1. Rocks Part II

2. Three Different Types of Rocks Sedimentary – Rock produced by cemented mineral particles deposited by wind, water, ice, or chemical reactions. Igneous –Rock produced by the cooling of magma (melted rock). Metamorphic – Rock that has undergone change as a result of intense heat or pressure.

3. Sedimentary Rock Made from deposits of minerals Lithification – The process by which small particles are compressed in larger ones

4. More Sedimentary rocks Compactation – Particles are compacted into smaller spaces Drying and Crystallization are other ways of forming sedimentary rocks Cementation occurs when minerals fill in the spaces between larger particles and cement the pieces together

5. Types of Sedimentary Rocks Clastic Chemical /Evaporation Organic

6. Clastic Sedimentary Rock Made of broken pieces of rock Can be large chunks, jagged pieces of rock, and pebbles. Can also be sand, silt, and clay.

7. How Clastic Rocks Are Made Rocks are broken by the action of erosion. Some are flushed into a river or stream. As the water slows down, it drops some of the particles it’s carrying. The largest particles drop first, followed by the next largest down to the silt and clay. This is called sorting.

8. Types of Clastic Rocks Conglomerates – Made with a mixture of large and small pebbles Breccias – Made from smaller and more angular and jagged particles Conglomerate rock Breccias Rock

9. Clastic Rocks Con’t Sandstone – Stone made from deposited sand Shale – Rock made from deposited clay. Sandstone Shale

10. Chemical Formation of Sedimentary Rocks Formed many ways Evaporation –Formed by the evaporation of water (usually seawater) Precipitation –Formed by a chemical reaction that pulls a solid out of a solution

11. Types of Evaporation Rock Gypsum –CaSO 4 2H 2 O –Used to make drywall Rock Salt –NaCl –Used in cooking, ice melting, cleaning, ect. Gypsum Rock Bonneville Salt Flats Rock Salt (NaCl)

12. Organic Sedimentary Rock These rocks are formed from dead plants and animals. The first is coal made from compressed plants. The second is limestone made from compressed shells and animals that died and settled to the bottom of the ocean.

13. Minerals There are 3000 different minerals Only 20 are common Native minerals are pure and often rare

14. Silicates 90% of all the Earth’s elements are silicates Quartz is the most abundant Composed of silicon and oxygen

15. Non-silicates Less than 10% of the Earth’s minerals There are many families Some are composed of only one element- these are the native elements like gold, silver, copper, iron

16. Identifying Minerals 1.Color- not dependable 2.Luster- how the mineral reflects light 3.Streak- powder left when rubbed on a rough surface 4.Crystal shape- how the molecules are arranged

17. Identifying minerals continued.. 1.Hardness- using Mohs’ 1-10 scale 2.Cleavage and fracture- how a mineral breaks (smooth or rough and jagged) 3.Special properties- radioactive, glowing, double refraction, etc.

18. Earth’s Geological History Piecing together geological history is difficult Plates are always moving and breaking apart Weathering and erosion wear away evidence

19. Records of Change Fossils Uniformitarianism Superposition Relative dating Numerical dating

20. FOSSILS TELL WHERE A ROCK WAS FORMED AND WHAT THE ENVIRONMENT WAS LIKE LAYERS OF ROCK THAT HAVE THE SAME ROCKS AND FOSSILS ARE THE SAME GEOLOGIC AGE

21. UNIFORMITY THE BASIC UNDERLYING PRINCIPLE FOR GEOLOGICAL PROCESSES SIMILAR PROCESSES PRODUCE SIMILAR RESULTS EXAMPLE: SEDIMENTS ALWAYS SETTLE IN SIMILAR WAYS REGARDLESS OF WHERE OR WHEN

22. Superposition Simply states that younger rock layers lie on top of older rock layers

23. Relative Dating Using the law of superposition, scientists can determine the “relative age” of a rock by where it falls in the layers This is NOT an exact age

24. Numerical Dating Known as absolute dating The process of estimating the age of rocks using radioactive decay or half-life. This does not give an exact age of a rock

25. Beyond Weathering! After rocks are broken down over and over, they are small enough to become part of a vital resource known as soil. The main ingredients in soil are water, air, rock, and organic material.

26. The Layers Soil is what covers much of our Earth’s land. It allows plants to grow so they can provide consumers with necessary energy. As plants and animals die, they decompose and mix with the already weathered sediments. This creates humus a rich layer found at the top of soil. The next layer is the subsoil. It is made of larger pieces of rock and minerals with little or no humus. Below the subsoil is the last layer known as the bedrock (parent rock). This is the solid rock layer that sits on top of the convecting magma.

27. Surface Changes Weathering and soil formation are continuously happening due to erosion by wind, water, changing temperatures, and other natural forces. In addition to these natural forces, we as humans can play a huge role in changing Earth’s surface. We remove plants exposing rich topsoil to the elements, we overuse the soil when growing crops depleting it of rich nutrients, we strip mine the surface for mineral resources, and we blast away surfaces to build roads and structures for our benefit.