Book 16, Question 15
How Can Salt Break a Rock?
Salt can break a rock by growing crystals inside its tiny cracks! Rainwater or groundwater that seeps into rocks carries dissolved salt. When the water dries up, the salt crystals are left behind and push outward.
More fun facts
- Growing crystals, like salt or ice, push hard enough to crack rock and pop off tiny grains.
- At Scotts Bluff in Nebraska, salt crystals grow right on the rock surface.
- The salts there include sodium chloride, which is like table salt, and calcium sulfate.
- Water seeping through the rock carries dissolved salt to the surface, and the salt crystallizes when the water evaporates.
- Salt can build up in sheltered hollows, slowly making holes called tafoni or honeycomb weathering.
- Tafoni often look like a sponge or Swiss cheese, and you can see them in Arches and Capitol Reef national parks.
Sources: National Park Service, National Park Service, National Park Service
Questions kids ask
Why does salt damage rock more in dry places?
Dry air makes water evaporate fast, so salt crystals form again and again inside the rock.