Caliche

Caliche is a type of soil that is very hard and often found in arid regions. Imagine if you took a container and filled it with sand, then poured a lot of water in it and let it sit in the sun for a long time. The sun would dry the water out, but the sand would stick together because the water left behind minerals and salts that act like glue.

Caliche is kind of like this. Over a long time, rainwater soaks into the ground, picking up minerals and salts. When the water evaporates, it leaves behind these minerals and salts. Over time, enough of these minerals and salts accumulate in the soil to make it super hard and almost like rock.

People who live in areas with a lot of caliche have to work extra hard to grow plants because it's difficult for roots to push through. But people also use caliche for building things like walls or even houses because it's so tough.