Answer: Glaciers caused the scarring
Explanation: Continental drift was a theory that explained how continents shift position on Earth's surface. Set forth in 1912 by Alfred Wegener, a geophysicist and meteorologist, continental drift also explained why look-alike animal and plant fossils, and similar rock formations, are found on different continents.
The theory of continental drift
Wegener thought all the continents were once joined together in an "Urkontinent" before breaking up and drifting to their current positions. But geologists soundly denounced Wegener's theory of continental drift after he published the details in a 1915 book called "The Origin of Continents and Oceans." Part of the opposition was because Wegener didn't have a good model to explain how the continents moved apart.
The Old Immigration Wave was a group of people that were actually immigrants themselves whereas The New Immigration Wave can be people who weren't immigrants but there family members were or ancestors.
Trade across the Sahara became possible and it impacted West African empires by influencing them on a cultural level. The peak of Saharan trade extended from the 8th century until the early 17th century.
A changing climate forced people to migrate from cold northern locations to more temperate regions.
The long-term economic exploitation of millions of black slaves was to have a profound effect on the New World's history. Most fundamentally, it produced deep social divides between the rich white and poor black communities, the consequences of which still haunt American societies now, many years after emancipation.
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