Galápagos Islands: A Volcanic Sanctuary of Evolution and Biodiversity

Located in the Eastern Pacific Ocean, the Galápagos Islands are a breathtaking archipelago of volcanic origin that straddles the equator. Situated approximately 485 nautical miles (898 km) west of mainland South America, these islands form a province of the Republic of Ecuador. The archipelago is world-renowned for its extraordinary concentration of endemic species—plants and animals found nowhere else on Earth—which famously inspired Charles Darwin to develop his theory of evolution by means of natural selection in the 1830s.

Location of the Galápagos Islands relative to continental Ecuador

Key Facts

North Seymour Island with Daphne Island in the distance

Total Islands: 127, with 18 major islands.
Highest Point: Volcán Wolf on Isabela Island, reaching 1,707 meters (5,600 ft).
Administration: Part of Ecuador, divided into the cantons of San Cristóbal, Santa Cruz, and Isabela.
Conservation Status: A UNESCO World Heritage Site (designated 1978) and a biosphere reserve.
Population: Approximately 33,042 residents as of 2020.

Geography and Physical Landscape

The archipelago spans a vast area of ocean, with 7,880 square kilometers (3,040 sq mi) of land distributed across 45,000 square kilometers (17,000 sq mi) of water. The islands are spread over a distance of 220 km (137 mi) from Darwin Island in the north to Española Island in the south.

A photograph of the Galápagos Islands from the International Space Station in October 2020. North is to the right. The sunglint reveals features usually difficult to spot, including the crater lake in the caldera of La Cumbre, the shield volcano that formed Fernandina Island. More details via click-through.

Isabela is the largest island, accounting for nearly three-quarters of the total land area. The landscape is defined by its volcanic nature, featuring shield volcanoes and dramatic lava flows. For example, Sulivan Bay on Santiago Island showcases pahoehoe lava—a smooth, billowy type of volcanic rock—that flowed roughly a century ago.

Orthographic projection centered over the Galápagos

Satellite photo of the Galápagos islands overlaid with the names of the islands

The Major Islands and Their Unique Features

Each island in the Galápagos offers a distinct ecological and historical profile:

Isabela and San Cristóbal

Isabela is the largest island and home to the archipelago's highest peak, Volcán Wolf. San Cristóbal serves as the location for the capital city, Puerto Baquerizo Moreno.

The Wall of Tears at Puerto Villamil on Isabela, the largest of the Galapagos

Santa Cruz and Baltra

Santa Cruz is one of the most populated islands and hosts Puerto Ayora, the largest town in the archipelago. Nearby Baltra Island is a key entry point for visitors via the Seymour Airport.

From an aircraft flying out of Baltra Island (on the right) and the Santa Cruz (on the left), the Itabaca Channel is the waterway between the islands.

Puerto Ayora, the largest town in the Galápagos

Specialized Habitats

Darwin Island: Known for its diverse marine life and the "Pillars of Evolution," the remaining stumps of Darwin's Arch which collapsed in May 2021.
Floreana Island: Rich in human history, featuring Post Office Bay where 19th-century whalers left a wooden barrel for mail.
Pinta Island: Formerly the home of Lonesome George, the last of the Pinta tortoise subspecies, who died in 2012.
Wolf Island: The exclusive home of the vampire finch, which feeds partly on the blood of other birds.

The Post Barrel on Floreana Island, formerly used by sailors to pass messages to any passing ships

Pinnacle Rock on Bartolomé Island, with Santiago in the background and a ferry on the right for scale

Climate and Oceanography

Detail of the Galápagos on Abraham Ortelius's 1570 map of the Americas

The climate of the Galápagos is heavily influenced by its equatorial position and oceanic currents. Some islands experience a rain shadow effect, where higher elevations block moisture from reaching lower-lying areas. For instance, the highlands of Santa Cruz receive significantly more precipitation than the nearby Baltra Island.

The ecosystem is profoundly affected by the El Niño and La Niña cycles. During El Niño, currents that normally fertilize the waters reverse, leading to barren oceans. Conversely, La Niña strengthens these currents, triggering an explosion of phytoplankton and ocean life.

