Why Deserts Form Along the Andes: Atacama and Sechura

Rain Shadow + Cold Current = Extreme Aridity

Two deserts flank the western Andes:

Atacama Desert (Chile/Peru)

• World's driest non‑polar desert (<25 mm/yr).
• Andes block moist Amazon/Trade winds (rain shadow).
• Cold Humboldt Current cools air, suppressing convection and rain.

Sechura Desert (Peru)

• Also in Andean rain shadow, cooled by Humboldt Current.
• Slightly wetter than Atacama due to equatorial proximity and occasional Amazon moisture.

Mechanism

Mountains force moist air up, dumping rain on eastern slopes; descending air warms and dries on western side. Cold offshore current further stabilizes air, preventing cloud formation.