Forces of Change

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Chip Off the Old Block
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Soils “inherit” minerals as “parent” rocks weather, or break down, into particles.

The types and proportions of mineral particles present in a soil affect its color and texture.

Ninety-eight percent of the Earth’s crust is made of just eight elements—oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium. Minerals are combinations of these (and other) elements. Rocks are hardened mixtures of minerals.

Parent rock
Parent rock magnified
100 times
Edward Vicenzi, Smithsonian Institution
Rotten rock
Rotten rock magnified
50 times
Rotten rocks begin to form secondary minerals, such as silicate clay and iron oxide, when primary minerals dissolve and re-form as new particles.
Robert C. Graham, University of California, Riverside
Soil
Soil magnified 50 times
Robert C. Graham, University of California, Riverside
Parent Rock
Parent rock magnified
100 times
Parent rocks are entirely primary minerals, such as quartz, mica, and feldspar, that have not changed chemically since they first crystallized.
Edward Vicenzi, Smithsonian Institution
Rotten Rock
Rotten rock magnified
50 times
Rotten rocks begin to form secondary minerals, such as silicate clay and iron oxide, when primary minerals dissolve and re-form as new particles.
Robert C. Graham, University of California, Riverside
Soil
Soil magnified 50 times
The oldest soils are the most highly weathered, are rich in secondary minerals, and have many spaces filled with air or water (blue areas in photo).
Robert C. Graham, University of California, Riverside