Straddling the equator, ISABELA is the largest island in the Galápagos at 4558 square kilometres, accounting for well over half the total land surface of the archipelago. The island comprises six volcanoes, fused together over time: from north to south, Ecuador (790m), Wolf (1707m), Darwin (1330m) and Alcedo (1130m) make up a narrow volcanic chain that tapers into the inaccessible aa lava flow of the Perry Isthmus, on the southwestern side of which Sierra Negra (1124m) and Cerro Azul (1640m) compose the squat base of the island. Several of the volcanoes are still active, the most recent eruptions being La Cumbre on Fernandina in 2009, Cerro Azul in 2008 and Sierra Negra in October 2005.
Much of Isabela’s huge landmass is impassable, riven by fissures, blocked by jagged lava flows or tangled thickets and the rocky shores mean that there are few landing places on the island. Most of the visitor sites – Urbina Bay, Elizabeth Bay, Punta Tortuga, Punta Moreno, Punta Vicente Rocafuerte and Tagus Cove – are on its far western side, putting them in range only of the longer tours and faster boats. But it’s worth the effort, because the upwelling of cold waters off the coast makes for a nutrient-rich zone, supporting such oddities as the Galápagos penguin and the flightless cormorant, also frequently spotted on nearby Fernandina. Plentiful stocks of fish also attract whales, large schools of common dolphins and gregarious bottle-nosed dolphins – an unexpected highlight of the western islands.
Puerto Villamil, on the island’s southeastern coast, is far less developed than either Puerto Ayora or Puerto Baquerizo Moreno, but makes a quiet retreat away from the tour boats. From the town, you can also visit several interesting sites, as well as take a horse ride through the verdant highlands up to the awesome crater of Sierra Negra – provided it’s not spitting ash and lava.