Study details the history of Galápagos’ rich landscape
UI College of Science professor part of research to date beginnings of diverse islands
It was about 1.6 million years ago that one of the most diverse ecosystems in the world really took shape.
Researchers now believe that time period provided the growth spurt that allowed what is now known as the Galápagos Islands near the Earth’s equator to bloom with the wide variety of plant and animal life found there today.
University of Idaho College of Science geology professor Eric Mittelstaedt is part of a research team that arrived at this conclusion in a paper published this month in the journal Earth and Planetary Science Letters. His co-authors include University of Colorado assistant professor Kristopher Karnauskas and University of Maryland professor Raghu Murtugudde.
Mittelstaedt and his colleagues used computer simulations to understand how the interactions of newly emerging islands and ocean currents led to the world-renown Galápagos ecosystem of today. Mittelstaedt used publicly available data to create a simulation of past islands, then passed his model results to Karnauskas, who placed them in a model of ocean currents and sea surface temperature to examine how the emerging islands altered the ocean currents.
Their models showed a very intense upwelling of cold water from what is called the equatorial undercurrent was created by a collision with the westernmost islands in the chain as they appeared from the water. That subsurface current was blocked by the islands, which Mittelstaedt and his study co-authors believe helped bring nutrient-rich seawater to the surface.
The collision, which began about 1.6 million years ago and continues to this day, dramatically altered the islands’ ecosystem. Mittelstaedt said that water had to go somewhere, so much of it flowed upward and brought nutrient-rich, deep ocean waters to the surface of what is now a 21-island chain.
Prior to the islands’ emergence from the Pacific Ocean, the ocean surface waters were warmer to the west of the current Galápagos Archipelago and colder to the east, near the South American continent. Blockage of the equatorial undercurrent flipped this relationship on its head, changing the temperature of surface waters and providing the key indicator that led Mittelstaedt and colleagues to recognize the emergence of new Galápagos islands.
“That tells us that the configuration of the Galápagos Islands was different” prior to 1.6 million years ago, he said.
The islands’ emergence helped create one of the world’s most unique ecosystems, which today includes four different species of tortoises as well as penguins and fur seals.
The research team’s efforts built upon the work of earlier researchers, who collected core samples to the west and east of the Galápagos and examined them for small shell-creating animals that lived millions of years ago. By examining the chemical composition of the shells, those researchers were able to determine the seawater temperatures throughout the islands’ history.
“These records allowed us to see the change in surface water temperature to the west and east of the archipelago,” Mittelstaedt said.
Such records are similar to imagery today that uses satellite measurements of sea surface temperature – which shows a large cold zone just to the west of the islands and a warmer zone to the east.
The group’s efforts have been in the works since 2009, when Mittelstaedt was working as a postdoctoral fellow at the Woods Hole Oceanographic Institution on Cape Cod in Massachusetts and Karnauskas was a faculty member there. The research continued organically as the pair worked on other projects.
In addition to helping figure out how the islands were created with such a lush mixture of biological detail, Mittelstaedt said their research also has the benefit of helping answer questions about the region’s contribution to the global climate and the difficult question of how islands form.
“It’s really hard to nail down when these islands first emerge,” he said. “This study provides a new tool for looking at geologic events.”
Their efforts should also help with research on mantle plumes, columns of hot rocks that rise through the Earth’s mantle. Mittelstaedt said he is primarily interested in seeing how the Galápagos formation relates to the volcanic processes at other mantle plume islands like Hawaii, Iceland and others.
Article by Brad Gary, University Communications and Marketing