Caliche dirt, also known as caliche, is primarily found in arid and semi-arid regions with a seasonal rainfall pattern. Here's a breakdown of the typical locations:

* Southwestern United States: Arizona, New Mexico, Texas, and California.

* Mexico: Particularly in the northern and central regions.

* South America: Parts of Argentina, Chile, and Bolivia.

* Australia: Areas in the outback.

* Other arid regions: The Middle East, Africa, and parts of Asia.

Why these regions?

Caliche forms through a complex process involving:

* Evaporation: High evaporation rates in these arid environments lead to the concentration of dissolved minerals in the soil.

* Groundwater: Fluctuating groundwater levels cause minerals to precipitate and solidify within the soil.

* Calcium Carbonate: Caliche is mainly composed of calcium carbonate (CaCO3), which is abundant in these regions.

Specific Locations:

* Desert landscapes: Caliche is commonly found in deserts, especially in areas with alluvial fans, playas, and washes.

* Dry grasslands and savannas: Caliche can also be found in these areas, particularly where there are shallow soils and fluctuating groundwater levels.

Note: Caliche is not always a uniform layer. It can be found in patches or as hardpan layers, which can hinder plant growth and make construction difficult.