Satellite maps of the concentration of chlorophyll (representing abundance of phytoplankton) during El Niño (top) and La Niña (bottom). The color scale goes from blue at the lowest concentrations to red at the highest. Currents that normally fertilize phytoplankton reverse during El Niño, resulting in barren oceans. The same currents are strengthened by La Niña, resulting in an explosion of ocean life.

A satellite map of chlorophyll and phytoplankton concentration (top) paired with a map of oceanic surface temperatures at the same time (bottom). The thriving populations represented by green and yellow in the upper map correlate to areas of higher surface temperatures represented by yellow in the lower map (2 March 2009).

Biodiversity and Ecology

The chart of the Galápagos published by the English pirate William Ambrosia Cowley in 1684, the source of many of the islands' English names

The islands are a living laboratory of evolution. The Galápagos National Park and Marine Reserve protect a vast array of species, many of which are found nowhere else.

Notable Endemic and Resident Species of the Galápagos
Species	Key Characteristic	Location/Note
Marine Iguana	Only iguana that feeds in the sea	Widespread
Galápagos Tortoise	Largest living tortoise species	Santa Cruz, Isabela, etc.
Blue-footed Booby	Distinctive blue feet used in courtship	Widespread
Galápagos Penguin	Only living tropical penguin	Bartolomé Island
Waved Albatross	Only living tropical albatross	Española Island
Flightless Cormorant	Unable to fly; adapted for diving	Endemic

A Galápagos tortoise (Chelonoidis nigra) on Santa Cruz. C. nigra is the largest living species of tortoise, hunted to near extinction during the islands' whaling era.

School of scalloped hammerheads off Wolf Island

Conservation and Environmental Threats

A manuscript map of the islands from the charts drafted by James Colnett of the British Royal Navy in 1793, adding additional names

Maintaining the delicate balance of the Galápagos is a constant challenge. In 1986, a massive marine reserve was established, and the islands were designated a whale sanctuary in 1990. However, the archipelago has faced significant threats from invasive species, such as goats, rats, and pigs, which damage native flora and fauna.

Between 1996 and 2006, a US$5 million eradication plan successfully removed most introduced goats, deer, and donkeys. While rats have been eliminated from Rábida and Pinzón islands, they remain a threat elsewhere. Other pressures include unbridled tourism and overfishing. Due to these threats, UNESCO placed the islands on the List of World Heritage in Danger from 2007 to 2010, removing them only after Ecuador demonstrated significant progress in conservation efforts.

Frequently Asked Questions

Gen. José de Villamil, founder of the Ecuadorian Navy and first governor of the islands

The 1841 Admiralty chart drafted from FitzRoy's survey of the islands on HMS Beagle

Gould's illustration of Darwin's finches

Eleanor Roosevelt visiting U.S. servicemen at Beta Base (Seymour Airport) on Baltra during World War II[58]

Ecuadorian children on a Galápagos beach in the 1920s

Brown pelican (Pelecanus occidentalis), Tortuga Bay

Bottlenose dolphins jumping offshore of the islands

Adult Galápagos sea lion resting on a park bench in Puerto Baquerizo Moreno

Who is the most famous scientist associated with the Galápagos?

Charles Darwin visited the islands in the 1830s. His observations of the endemic species, particularly the variations in mockingbirds and finches between islands, inspired his theory of evolution by natural selection.

What is the largest island in the archipelago?

Isabela is the largest island, comprising nearly three-quarters of the total land area of the Galápagos.

What happened to Lonesome George?

Lonesome George was the last remaining Pinta tortoise. He was moved to the Charles Darwin Research Station on Santa Cruz Island for breeding attempts, but he died in June 2012 without producing offspring.

How do El Niño and La Niña affect the islands?

El Niño causes currents to reverse, reducing the nutrients available for phytoplankton and leading to barren oceans. La Niña strengthens these currents, resulting in an abundance of phytoplankton and a surge in marine life.

Are the Galápagos Islands protected?

Yes, the islands are protected as part of Ecuador's Galápagos National Park and Marine Reserve. They are also recognized as a UNESCO World Heritage Site and a biosphere reserve.