The Galapagos Rise is an underwater geological feature in the eastern Pacific Ocean. This mountain range lies approximately 1,000 kilometers south-southwest of the Galapagos Islands and 2,000 kilometers west of Peru. It consists of inactive ridge and transform segments within the northwestern Nazca Plate. Identified in 1964, the Galapagos Rise represents an extinct spreading center active during the Miocene period.
Geological Formation and Tectonic Plates
The Galapagos Rise formed due to tectonic forces in the eastern Pacific. It emerged after the ancient Farallon plate fragmented into the Cocos and Nazca plates. This reorganization disrupted spreading along the East Pacific Rise, leading to a rotation in spreading direction and the development of new spreading centers. The Galapagos Rise propagated southward as one of these new centers, contributing to the formation of the Bauer microplate between 18.5 and 18 million years ago.
Initially, spreading between the Nazca Plate and the Bauer microplate averaged around 170 millimeters per year. This expansion gradually transferred to the East Pacific Rise approximately 6.5 million years ago, eventually ceasing completely on the Galapagos Rise about 5.8 million years ago. Despite the cessation of spreading, evidence suggests that magmatism, the movement of molten rock, continued along parts of the rise for at least another 2 million years. These post-spreading lavas exhibit a more alkali-rich composition compared to those extruded when the spreading center was active.
The Galapagos Hotspot and Island Creation
The Galapagos hotspot, a stationary plume of superheated material rising from Earth’s mantle, creates the Galapagos Islands. As the Nazca Plate moves eastward over this hotspot, volcanic material erupts, building seamounts that eventually emerge above sea level. This process results in an island chain where islands furthest from the current hotspot are generally older and more eroded. For example, Española Island, one of the oldest, has lava dating back 3.0 to 3.4 million years, while Fernandina Island, one of the youngest, formed approximately 500,000 years ago.
The interaction between the hotspot and moving tectonic plates means the islands have varying ages, with the most volcanically active islands, such as Isabela and Fernandina, currently situated above the hotspot. This relationship has also left a trail of submerged features, including the Carnegie and Cocos ridges, which extend from the archipelago and provide a geological record of the hotspot’s past activity. These ridges, similar in age, represent pathways where oceanic crust moved over the Galapagos hotspot, leaving behind volcanic traces.
Discovery of Deep-Sea Hydrothermal Vents
In 1977, deep-sea hydrothermal vents were discovered along the Galapagos Rift, also known as the Galapagos Spreading Center. Scientists aboard the submersible Alvin descended to depths of 2,550 meters to observe plumes of superheated, mineral-rich water spewing from chimney-like structures on the seafloor. These vents, with water temperatures exceeding 350 degrees Celsius, do not boil due to the immense pressure at these depths. The rapid cooling of the vent fluid upon contact with cold seawater causes dissolved minerals to precipitate, forming the characteristic black or white “smoke.”
The discovery changed the understanding of where life can exist on Earth, as these deep-sea ecosystems thrive without sunlight. Instead of photosynthesis, the food chain at these vents relies on chemosynthesis, where microorganisms use chemical compounds like hydrogen sulfide from the vent fluids to produce energy. This process supports a dense and diverse community of organisms, including giant tube worms that can grow over two meters long, large clams, mussels, and specialized crabs. The initial site visited in the Galapagos was named the “Rose Garden” due to the appearance of red-crowned tube worms.