Scientists in the United States say the Grand Canyon is nearly three times as old as earlier estimates. They say they found evidence that the Grand Canyon began forming seventeen million years ago. That is eleven million years earlier than other studies have shown.
Geologists at the University of New Mexico carried out the new study. Their findings were published last month in Science magazine.
Other scientists say the findings fit with earlier theories about how the Grand Canyon may have been formed. But some experts on Earth's development disagree. They say the study fails to support earlier findings.
VOICE ONE: The Grand Canyon is a popular stop for visitors to the southwestern United States. It stretches up to twenty-nine kilometers wide and nearly two kilometers deep. Yet its age has long been an issue of scientific debate.
Scientists have often used geologic events to describe the history of the Grand Canyon. Such events have included rock flows and sedimentary rock, or rock formed from other rocks. Generally, this method is only able to confirm ages of rock formations up to one million years ago.
VOICE TWO: Instead, the American geologists used a uranium-lead dating method that finds ages of minerals back tens to hundreds of millions of years. They dated minerals from caves at different depths of the canyon's walls. Minerals from openings on hillsides are less likely to suffer damage from water or other causes of erosion.
The uranium-lead dating system helped the geologists estimate water levels over time as river water cut through the rock to form the Grand Canyon. Their findings suggest that the rate of erosion was much slower in the western canyon than in the eastern part.
VOICE ONE: Today the Colorado River runs along the four hundred forty-six kilometer long canyon. Based on their findings, the geologists believe a separate river began the formation of the Grand Canyon. They say the canyon started instead from the west by a river about seventeen million years ago. Another river began forming a canyon from the east. Over time, the rivers connected to each other. The geologists estimate the two canyons joined together about six million years ago.
This SCIENCE IN THE NEWS was written by Brianna Blake, Jill Moss and Mario Ritter. Brianna Blake was also our producer.
