Vaalbara

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 are not sure if Vaalbara, a very old supercontinent, really existed. In 1976, a scientist named Alan Button saw that rocks in South Africa and Australia looked alike. He thought these places might have been connected long ago, but he believed Madagascar was between them.

Another scientist, Cheney, said in 1996 that South Africa’s Kaapvaal craton and Australia’s Pilbara craton were once part of a continent he called Vaalbara. Some clues come from studying old rocks with magnets. But not all scientists agree. Some think the rock similarities happened because of natural processes that affect many areas.

Vaalbara might have stayed in one place for about a billion years, like later supercontinents such as Gondwana and Rodinia. Some people 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 have similar rock layers from early in Earth's history. Scientists found evidence of old meteorite impacts in both places. These impacts happened between 3.2 and 3.5 billion years ago. They created high temperatures that turned sediments into small, glassy balls called spherules. Some of the oldest known spherules, from 3.5 billion years ago, have been found in both South Africa and Western Australia.

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

Origin of life

See also: Abiogenesis

The Pilbara and Kaapvaal cratons show some of the oldest signs of tiny life. Scientists found clues that very simple plants and tiny living things may have lived there billions of years ago. The oldest 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 do not exist today.