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What is a rock?

What is a rock?. A rock is a mixture of minerals and other materials. . Formation of rocks. Igneous: about 150 rocks. Metamorphic – about 300 rocks. Sedimentary –about 50 rocks. Rocks are categorized by how they were formed. Classifying Rocks. Mineral Composition. Color. Texture.

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What is a rock?

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  1. What is a rock? A rock is a mixture of minerals and other materials.

  2. Formation of rocks Igneous:about 150 rocks Metamorphic – about 300 rocks Sedimentary–about 50 rocks Rocks are categorized by how they were formed.

  3. Classifying Rocks Mineral Composition Color Texture Using these properties, Geologists can classify a rock according to its origin – or how the rock formed.

  4. Texture Texture – Rocks are made of particles of other minerals called grains.

  5. IN SUMMARY… • Geologists classify rocks into 3 major groups: • Igneous rock: from cooled magma/lava • Sedimentary rock: from weathered sediment compressed • Metamorphic rock: existing rock changed from heat/pressure (forms underground) • When studying a rock sample, geologists observe the rock’s: • Mineral composition: can be 1 or many more that make up a rock • Color: lightness/darkness • Texture: Grain size, grain shape, grain pattern

  6. Igneous rocks Forms from magma or lava

  7. Classifying igneous rocksby origin They are either intrusive(formed beneath surface) or extrusive (formed above Earth’s surface) Basalt rock

  8. Classifying igneous rocksby texture Rhyolite - extrusive Granite - Intrusive

  9. Classifying igneous rocksby MINERAL COMPOSITION Mineral composition of Granite • Uses of Igneous Rocks • Granite - For buildings & monuments – Egyptians used for statues over 3,500 years ago. • Basalt – crushed for gravel in construction. • Pumice – used for polishing. • Obsidian – used for ancient tools.

  10. Mineral composition Feldspar – 63% Quartz – 27% Mica & Hornblende – 10%

  11. In summary… • Igneous rocks ALL were formed from magma or lava • They are classified by origin, texture and mineral composition • They may form ON or BENEATH Earth’s surface • Extrusive rock: From lava on the surface • Intrusive rock: From magma that hardened under the surface • Since they are hard, dense and durable they have been used for tools and building materials.

  12. Sedimentary Rocks Sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, and cementation.

  13. Types of Sedimentary Rocks Clastic – particles are squeezed together. Shale Sandstone Conglomerate Organic – remains of plants and animals. coal limestone Chemical – solutions evaporating Rock salt

  14. In summary… • Sediment is small, solid pieces of material that come from rocks or living things • Series of processes: Erosion (water/wind), deposition (sediment lands somewhere), compaction (presses sediment together with weight/pressure), cementation (dissolved minerals crystallize and glue particles of sediment together) • Clastic rocks: formed when rock fragments squeezed together (sandstone) • Organic rocks: remain of plants/animals deposited in thick layers. (coal) • Chemical rocks: minerals dissolved in a solution crystallize (limestone)

  15. Metamorphic Rocks Heat and pressure deep beneath Earth’s surface can change any rock into metamorphic rock.

  16. Foliated vs. nonfoliated • Two categories • foliated: grains arranged in parallel layers or bands • non-foliated: mineral grains arranged randomly.

  17. Important concepts • Heat and pressure DEEP beneath Earth’s surface can change ANY rock to a metamorphic rock. • When changed into metamorphic rock it changes its appearance, texture, crystal structure and mineral content • High temperatures/pressure can change minerals into other minerals! • Metamorphic rock classified by the arrangement of grains that make up the rock • Parallel layers : foliated • Random grains: nonfoliated • Used for building and sculpture ( marble/slate) • Marble formed from limestone subjected to heat/pressure below Earth’s surface

  18. The rock cycle • Energy is continuously used and recycled as rocks go through the rock cycle.

  19. Important concepts • Rocks are continuously built, destroyed and changed in the crust. • Example: • Igneous rock granite formed beneath surface • Forces of mountain building push granite upward (forming mountain) • Slowly, water/wind wear away granite • Granite particles become sand, carried by streams to the ocean • Over millions of years sandy layers pile up on ocean floor • Slowly, sediment changes to sandstone (sedimentary rock) • Over time, sandstone is buried • Heat/pressure change rock’s texture • Sandstone changed into metamorphic rock : quartzite

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