Water makes up nearly three-quarters of the Earth’s surface, but it does more than just cover our planet—it also plays a vital role in shaping it.
Consider the Grand Canyon. Measuring 277 miles long, 18 miles wide and more than 1 mile deep, it is considered one of the Seven Natural Wonders of the World and attracts more than 5 million visitors per year. This geological marvel was created by the waters of the Colorado River through the processes of weathering and erosion.
Weathering is the process by which moving water breaks down soil, rock and minerals, and erosion is the process by which the flowing water transports soil and rock from one spot and deposits it elsewhere. The two processes often occur in conjunction.
Weathering and erosion are very slow processes. Geologists believe the Colorado River has been flowing through the Grand Canyon for at least 17 million years, and it has been gradually shaping the canyon this entire time. The flowing water of the river and its tributaries has carved away at the rock of the Colorado Plateau, creating the sight we are familiar with today.
Caves and caverns are another example of weathering and erosion. Limestone caves, such as the Carlsbad Caverns in New Mexico, are formed when rainwater mixes with carbon dioxide in the ground and wears away at the limestone. Sea caves, which can be found along coastlines, are formed when powerful waves crash against the shore and break away chunks of rock. Ice caves are formed when glaciers melt and the ice melt flows across the ground as a stream.
You don’t have to travel very far to see the effects of weathering and erosion for yourself, though. If you’ve ever been to the beach, you’ve already seen evidence of how powerful of a force moving water can be — and all you had to do was look down. The sand covering the beach is actually the result of rocks being broken down into tiny pieces and then washed ashore by the waves.
Although weathering and erosion are responsible for creating beautiful sights such as sandy beaches and the Grand Canyon, there are many negative consequences as well. Landslides are some of the most dangerous side effects of erosion. When hillsides or mountainsides are gradually worn away, they can become unstable and break down, especially when triggered by extreme weather such as floods, heavy rain or snow. Every year, landslides cause massive amounts of property damage and casualties.
1. What are the processes by which water can shape the Earth?
2. What does the author describe in the passage?
3. How does the author present the Grand Canyon?
4. In the last paragraph, the author mentions landslides to make the point that erosion ________.
