Weathering

Weathering is the process of breaking rocks into smaller pieces. It happens slowly over time. Water, ice, wind, plants, and chemicals all cause weathering. Weathering does not move the broken pieces. It just breaks them apart where they are.

Physical Weathering

Physical weathering breaks rocks without changing what they are made of. Water seeps into cracks in rocks and freezes. When water freezes, it expands and pushes the crack open wider. Plant roots also grow into rock cracks and split them apart. Over time, big rocks break into smaller and smaller pieces.

Chemical Weathering

Chemical weathering changes the minerals inside rocks. Rainwater is slightly acidic and can slowly dissolve certain rocks like limestone. Oxygen in the air reacts with iron in rocks and creates rust. Chemical weathering is faster in warm, wet climates. It is one reason old statues and buildings slowly wear away.

Fun Facts

• The Grand Canyon was carved by millions of years of weathering and erosion by the Colorado River.
• Acid rain caused by pollution speeds up chemical weathering on buildings and statues.
• Even the hardest rock, diamond, can be weathered over very long periods of time.

Did You Know?

The famous faces carved on Mount Rushmore are weathering away at a rate of about one inch every 10,000 years. Park workers seal cracks each year to slow down the process!