Antarctica, defined by its massive, continental ice sheet, hides a deep and complex topography beneath the frozen surface. Researchers have worked to map the underlying landscape, revealing mountain chains rivaling the scale of those found on other continents. These hidden mountains are a fundamental part of the continent’s structure, influencing its ice, climate, and geological history. They represent a massive, physical break across the entire landmass, separating two vastly different geological provinces.
The Transantarctic Mountains: Defining the Range
The mountain range that crosses the continent is known as the Transantarctic Mountains (TAM), and it ranks among the longest mountain systems on the planet. This immense chain stretches for approximately 3,500 kilometers, beginning near the Weddell Sea and extending across the continent to the Ross Sea and Victoria Land. It is the geographic feature that physically divides Antarctica into two distinct regions: the larger, older East Antarctica and the smaller, geologically younger West Antarctica.
The TAM is not a single, continuous ridge but a collection of numerous sub-ranges, massifs, and peaks, including the Queen Maud and Pensacola Mountains. The width of the range varies significantly along its length, typically measuring between 100 and 300 kilometers across. The highest point, Mount Kirkpatrick, reaches an elevation of 4,528 meters above sea level. This sheer scale makes the mountain range a dominant force in the continent’s physical geography.
The two sides separated by the TAM are fundamentally different geologically. East Antarctica is composed of an ancient, stable continental shield (craton), while West Antarctica is an archipelago of smaller, younger crustal blocks. The TAM thus marks the boundary between a stable, ancient landmass and a region of the crust that has been extensively stretched and rifted. This makes the range a crucial marker for understanding the tectonic history of the entire continent.
Geological Formation and Age
The formation of the Transantarctic Mountains is a story of rifting and uplift, a process distinct from the crustal collision that created ranges like the Himalayas. The mountains began to take their current form about 65 million years ago, coinciding with the opening of the West Antarctic Rift System. This extension caused the crust on the western side to thin and drop, while the edge of the rigid East Antarctic block was uplifted to form the massive mountain front. The process is described as a flank uplift associated with the formation of a rift valley.
The rocks exposed in the TAM tell a story that goes back much further than the uplift event itself. The foundation of the range consists of ancient basement rocks, including granites and gneisses, formed hundreds of millions of years ago. Overlying this are thick layers of sedimentary rock, known as the Beacon Supergroup. These layers contain a remarkable fossil record, including evidence of ancient forests and coal beds, showing that Antarctica was once a temperate and vegetated part of the Gondwana supercontinent.
The final phase of uplift occurred long after the initial breakup of Gondwana, which began around 180 million years ago. During the Jurassic period, the region experienced an intrusion of dark, igneous rock called the Ferrar Dolerite, which cut through the sedimentary layers. This volcanic activity marked the beginning of the continental rifting. The mountains are a composite feature, built on ancient foundations but uplifted by recent tectonic forces related to the development of the rift valley.
Impact on Antarctic Ice Sheets and Research
The Transantarctic Mountains profoundly influence the flow and stability of the continent’s ice sheets. The range acts as a physical barrier, effectively damming the East Antarctic Ice Sheet (EAIS) and preventing its unrestricted flow toward the sea. The EAIS, which holds the majority of the world’s fresh water, is relatively stable partly because the TAM acts as a pinning point along its western margin. Ice from the EAIS must flow through large, deep valleys, known as outlet glaciers, to reach the Ross Ice Shelf.
This barrier function is also important for the stability of the West Antarctic Ice Sheet (WAIS), which is more vulnerable to melting. The TAM helps maintain the separation between the EAIS and the WAIS, slowing the rate at which eastern ice could feed into the less stable western system. Researchers study the outlet glaciers, such as the Beardmore and Nimrod Glaciers, to understand the dynamics of ice flow and how the mountains influence the rate of ice discharge.
The exposed rock faces and peaks that rise above the ice, known as nunataks, are invaluable to scientific research. These ice-free areas provide accessible sites for collecting rock samples and fossils, acting as windows into the geology beneath the ice sheet. By studying the glacial-depositional record on the slopes of the TAM, scientists reconstruct the past behavior and thickness of the EAIS over millions of years. This allows for a better understanding of how the ice sheet responded to warmer climates in the past.