How were these iconic landforms created?

The Himalayan mountain range in Nepal
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They're massive, they're all-natural and, in most cases, they're millions of years older than we are. So how were these amazing landforms created?

Question 1 of 12

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Lake Superior
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The Great Lakes were formed by:

The Great Lakes were formed about 20,000 years ago as the Earth's climate warmed and glaciers melted and retreated. According to the National Oceanic and Atmospheric Administration (NOAA), the glacier that made the Great Lakes was at least 2 miles thick and gouged the ground as it moved, creating the lake basins and filling them with melted glacial water.

Question 2 of 12

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Kilauea volcano on the Big Island of Hawaii
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The Hawaiian islands were formed by volcanoes. How many volcanoes make up the Big Island?

The Big Island is constructed of five major volcanoes: Kilauea, Mauna Loa, Mauna Kea, Hualalai and Kohala. Each of the eight main islands is made up of at least one primary volcano, according to the University of Hawaii. Mauna Loa is the largest active volcano on Earth, and Kilauea is one of the most productive, meaning it erupts the most lava.

Question 3 of 12

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South Rim of the Grand Canyon in Arizona
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The Grand Canyon was formed by:

The snow-fed Colorado River started carving the Grand Canyon 5 or 6 million years ago, according to the National Park Service. Cutting from the river made the canyon deep, but the region's dry climate prevents the canyon from widening, which is why we have a canyon instead of a river valley.

Question 4 of 12

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The Himalayan mountain range in Nepal
Photo: Olga Danylenko/Shutterstock
When did the Himalayan mountain range start forming?

The Himalayas were formed when the Indian plate and the Eurasian plate collided 50 million years ago. The plates continue to collide to this day, resulting in the mountain range rising by more than 1 centimeter each year, the Geological Society of London says.

Question 5 of 12

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The Cave of the Crystals in Mexico
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The Cave of the Crystals in Mexico contains a forest of enormous pillars that are half a million years old. What are the crystals made of?

According to the BBC, the "enormous crystals are believed to have formed when gypsum-saturated groundwater flowed through the caves, and was heated and cooled by hot magma below." This cave, located nearly 1,000 feet underground in the Mexican state of Chihuahua, lies above an intrusion of magma, so it gets very hot.

Question 6 of 12

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Sahara Desert in Africa
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Africa's Sahara Desert, the largest hot desert in the world, was created when?

Until recently, the Sahara Desert was thought to be only 2 or 3 million years old. However, sand dune deposits in Chad were discovered that showed the desert actually dates back 7 million years. It was formed when a giant ocean called Tethys, which was the origin of the Mediterranean, Black and Caspian seas, began to shrink, weakening the monsoon season and drying out Northern Africa.

Question 7 of 12

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Great Blue Hole in Belize
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The Great Blue Hole is part of the Belize Barrier Reef. How did the hole get there?

The Great Blue Hole is a large underwater sinkhole (984 feet across and 410 feet deep) and a mecca for scuba divers, where the crystal clear water allows for plenty of marine life viewing. It started forming as a limestone cave during the last glacial period when sea levels were much lower. As the ocean rose, the caves flooded and collapsed, creating a "vertical cave," Atlas Obscura reports.

Question 8 of 12

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A man floats in the Dead Sea
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The Dead Sea is a salt lake that sits 1,400 feet below sea level. At some depths, it's 10 times saltier than the ocean! Why is it so salty?

The Dead Sea sits in the deepest continental basin on Earth. Because of this, it can accept water coming from uphill sources (like Sea of Galilee) but there's nowhere for the water to drain. So the only way water can escape is through evaporation, and when it evaporates, it leaves behind its salts.

Question 9 of 12

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The Giant's Causeway in Northern Ireland
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Giant's Causeway in Northern Ireland consists of 40,000 stone pillars jutting out from the coastline. How long have they been there?

"The Giant’s Causeway resulted from successive flows of lava inching toward the coast and cooling when they contacted the sea. Layers of basalt formed columns, and the pressure between these columns sculpted them into polygonal shapes," according to the Encyclopedia Britannica. They're about 15 to 20 inches in diameter and up to 82 feet tall.

Question 10 of 12

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Salar de Uyuni in Bolivia
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Salar de Uyuni in Bolivia is the largest salt flat in the world. How do salt flats form?

Salt flats are dried-up lakes that form in basins where rainfall can't drain away. In desert climates, the water evaporates faster than it can be replenished, leaving salt and minerals behind in a solid layer.

Question 11 of 12

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China's Stone Forest
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Columns of limestone form what looks like a forest of stones in China's Yunnan Province. How did the stones get their unique shape?

About 270 million years ago, the Stone Forest was a shallow sea. Huge deposits of sandstone and limestone accumulated in the basin, and over time, these deposits rose. Wind and running water shaped them into the formations we know today, which cover about 115 square miles.

Question 12 of 12

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The Himalayan mountain range in Nepal
Photo: Olga Danylenko/Shutterstock
How long did it take Australia's Uluru or Ayers Rock to become the inselberg it is today?

Uluru originally sat at the bottom of a sea, but today it rises about 1,140 feet above ground. Interestingly, the bulk of its mass is underground — it extends down about 1.5 miles.

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The Himalayan mountain range in Nepal
Photo: Olga Danylenko/Shutterstock