Geology of Antarctica

The geology of Antarctica covers the geological development of the continent through the Archean, Proterozoic and Phanerozoic eons. Studying Antarctica's geology is challenging because most of the land is hidden under a thick layer of ice. Scientists use special tools like remote sensing to learn about what lies beneath.

West Antarctica looks a lot like the Andes in South America. The Antarctic Peninsula formed when old sea sediments were pushed up and changed by heat and pressure during the late Paleozoic and early Mesozoic eras. This area also has volcanic rocks such as andesite and rhyolite from the Jurassic Period. There are still signs of volcanoes in places like Marie Byrd Land and Alexander Island.

East Antarctica is made of very old rocks, some more than 3 billion years old. It has layers of different rocks on top, like sandstones, limestones, and shales, formed in older times. More than 170 million years ago, Antarctica was part of a huge landmass called Gondwana. This land broke apart, and Antarctica became the continent we know today around 35 million years ago.

History of study

Antarctica was the last continent where humans set foot. The first landings below the Antarctic Circle happened in 1820 by Admiral Fabian Gottlieb von Bellingshausen and his crew during the Russian Antarctic Expedition.

Early explorers were mostly interested in whether Antarctica had any economic value, so scientific research was not a big focus. In 1829, an American naturalist named James Eights found the first fossil in Antarctica on King George Island, but he left it where he found it.

Later, from 1839 to 1842, the Ross expedition led by Captain James Clark Ross discovered several islands in Antarctica that are now known to have many fossils, such as Seymour Island and Cockburn Island, though they did not record any fossils at the time.

In 1892 to 1893, Captain Carl Anton Larsen and his crew landed on Seymour Island and collected fossil shells. These fossils were sent to the University of Oslo and were the first Antarctic fossils to be formally described by scientists in 1894.

Scientific study of Antarctica grew after the Antarctic Treaty System began in 1961, which set Antarctica aside just for science. Since then, learning about Antarctica's past has become very important, although it remains challenging due to harsh weather, deep cracks in the ice, and dangerous snow slides.

Archean

The oldest rocks in the East Antarctic Shield are found in the Napier Mountains. These rocks are part of the Napier orogeny and formed very early in Earth's history, about 4000 Ma, during the Archean time. The Vestfold Hills also have very old rocks called granulites from this period.

Proterozoic

The Mawson craton of East Antarctica and Australia shows evidence of movement of Earth's plates from very old times through the middle of a very long period called the Mesoproterozoic. This evidence can be found in places like Terre Adelie, King George V Land, and the Miller Range in the central Transantarctic Mountains.

In the Late Proterozoic, a group of rocks called the Rayner Complex can be seen in Enderby Land and western Kemp Land. The Rauer Islands, made of special types of metamorphic rocks, are also from this time, about 1,106 million years old. There are many thin pieces of rock called dykes in areas like the Vestfold Hills and Napier Complex, placed there between about 1,200 to 1,400 million years ago. Large bodies of a type of rock called charnockite are found in East Antarctica, showing that a big mass of molten rock pushed up into older rocks about 1,000 million years ago. In the Borg Massif area of western Dronning Maud Land, very old granites are covered by younger rock layers called the Ritscherflya Supergroup. This group includes sedimentary and volcanic rocks, with some parts pushed in by later rock layers. The basaltic lavas of the Straumsnutane Formation, about 821 million years old, are the top layer of this supergroup. To the east, there is another area of changed rocks called the H.U. Sverdrupfjella terrane. The Sør Rondane Mountains have rocks changed by heat and pressure from the Late Proterozoic, with later rocks pushing into them. Eastern Queen Maud Land has complexes of gneisses and other rocks from the Late Proterozoic.

During the Precambrian, layers of rock formed in deep ocean areas along the side of an old landmass called Gondwana, where the Transantarctic Mountains are today. These layers were mostly deep-sea deposits. Important layers include the Turnpike Bluff Formation, the Beardmore Group, and the Skelton Group. The Beardmore orogeny happened in the Late Proterozoic, changing the rocks in the central Transantarctic Mountains. Limestones from the Cambrian period lie on top of these changed rocks. Volcanic activity at this time created large masses of rock called batholiths and layers of fragmented rocks called pyroclastics.

Paleozoic

Mesozoic

During a time called the Triassic, a huge landmass named Pangea started to break apart. Antarctica moved north away from the South Pole as part of a landmass called Gondwana. Layers of rock formed along mountains and peninsulas during this time.

Later, in a period called the Middle Jurassic, lots of volcanic activity happened in the mountains and peninsulas of Antarctica. By the Late Jurassic, the Antarctic Peninsula became a narrow chain of volcanic islands. This volcanic activity kept going into a time called the Early Cretaceous. Around this time, Antarctica separated from Australia and later from New Zealand.

Cenozoic

Antarctica separated from South America at the Drake Passage during the Miocene. This separation made Antarctica geographically isolated, leading to colder climates. By the Middle-Late Eocene^{: 43, 54–57, 226}, large ice sheets had formed on the continent.