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 hard 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. Long ago, Antarctica was part of a huge landmass called Gondwana. This land broke apart, and Antarctica became the continent we know today.

History of study

See also: History of Antarctica and List of Antarctic expeditions

Antarctica was the last place humans visited. The first people to land below the Antarctic Circle were in 1820. They were led by Admiral Fabian Gottlieb von Bellingshausen and his crew during the Russian Antarctic Expedition.

Early explorers mostly wanted to know if Antarctica was useful, so they did not focus much on science. In 1829, an American scientist named James Eights found the first fossil in Antarctica on King George Island, but he left it there.

Later, from 1839 to 1842, the Ross expedition led by Captain James Clark Ross found several islands in Antarctica. These islands, like Seymour Island and Cockburn Island, are now known to have many fossils, but they did not collect any 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 studied by scientists in 1894.

Scientific study of Antarctica grew after the Antarctic Treaty System began in 1961. This treaty set Antarctica aside just for science. Since then, learning about Antarctica's past has become very important, even though it is hard because of the harsh weather, deep cracks in the ice, and dangerous snow slides.

Archean

The oldest rocks in the East Antarctic Shield are 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 have old rocks called granulites from this period.

Proterozoic

The Mawson craton of East Antarctica and Australia shows very old movements of Earth's plates from the middle of a long period called the Mesoproterozoic. We can see this in places like Terre Adelie, King George V Land, and the Miller Range in the central Transantarctic Mountains.

In the Late Proterozoic, rocks called the Rayner Complex can be found in Enderby Land and western Kemp Land. The Rauer Islands, made of special metamorphic rocks, are also from this time, about 1,106 million years old. There are 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 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. The basaltic lavas of the Straumsnutane Formation, about 821 million years old, are the top layer of this supergroup. To the east, there is an 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. 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 created large masses of rock called batholiths and layers of fragmented rocks called pyroclastics.

Paleozoic

See also: Terra Australis Orogen

Long ago, during the Cambrian time, a special kind of rock called a carbonate platform formed along the edge of a big landmass named Gondwana. This created the Shackleton Limestone on top of older rocks. Big events called the Ross orogeny happened, changing the rocks in the Transantarctic Mountains.

Later, in the Late Paleozoic time, Antarctica moved over the South Pole and became very cold. During this icy time, up to 375 meters of rocks formed from glaciers.

In the Cambrian period, the climate was mild. Lots of sandstones, limestones, and shales formed. The seas had many sea creatures. As time passed, the climate cooled, and glaciers began to form. By the Permian period, plants like ferns grew in swamps, which later turned into coal.

Mesozoic

See also: Polar forests of the Cretaceous and South Polar region of the Cretaceous

During a time called the Triassic, a huge landmass named Pangea began to split 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, there was a lot of volcanic activity in the mountains and peninsulas of Antarctica. By the Late Jurassic, the Antarctic Peninsula became a narrow chain of volcanic islands. This volcanic activity continued into a time called the Early Cretaceous. Around this time, Antarctica separated from Australia and later from New Zealand.

Cenozoic

Antarctica moved away from South America at the Drake Passage during the Miocene. This made Antarctica alone and colder. By the Middle-Late Eocene^{: 43, 54–57, 226}, big ice sheets formed there.