Clouds hang over the south coast of Isabela creating a curtain of drizzle. This is the garúa season - Spanish for mist. When the cold ocean currents drive the prevailing southeast winds up against Cerro Azul and Sierra Negra, the garúa shrouds the slopes of the volcanoes. We are dredging on the southern submarine terraces of Sierra Negra and Cerro Azul now, smack in the garúa.

At higher elevations on the volcanoes, the garúa clouds become thicker and more persistent. The cold ocean air is colliding with the warmer air above it. But the drizzle from the garúa is not enough to create rivers, only small springs. “It’s wet enough to cultivate orange trees and grow some grass pastures for cows,” Denny says. “And it’s enough for people to collect drinking water, but not enough for irrigation.”

A trip to the northern slopes of Galápagos volcanoes - the side shielded from the wind, also called the leeward side - reveals a dry and parched landscape. On Santa Cruz, the bus ride from Puerto Ayora to the airport on the north side crosses from the windward to the leeward side of the island. “As soon as you go over the summit its like a climate switch is thrown - it’s totally dry,” Denny Geist says.

From January to May, the Panama Current warms the ocean around the Galápagos creating a season of hot and humid weather. Cloudbursts interrupt the sunshine bringing rain almost daily. “Some years you have the garúa all year long with no real rain,” Denny says. “Other times the ocean currents become warm for so long that the rain continues all year - those are El Niños.”

Long periods of warm water don’t help the marine life. Sea lions, penguins, marine iguanas and seabirds all depend on the cold Humboldt Current, which delivers cold-water plankton to the waters around the Galápagos. Plankton and algae are at the bottom of the food chain around these islands - the health of the marine communities depends on them.

These unique weather conditions and the remoteness of the Galápagos have been important in shaping the evolution of animal life on these islands. Since Darwin’s time, these “enchanted islands” and their animals have helped us interpret how life has evolved on our planet.

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