Why is tropical red earth red?

Answer 1

The iron in the soil turns red when exposed to oxygen (oxidation). Although iron is common is most soils, oxidation (rusting) is much more pronounced in hot and wet climates.

Answer 2

Tropical red earth gets its red color from the presence of iron oxide minerals, such as hematite and goethite. These minerals are formed through weathering processes that oxidize iron-rich minerals in the soil, giving it a characteristic red hue.