The Peru–Chile Trench (also called the Atacama Trench) is the longest ocean trench, marking the point at which the Nazca Plate meets the South American Plate. The Nazca Plate is primarily dense ocean crust and so is being subducted beneath the more buoyant South American continental plate. The South American crust has been deformed and thickened by the convergence, creating the Andes Mountains. Melting of the rocks around the subducting slab has led to volcanism and many of the Andes’ tallest peaks are volcanoes. Earthquakes along the trench produced nine large tsunamis during the 20th century, resulting in more than 2,000 deaths. The trade winds drive surface waters offshore throughout most years, leading to upwelling of nutrient-rich deep water off the coast of Peru. This upwelling makes the water very productive and yields large fish catches, predominantly anchovies and sardines. Under El Niño conditions, however, the wind direction reverses and the fish catch plummets.