How to determine the geological age of a mountain?

Most of the mountains we see may seem ancient - but little is known about the geology while some are just 'toddlers', others are 'elderly'. ".

According to the American Museum of Natural History in New York City, generally high mountain ranges like the Himalayas tend to be younger, while ranges with shorter peaks after millennia of erosion like the Appalachians are generally older. .

Because of Earth's ever-changing topography, this superpeak is difficult to delineate — and it requires an understanding of how these peaks rise and fall over time.

Sunrise over Great Smoky Mountains National Park in Gatlinburg, Tennessee, which is part of the Appalachian Mountains.

Today's landscape is characterized by active and inactive mountain ranges that have undergone many changes over billions of years. That's why it's so difficult to pinpoint the exact ages for these peaks, says Jim Van Orman, a geochemist at Case Western Reserve University in Ohio.

Most mountain ranges are formed by tectonic plates, giant puzzle-like rocks that glide across the Earth's mantle. As different tectonic plates interact over millions of years, entire mountain ranges can rise up into the sky.

There are two main types of tectonic boundaries. At convergent boundaries, tectonic plates collide with each other. The collision usually causes the lower density plate to sink or go underneath and into the mantle below the other plate. That subducted crust can lift the land upwards and form huge mountain ranges, like the Himalayas, where Mount Everest is located, Van Orman said. On the other hand, divergent boundaries occur when tectonic plates separate from each other. As the plates pull apart, the crust stretches to become as thin as taffy. Hot magma rises to fill the voids created, creating mountains and valleys like those in the Basin and Mountains province of the western United States and northwestern Mexico.

There are many nuances when it comes to the duration of mountain ranges. Take for example the Appalachian Mountains.

The extent began to increase from a converging boundary about 470 million years ago and even higher starting about 270 million years ago, when the continents that eventually became North America and Africa collided. , according to the United States Geological Survey. Over the course of millions of years, erosion reduced its original elevation. The mountains we know today are thanks to a later upgrade that rejuvenated their altitude. This rise and fall in elevation - a characteristic feature of mountains - makes it difficult and subjective to label the actual age of a range.

Van Orman told Live Science. "There's the age of the original rocks, but it wasn't a mountain range when it was worn [or eroded] for a large part of its history. So, how old is it really?"

Although tracing the timeline of a mountain range is complicated, geologists have the tools to measure the age of mountain components depending on the type of rock. As igneous and metamorphic rocks form, they produce minerals and radioisotopes, or variations of elements with different numbers of neutrons in their nuclei, that can be dated. For sedimentary rocks, researchers use clues trapped in rock layers, such as fossils or volcanic ash, to gauge the age of the rock. Erosted mountain sediments ending up in nearby basins can also be traced back to their peak origins and appropriately dated, Van Orman said.

From these measurements, geologists can determine a relative age spectrum for some of the Earth's mountainous landforms. In terms of age, the Makhonjwa Mountains in southern Africa, which are only 2,000 to 5,900 feet (600 to 1,800 meters) high, contain rocks that are 3.6 billion years old, according to NASA's Earth Observatory. NASA's Earth Observatory. Other ancient rocks that make up the continent's core, known as "craters," may have once been part of mountain ranges and can be found in Greenland, Canada, Australia and beyond.

Other mountain ranges date back to more recent geologic history; For example, species in the Basin Province and Range, such as the Snake Range, began to appear about 30 million years ago. Individual volcanoes have risen over the past million years - some even over the past century, like the Parícutin volcano, which suddenly arose from a cornfield during an eruption in 1943, according to the Bao. Smithsonian National Museum of Natural History.

Geologists are still studying when and how different mountain ranges on Earth formed. Exploring these elusive timelines could yield insights into past global climate and biodiversity, as these massive peaks affect air circulation and exchange. genes.

'It helps to reconstruct the entire history of the Earth,' says Van Orman. Going back in time, the only real evidence we have for [plate motion] is to look at these old mountain belts."