What to Learn
- Concept of rock and how it relates to the concept of mineral.
- Basic properties of the rocks: structure, mineral composition and age.
- Sedimentary rocks: formation process, occurrence, strata, major types and main examples.
- The formation of coal and petroleum.
- Igneous rocks: formation process and its determining factors, occurrence, major types and main examples.
- Metamorphic rocks: formation process and its determining factors, occurrence, major types and main examples.
- The rock cycle.
- Rocks as resources for human societies.
- Major lithological units in Spain.
Key Information
Sedimentary rocks can be made up of clasts or detritus (rock grains) weathered from other rocks by river waters, wind, coastal sea waters, glaciers, living beings, etc. This kind of sedimentary rocks are called detrital rocks.
They're classified upon the grains that they are made up of. First up, grains may be all the same size, uniform, as in a sandstone, or different sizes, as in a conglomerate. Secondly, grains may be bigger or smaller. The following table shows roughly how rock grains are classified upon their size:
| Diameter | |
|---|---|
| Clay | < 0.004 mm |
| Silt | < 0.06 mm |
| Sand | < 2 mm |
| Gravel | < 6 cm |
| Cobble | < 25 cm |
| Boulders | > 25 cm |
External Links
Excellent lesson on rocks with interactive activities and good coverage of the following topics: types of rocks, how rocks change and rock cycle.
Rock picture gallery at About.com. With photos and basic data.
Learn how to differentiate the main types of rocks at About.com.
About.com - Sedimentary rocks.
Learn the essentials of the origin, features and types of sedimentary rocks at About.com.
Learn the essentials of the origin, features and occurrence of igneous rocks at About.com.
About.com - Metamorphic rocks.
Learn the essentials of the origin, features and types of metamorphic rocks at About.com.
Movies and Animations
Rocks
An overview of the rock transformation processes on our planet.
Images
Activities