Geologists uncover surprising insights into Easter Island's volcanic history

Geologists exploring the enigmatic Easter Island have uncovered intriguing revelations about the planet's geological processes.

A research team from Colombia’s Universidad de Los Andes, headed by Cuban geologist Yamirka Rojas-Agramonte, visited the island to date zircon minerals—a reliable method for determining the ages of volcanic formations. They shared their findings in a preprint study on Authorea, Caliber.Az reports, citing foreign media.

In a surprising twist, the analysis of these ancient minerals revealed that the Earth's mantle operates quite differently than previously believed, specifically moving much slower than expected. Given that Easter Island is volcanic—its lava deposits resting on an oceanic plate that isn't significantly older than the volcano itself—dating the zircon minerals (some of which are thought to be around 2.5 million years old) was ideal for establishing the island's age.

As magma cools, zircon minerals crystallize, allowing uranium within them to decay into lead. By understanding this process and its duration, scientists can accurately date the minerals to determine the island's age. However, the results were startling: rather than being around 2.5 million years old, some minerals appeared to be as much as 165 million years old. 

This finding contradicts established knowledge about the movements of the Earth's mantle and volcanic activity. Despite the different ages indicated by the zircon deposits, their similar composition led researchers to hypothesize that they all originated from the same magma source. This raises an intriguing question: if true, it would imply that the underlying plate is younger than the zircon minerals themselves. The situation is complex, but it is indeed feasible. The volcanoes on Easter Island are classified as "hotspot volcanoes," which develop from rock rising from the Earth's mantle through what are known as "mantle plumes."

As these plumes approach the base of the Earth's tectonic plates, the surrounding rocks and the plume itself melt, resulting in the formation of volcanoes that remain stationary while the plates drift above them. This movement can lead to the creation of entirely new volcanoes over time. 

However, maintaining activity for 165 million years, as suggested by the recent mineral findings, is unprecedented. "The challenge is that the tectonic plates formed 165 million years ago have largely vanished into subduction zones," stated geologist Douwe van Hinsbergen from Utrecht University. 

By Naila Huseynova