This comes according to the American Museum of Natural History in New York City. But given the ever-changing terrain, this preference is difficult to determine – and requires an understanding of how these peaks rise and fall over time.
Today’s landscape features active, domary mountain ranges and undergoing billions of years of transformations. Jim van Orman, a geochemist at Case Western Reserve University in Ohio, said this is why it is difficult to determine the age of these peaks.
Most mountain ranges are shaped by tectonic plates, giant puzzle-like panels that slide over the Earth’s scarf. Due to the interaction of different plate tectonics over millions of years, entire mountain ranges can rise towards the sky.
There are two main types of tectonic boundaries. At convergent limits, plate tectonics collide. The effect often causes the less dense plate to slide, or descend down and to the primary mantle below the other plate. Van Orman said this sunken crust could lift the ground from above and lead to huge mountain ranges, such as the Himalayas that house Mount Everest. On the other hand, varying boundaries occur where plate tectonics separate. When the slabs move away from each other, the crust extends to be thin. Hot magma rises to fill the gaps created, forming mountains and valleys like those in Basin and Range County in the western United States and northwestern Mexico.
The range began to rise from close limits about 470 million years ago, and grew longer until it began about 270 million years ago, when continents that eventually became North America and Africa collided, according to the U.S. Geological Survey. Over the next millions of years, erosion decimated its original height. The mountains we know today are thanks to the subsequent elevation that renewed their elevations. The ups and downs of highs make it difficult and subjective to name the actual age of the range.
The Appalachians “have a complex history,” Van Orman said. The original rocks are older, but they were not a mountain range when they were planned [or eroded] for much of their history.
While tracking the schedule of a range is difficult, geologists have tools to measure the age of mountain formations depending on the type of rock. When igneous and metamorphic rocks form, they generate minerals, radioisotopes, or various forms of elements that contain different numbers of neutrons in their nucleus, which can be dated. For sedimentary rocks, the researchers use evidence trapped in rock layers, such as fossils or volcanic ash, to measure the lifespan of rocks. Erosive mountain sediments ending in nearby basins can also be appropriately traced back to their peak of origin and dated, Van Orman said.
Through these measurements, geologists can attribute a spectrum of relative ages to some of Earth’s mountainous terrain. On the older side, South Africa’s Makhungwa Mountains, which range in height from 2,000 to 5,900 feet (600 to 1,800 meters), contain rocks that are 3.6 billion years old, according to NASA’s Earth Observatory. Other ancient panels that make up the heart of the continents, called “caratons,” may be part of mountain ranges and can be found in Greenland, Canada, Australia and beyond.
Other mountain ranges date back to more recent geological history; for example, those in Basin and Range, such as the Snake Range, began to emerge about 30 million years ago. Individual volcanic mountains have emerged over the past million years — some even during the past century, such as the Parícutin volcano, which unexpectedly originated from an atom field during a volcanic eruption in 1943, according to the Smithsonian National Museum of Natural History.
Geologists are still searching for when and how different mountain ranges formed on Earth. Exploring these elusive timelines can convey insights into past global climate and biodiversity, as these massive peaks affect air circulation and genetic exchange.