Vaalbara

Vaalbara is a hypothetical Archean supercontinent made up of two large pieces of Earth's crust called cratons. These cratons are the Kaapvaal craton, which is located in present-day eastern South Africa, and the Pilbara Craton, found in north-western Western Australia. The name Vaalbara comes from the last four letters of each craton's name. Scientists believe that these two cratons came together to form one of Earth's earliest supercontinents.

The rocks in these cratons are very old, dating from about 3.6 to 2.7 billion years ago, which is measured in Ga, short for giga-annums or billion years. This makes Vaalbara an important piece in the puzzle of how our planet looked and changed billions of years ago. Studying Vaalbara helps scientists understand how Earth's continents moved and shaped the world we live on today.

Existence and lifespan

Scientists have debated whether Vaalbara, a very old supercontinent, actually existed. In 1976, a scientist named Alan Button noticed similarities between rocks in South Africa and Australia. He thought these areas were once connected, but placed Madagascar between them.

Another scientist, Cheney, suggested in 1996 that South Africa’s Kaapvaal craton and Australia’s Pilbara craton formed a continent he named Vaalbara. Some supporting evidence comes from magnetic studies of ancient rocks. However, not all scientists agree. Some believe the similarities are due to global processes affecting many places.

Vaalbara may have been stable for about a billion years, similar to later supercontinents like Gondwana and Rodinia. Some think an even older version of Vaalbara might have existed, but this cannot be proven.

Evidence

The Kaapvaal craton in South Africa and the Pilbara craton in Western Australia share similar rock layers from very early in Earth's history. Scientists have found evidence of ancient meteorite impacts in both places, with four large impacts occurring between 3.2 and 3.5 billion years ago. These impacts created high temperatures that turned sediments into small, glassy balls called spherules. Some of the oldest known spherules, dating back 3.5 billion years, have been found in both South Africa and Western Australia.

Studies of rock structures and magnetic data suggest that these two cratons might have been part of the same supercontinent around 3.87 billion years ago. Both areas also show signs of ancient volcanic activity and faults from that time period.

Origin of life

See also: Abiogenesis

The Pilbara and Kaapvaal cratons have some of the oldest known signs of tiny life from a very long time ago. Scientists have found clues that very simple plants and tiny living things may have existed there billions of years ago. The oldest clear proof of tiny plants making food from sunlight was found in very old rocks in the Pilbara Craton. Some scientists think these signs might be from very old types of life that are no longer around today.