canary, Benguela and Humboldt currents are eastern boundary currents.
Detailed Analysis of Each Statement
Statement A & B: Western Boundary Intensification
Statements A and B relate to a phenomenon called western boundary intensification. This means that ocean currents tend to be stronger, faster, and deeper along the western edges of ocean basins (eastern coasts of continents) compared to the eastern edges (western coasts of continents). This is due to the combined effects of the Earth's rotation (Coriolis effect) which varies with latitude, and the friction at the ocean boundaries. Consequently, western boundary currents are narrow and fast, while eastern boundary currents are broad and slow.
- Statement A says fastest and deepest currents are at western boundaries. This is consistent with western boundary intensification. Statement A is correct.
- Statement B says western boundary currents are concentrated (narrow) and eastern boundary currents are diffusive (broad). This is also consistent with western boundary intensification. Statement B is correct.
Statement C: Comparing Western Boundary Currents
Western boundary currents include well-known currents like the Gulf Stream in the North Atlantic, the Kuroshio in the North Pacific, the Brazil Current in the South Atlantic, the Agulhas Current in the Indian Ocean, and the East Australian Current in the South Pacific. While the Brazil Current is a western boundary current, it is generally not considered the largest. The Gulf Stream and the Kuroshio Current are typically cited as the most powerful and largest western boundary currents in terms of transport volume. Statement C is incorrect.
Statement D: Identifying Eastern Boundary Currents
Eastern boundary currents flow towards the equator along the eastern edges of ocean basins (western coasts of continents). Let's look at the currents mentioned:
- Canary Current: Flows south along the coast of northwestern Africa (eastern North Atlantic basin). It is an eastern boundary current.
- Benguela Current: Flows north along the coast of southwestern Africa (eastern South Atlantic basin). It is an eastern boundary current.
- Humboldt Current (or Peru Current): Flows north along the coast of South America (eastern South Pacific basin). It is an eastern boundary current.
All three currents listed are indeed eastern boundary currents. Statement D is correct.
Summarizing Correct Statements
Based on the analysis, the correct statements are A, B, and D.
Evaluating the Options
We need to choose the option that includes statements A, B, and D.
- Option 1: A, B and D only - This matches our findings.
- Option 2: A, B and C only - Incorrect, as C is false.
- Option 3: A, C and D only - Incorrect, as C is false.
- Option 4: C and D only - Incorrect, as A and B are also true.
Therefore, the correct option is the one listing A, B, and D only.
Revision Table: Ocean Current Properties
| Current Type | Location in Ocean Basin | Speed | Width | Depth | Example |
|---|---|---|---|---|---|
| Western Boundary | Western edge (Eastern coast) | Fastest | Narrow (Concentrated) | Deep | Gulf Stream, Kuroshio |
| Eastern Boundary | Eastern edge (Western coast) | Slowest | Broad (Diffusive) | Shallow | Canary, Benguela, Humboldt |
Additional Information: Ocean Circulation
Ocean circulation includes both surface currents, driven mainly by wind, and deep ocean currents, driven by density differences (thermohaline circulation). Geostrophic currents are part of the large-scale surface circulation patterns, often forming gyres in each ocean basin. The imbalance between the Coriolis force and the pressure gradient force drives the initial movement of water, which is then modified by other forces, leading to the observed current patterns like western boundary currents and eastern boundary currents.
Important Questions from Oceanography
Which one of the following is not a cold current?
Which of the following positions of Sun, Earth and Moon is/are suitable for Spring Tide?
1. SYZYGY Conjunction
2. SYZYGY Opposition
3. Quadrature
Select the correct answer using the code given below :
The maximum depth of Lithosphere is found in the
The periodic rise and fall of ocean water in response to gravitational forces is called
Consider the following statements regarding 'fronts':
1. The movement of a front causes a slow change in weather in the area over which it moves.
2. Cold fronts are associated with thunderstorms.
3. Warm front is the boundary between an advancing mass of warm air where it is overriding and rising above a mass of colder air.
Which of the statements given above is/are correct?
