Which climatic phenomenon is irregular, occurring every few years, affecting the equatorial Pacific and producing unusually warm, nutrient-poor water off northern Peru and Ecuador?

• A. El Nino
• B. Erosion
• C. Steppes
• D. Taiga

Answer: (A)

El Niño is a climatic pattern that involves warming of surface waters in the central and eastern equatorial Pacific. It tends to appear irregularly, roughly every few years. When it occurs, the trade winds weaken, allowing warm water to move east toward the coast of South America. That warm surface water suppresses upwelling of the colder, nutrient-rich water off northern Peru and Ecuador, leading to unusually warm, nutrient-poor waters and disruptions in marine life and fisheries there. The description in the question matches this warming pattern and its effects. The other options refer to processes or biomes (erosion, steppes, taiga) and don’t describe a Pacific warming event.