The Big Hole in Arizona

Arizona is a state in the western United States of America. About 6.4 million people live in Arizona, which covers an area almost as large as Germany. About a quarter of Arizona's population lives in its largest city, Phoenix.

Arizona has some amazing natural wonders. The best known is surely the Grand Canyon in the north. Over many millions of years, the Colorado River has carved a deep gorge into the rock. The gorge is about 450 km long, up to 30 km wide and 1,800 m deep.

Every year, many people also visit Verde Valley and Monument Valley to admire the rust-red rocks. In another national park, you can see petrified tree trunks. They sank into the sea more than 200 million years ago, became fossilized beneath sand and silt, and later re-emerged.

And then there is a huge, deep hole in Arizona. It is about 70 km east of the city of Flagstaff. It is about 180 m deep and 1,200 m in diameter. It is surrounded by a rim that rises up to 60 m above the surrounding terrain. It is a crater. A crater is a depression in the Earth’s surface caused by a volcano or the impact of a celestial body. The crater in Arizona is known as Barringer Crater or Meteor Crater.

It was formed about 50,000 years ago. At that time, a meteorite struck here at enormous speed and with tremendous force. It is thought to have been 50 m in diameter and to have weighed around 300,000 tonnes. It is estimated to have hit the Earth at a speed of 55,000 to 100,000 km/h.

The impact caused a powerful earthquake. All life within a radius of several kilometres was wiped out, and a gigantic fireball spread out. Rocks 30 m thick were hurled high into the air, and a shock wave caused a storm that could still be felt 40 km away.

More than 100 years ago, engineer Daniel Barringer bought the land and began studying the crater. He hoped to extract large quantities of iron because the meteorite that landed here was made mostly of iron. Barringer tried his luck for 27 years, but found only a few fragments.

Today we know that the meteorite had almost completely vaporized. The largest fragment can be seen in a small museum. American astronauts practised their Moon landings in the crater. There are many craters on the Moon too, caused by meteorite impacts.

But what are these celestial bodies that collide with Earth and the Moon?

Our Sun is orbited by 8 large planets and several dwarf planets. Many smaller celestial bodies also travel in orbits around the Sun. The larger ones are called asteroids, the smaller ones comets and meteoroids. There are many millions of them.

Compared with the planets, they are very small. Some are only a few centimetres in diameter, while others are more than 100 kilometres across. Small fragments hit the Earth every day. We usually see them as shooting stars. A celestial body burns up when it enters the Earth’s atmosphere. At most, only small fragments reach the ground. Scientists call meteoroids that burn up in the Earth’s atmosphere meteors.

There is a lot of space in our solar system. That is why a large asteroid or meteoroid very rarely hits Earth. When one does, however, it can cause enormous destruction.