This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Research led by a University of Wollongong (UOW) Ph.D. candidate may have solved one of Earth's most perplexing geological mysteries: What caused the Great Unconformity? Published in Nature, the study argues that the gentle rise and fall of whole continents over hundreds of millions of years, caused by hot currents deep below Earth's crust, led to the confounding disappearance of huge swaths of Earth's geological record.
Ph.D. candidate and lead author Santosh Dhungana said the Great Unconformity had long puzzled scientists, but theories about the geological gap had not been thoroughly tested. "Imagine a book where a huge section in the middle has been ripped out. The Great Unconformity is that gap in Earth's story, with the narrative jumping from the early chapters straight to a much later part of the story.
Our research suggests these pages weren't lost by chance," he said. Layers of rock usually stack up in chronological order, with the oldest at the bottom and the youngest at the top. But in locations throughout the world, sedimentary rocks of the Cambrian period, around 540 million years old, sit directly on top of much older crystalline rocks such as granite, which can be more than a billion years old.
The gap between the two periods is the Great Unconformity. One of the most striking examples of the Great Unconformity is found in the Grand Canyon in the United States, once part of the ancient continent known as Laurentia (modern North America). Evidence of the geological gap has also been found in Europe, Australia, Africa and Asia.
Depending on the location, the missing record stretches from 200 million years to well over a billion. By modeling patterns of mantle convection over hundreds of millions of years, Dhungana and co-author Nicolas Flament, an associate professor and Dhungana's supervisor, were able to piece together the puzzle of Earth's history and geological formation. Deep beneath the surface, Earth's mantle is made of hot rock that is solid and moves very slowly.
These currents, known as mantle convection, can gently lift huge areas of land or let them sink back down. Dhungana and Flament found that across the ancient continental cores of Laurentia, Baltica (northern Europe) and North China, currents in Earth's mantle triggered the continents to rise during the Neoproterozoic era, which spans 1 billion to about 540 million years ago. This era ended with the start of the Cambrian period, which brought an explosion of animal life on Earth.
Extract — continue reading at the source.
