5 Secrets of the Grand Canyon

For many people, summer means it’s time for a road trip! One popular destination is Grand Canyon National Park in Arizona. Every year, about 6 million visitors head there to explore one of the world’s largest canyons. It could hold water from 1.7 billion Olympic-sized swimming pools! 

The Grand Canyon has long fascinated scientists. By studying its rocks, geologists have uncovered details about Earth’s history. “There’s no place in the world like it,” says geologist Wayne Ranney. 

Here are five amazing facts about the Grand Canyon.

For many people, summer means it’s time for a road trip! One popular journey is to Grand Canyon National Park in Arizona. About 6 million visitors go there every year. The Grand Canyon is one of the world’s largest canyons. It could hold enough water to fill 1.7 billion Olympic-sized swimming pools!

The Grand Canyon has long interested scientists. Geologists study its rocks. The rocks hold details about Earth’s history. “There’s no place in the world like it,” says geologist Wayne Ranney. 

Scan the canyon’s walls, and you’ll notice many rock layers of different colors. The substances that make up each layer can tell scientists about the environment in which the rocks formed.

One layer from 275 million years ago is made of sandstone, a type of sedimentary rock. That shows the region was once covered in sand dunes. Other layers are made of limestone, a sedimentary rock composed of shells from tiny sea animals. These rocks reveal that the area was under the ocean several times over millions of years.  

The oldest rocks—those at the canyon floor—are almost 2 billion years old. These dark igneous and metamorphic rocks formed inside mountains. 

Scan the canyon’s walls. You’ll notice many different colored rock layers. Their makeup tells scientists something. It reveals the environment when the rocks formed. 

One layer is from 275 million years ago! It’s made of sandstone. That’s a type of sedimentary rock. It shows the area was once covered in sand dunes. Other layers are made of limestone. That’s also a sedimentary rock. It’s made up of shells from tiny sea animals. These rocks reveal that the area was also underwater. This happened at different times over millions of years.  

The oldest rocks are found on the canyon’s floor. They’re almost 2 billion years old. They’re dark igneous and metamorphic rocks. They formed inside mountains. 

All sorts of ancient animals lived in the Grand Canyon area, from armored sea creatures to giant dragonflies. The remains are preserved as fossils in the canyon’s many rock layers.

But dinosaur fossils haven’t been found in the canyon. Why? Dinosaurs lived between 230 million and 66 million years ago. Rocks from that time have been eroded, or worn away by water and wind. The youngest rocks at the canyon’s rim are 270 million years old. 

The remains of animals that lived more recently have been found at the canyon, however. Those fossils were not hardened within rock layers but preserved inside caves. Scientists have found fossils of giant sloths that lived 11,000 years ago. The remains were in caves under hardened piles of sloth dung!

All sorts of ancient animals lived in the Grand Canyon area. They include armored sea creatures and giant dragonflies. Their remains are preserved as fossils. They’re found in the canyon’s many rock layers.

But dinosaur fossils haven’t been found in the canyon. Why? Dinosaurs lived between 230 million and 66 million years ago. Rocks from that time have been eroded. They were worn away by water and wind. The youngest rocks at the Grand Canyon are found at the rim. They are 270 million years old. 

The Grand Canyon also has remains of animals that lived more recently. Those fossils didn’t harden within rock layers. They were preserved inside caves. Scientists have found fossils of giant sloths. They lived 11,000 years ago. Their remains were buried under piles of hardened sloth dung!

The area that is now the Grand Canyon was once at sea level. Then, about 70 million years ago, tectonic plates pushed the area up from the surrounding land. Scientists think that caused groundwater to flow to the sea. 

This flowing water formed rivers. The rivers slowly eroded the layers of rock, carving a deep canyon. Then, about 6 million years ago, the rivers joined to form one long river, which was named the Colorado River. 

This river stretches from the Rocky Mountains to the Pacific Ocean. It still deepens the canyon’s floor by the thickness of a sheet of paper every year.

The area that’s now the Grand Canyon was once at sea level. Then something happened about 70 million years ago. Tectonic plates pushed the area up from the surrounding land. Scientists think that caused groundwater to flow to the sea. 

This flowing water formed rivers. The rivers slowly eroded the rock. They carved a deep canyon over time. Then the rivers joined to form one long river. It’s named the Colorado River. This happened about 6 million years ago.

This river runs from the Rocky Mountains to the Pacific Ocean. It still erodes the canyon’s floor by the thickness of a sheet of paper every year. 

Once every few years, visitors can witness a rare sight: clouds filling the canyon up to its rim! This usually happens in winter, after heavy rain or snow, on days when there’s little wind.

When a storm passes through the area, cold, moist air can sink deep into the Grand Canyon. The cold air becomes trapped beneath a layer of warmer air. When the cold and warm air meet, moisture in the warm air condenses, or turns from gas to liquid. That causes clouds to form. 

If there’s little wind, the clouds can stay trapped in the deep canyon for a day or two!

Visitors can see a rare sight every few years. Clouds fill the canyon up to its rim! This usually happens in winter. It requires heavy rain or snow and little wind.

A storm can pass through the area. Cold and moist air sinks deep into the Grand Canyon. The cold air becomes trapped under a layer of warmer air. The cold and warm air meet. Water in the warm air condenses. It turns from a gas to a liquid. That causes clouds to form. 

The clouds can stay trapped in the canyon if there’s little wind. They can last a day or two! 

After 150 years of studying the canyon, geologists still have many questions about it. For instance, they’re investigating how old parts of the canyon are. 

But that’s part of what makes this place special, says Ranney. “People like the unknown.”

Geologists still have many questions about the canyon. That’s even after 150 years of studying it! They still want to learn how old parts of the canyon are. 

But that’s part of what makes this place special, says Ranney. “People like the unknown.”