Oceans & Currents — Set 2

Correct Answer: A. West Wind Drift

• **West Wind Drift (Antarctic Circumpolar Current)** = the only ocean current that flows uninterrupted around the entire globe, flowing west to east around Antarctica. • **Connects three oceans** — links the Atlantic, Pacific, and Indian Oceans; it is the largest ocean current on Earth by volume transport. • 💡 Wrong-option analysis: Benguela Current: flows north along Africa's west coast, not circumpolar; Brazil Current: flows south along Brazil's coast; Peru Current: flows north along South America's west coast.

Correct Answer: B. El Nino

• **El Nino** = the phenomenon where warm Pacific surface water unusually replaces the cold nutrient-rich Humboldt Current off Peru's coast, disrupting fisheries and global weather. • **Christmas connection** — El Nino typically occurs around December (name means 'The Child' in Spanish, referring to the Christ child); it disrupts global rainfall patterns. • 💡 Wrong-option analysis: Cyclone: rotating storm system, not an ocean temperature phenomenon; Monsoon: seasonal wind reversal; La Nina: opposite of El Nino, abnormal cooling of the Pacific surface.

Correct Answer: B. Oyashio Current

• **Oyashio Current (Kurile Current)** = a cold ocean current flowing south from the Bering Sea toward Japan, rich in nutrients and marine life where it meets the Kuroshio. • **Japan fisheries** — the convergence of cold Oyashio and warm Kuroshio near Japan creates extremely productive fishing grounds similar to Grand Banks. • 💡 Wrong-option analysis: Tsushima Current: warm branch of Kuroshio flowing into the Sea of Japan; Kuroshio Current: warm current flowing north along Japan's east coast; Alaska Current: warm current in the northeastern Pacific.

Correct Answer: B. Continental Slope

• **Continental Slope** = the steeply inclined portion of the ocean floor connecting the shallow continental shelf to the deeper continental rise, marking the true edge of the continent. • **Steep gradient** — the continental slope descends at 3°-6° compared to the gentle 0.1° of the shelf, often cut by submarine canyons. • 💡 Wrong-option analysis: Oceanic Trench: deepest narrow depressions in ocean floor; Mid-Ocean Ridge: underwater mountain range at divergent plate boundaries; Deep Sea Plain: flat abyssal area beyond the continental rise.

Correct Answer: A. 35 parts per thousand

• **35 parts per thousand (ppt)** = the average salinity of the world's oceans, meaning approximately 35 grams of dissolved salts per kilogram of seawater. • **Salinity variation** — Red Sea exceeds 40 ppt due to high evaporation and low inflow; Baltic Sea is as low as 7-8 ppt due to abundant freshwater rivers. • 💡 Wrong-option analysis: 25 ppt: too low, characteristic of brackish water not open ocean; 45 ppt: extremely high salinity found only in landlocked bodies like the Dead Sea; 10 ppt: very low, typical of brackish estuaries or inland seas.

Correct Answer: D. Benguela Current

• **Benguela Current** = a cold water current flowing north along the west coast of Southern Africa, contributing to the aridity of the Namib Desert. • **Namib Desert formation** — cold Benguela Current cools the air above it, preventing moisture-laden air from rising to form rain over coastal Namibia. • 💡 Wrong-option analysis: Mozambique Current: warm current flowing through Mozambique Channel on east coast; Agulhas Current: warm current flowing south along Africa's east coast; Brazil Current: warm current flowing south along Brazil's east coast.

Correct Answer: B. Atlantic Ocean

• **Puerto Rico Trench (Atlantic Ocean)** = the deepest part of the Atlantic Ocean, located at the boundary between the Caribbean Sea and the Atlantic, with a maximum depth over 8,000 m. • **8,376 m** — the maximum depth of the Puerto Rico Trench, making it the deepest point in the Atlantic and Caribbean. • 💡 Wrong-option analysis: Pacific Ocean: Mariana Trench (~11,000 m) is the Pacific's deepest; Southern Ocean: South Sandwich Trench is its deepest; Indian Ocean: Sunda/Java Trench is the Indian Ocean's deepest.

Correct Answer: A. Gulf Stream

• **Kuroshio = Gulf Stream equivalent** = both are warm, strong western boundary currents that transport tropical heat poleward, one in the Pacific and one in the Atlantic. • **'Black Stream'** — 'Kuroshio' means 'Black Stream' in Japanese, referring to its deep indigo color; it flows north along Japan's east coast like the Gulf Stream along North America. • 💡 Wrong-option analysis: Labrador Current: cold current in North Atlantic, opposite of Kuroshio; Canary Current: cold eastern boundary current in North Atlantic; Benguela Current: cold eastern boundary current in South Atlantic.

Correct Answer: B. Abyssal Plains

• **Abyssal Plains** = vast, nearly perfectly flat areas on the deep ocean floor (3000-6000 m depth), covered with fine-grained sediments like clay and silt. • **Flattest regions on Earth** — abyssal plains are considered the flattest surfaces on the planet, formed by sediment filling in irregular volcanic ocean floor. • 💡 Wrong-option analysis: Continental Shelves: shallow extensions of continental margins; Seamounts: underwater volcanic mountains that don't reach the surface; Guyots: flat-topped seamounts, once volcanic islands.

Correct Answer: D. Somali Current

• **Somali Current** = the Indian Ocean current that uniquely reverses direction seasonally, flowing northeast in summer and southwest in winter, driven by monsoon winds. • **Monsoon-driven reversal** — Somali Current is one of the few ocean currents to reverse direction; northeast in summer (SW monsoon) and southwest in winter (NE monsoon). • 💡 Wrong-option analysis: Kuroshio Current: permanent warm current flowing north along Japan, no reversal; California Current: permanent cold southward current along North America's west coast; Gulf Stream: permanent warm northward current in Atlantic.