Rock Cycles, Rocks, Minerals, & Resources

1. Rock Cycles, Rocks, Minerals, & Resources Education 370 Joseph Lombardi

2. The Rock Cycle

3. The Rock Cycle • Crystallization- Molten magma cools, and solidifies within the Earth to produce igneous rocks. • Crystallization may occur either beneath the surface or, following a volcanic eruption, at the surface. • If the igneous rocks are exposed at the surface, they will undergo a process termed weathering.

4. The Rock Cycle Continued… • Weathering is defined as the disintegration and decomposition of igneous rock at or near the surface of the Earth. • The materials, or sediment that result are moved down-slope by gravity before being picked up and transported by any of a number of erosional agents- running water, glaciers, wind, or waves.

5. The Rock Cycle Continued… • Eventually these particles and dissolved substances are deposited in the ocean, river floodplains, desert basins, swamps, and dunes. • Next, the sediments undergo lithification, a term meaning “conversion into rock”. • Sediment is usually lithified into sedimentary rock when compacted by the weight of overlying layers or when cemented as percolating groundwater fills the pores with mineral matter.

6. The Rock Cycle Continued… • If the resulting sedimentary rock is buried deep within the Earth and involved in the dynamics of mountain building, or intruded by a mass of magma, it will be subjected to great pressures and/or intense heat. • The sedimentary rock will react to the changing environment and turn into metamorphic rock. • When metamorphic rock is subjected to additional pressure changes or to still higher temperatures, it will melt, creating magma, which will eventually crystallize into igneous rock.

7. Summary: The Rock Cycle • Processes driven by heat from the Earth’s interior are responsible for creating igneous and metamorphic rocks. • Weathering and erosion, external processes powered by energy from the sun, produce the sediment from which sedimentary rocks form. • Although rocks may seem to be unchanging masses, the rock cycle shows that they are not. The changes, however, take time-great amounts of time.

8. The Rock Cycle: Alternative Pathways • Igneous rocks, rather than being exposed to weathering and erosion at the Earth’s surface may remain deeply buried. • Eventually these masses may be subjected to the strong compressional forces and high temperatures associated with mountain building. • When this occurs, the igneous rocks are transformed directly into metamorphic rocks.

9. The Rock Cycle: Alternative Pathways Continued… • Metamorphic and sedimentary rocks, as well as sediment, do not always remain buried. • Rather, overlying layers may be stripped away, exposing the once buried rock. • When this happens the material is attacked by weathering processes and turned into new raw materials for sedimentary rocks.

10. The Rock Cycle

11. Earth Materials & Processes • The materials that make up the Earth are mainly rocks (including soil, sand, silt, and dust). • Rocks in turn are composed of minerals, and minerals are composed of atoms. • Processes range from those that occur rapidly to those that occur slowly.

12. Earth Materials & ProcessesContinued… • Examples of slow processes include: formation of rocks, chemical breakdown of rock to form soil (weathering), chemical cementation of sand grains together to form rocks (diagenesis), re-crystallization of rock to form a different rock (metamorphism), construction of mountain ranges (tectonism), erosion of mountain ranges.

13. Earth Materials & Processes Continued… • Examples of faster processes include: beach erosion during a storm, construction of a volcanic cone, landslides (avalanches), dust storms, mud flows.

14. Types Of Rocks

15. Types Of Rocks Continued… Igneous Sedimentary, & Metamorphic Rocks • Igneous rock is formed by the crystallization of molten magma. • Sedimentary rock is formed from the weathered products of free-existing rocks that have been transported, deposited, and lithified. • Metamorphic rock is formed by the alteration of pre-existing rock deep within the Earth (but still in solid state) by heat, pressure, and/or chemically active fluids.

16. Characteristics of Minerals • Minerals are defined as naturally occurring, inorganic crystalline solids that possess a definite chemical structure. • Minerals are the building blocks of rocks.

17. Properties of Minerals • Crystal form: The external appearance of a mineral as determined by its internal arrangement of atoms. • Luster: Luster is the appearance or quality of light reflected from the surface of a mineral. • Color.

18. Properties of Minerals Continued… • Streak: The color of a mineral in its powdered form. • Hardness: The resistance a mineral offers to scratching. • Cleavage: The tendency of a mineral to break along planes of weak bonding.

19. Mohs Scale of Mineral Hardness

20. Mineral Groups • Minerals can be classified into groups depending upon their chemical composition.

21. Relative Abundance Of The Most Common Elements In The Earth’s Crust • Oxygen (O) 46.6%, Silicon (Si) 27.7%, Aluminum (Al) 8.1%, Iron (Fe) 5.0%, Calcium (Ca) 3.6%, Sodium (Na) 2.8%, Potassium (K) 2.6%, Magnesium (Mg) 2.1%, All others 1.7%.

22. Mineral Groups Continued… • The largest group of rock forming minerals is the silicate group. • All silicate minerals contain silicon and oxygen. • Some examples of silicate minerals are olivine, augite hornblende, garnet, biotite, albite, and quartz. • Silicates are the most common minerals because most of the Earth’s crust is made of silicon and oxygen.

23. Mineral Groups Continued… • Non-silicate minerals are those that do not contain silicon and oxygen. • There are five groups of non-silicates: oxides, sulfides, halides, carbonates and sulfates.

24. Mineral Groups Continued… Oxides • Oxides are minerals that form when an element combines with oxygen. • Some examples of oxides are corundum, hematite, and magnetite.

25. Mineral Groups Continued… Sulfides • Sulfides are minerals that form from compounds that contain sulfur. • Some examples of sulfides are galena and pyrite.

26. Mineral Groups Continued… Halides • Halides are minerals that form when certain elements combine with the Halogen Group from the periodic table. • The halogen group includes chlorine, bromine, fluorine, and iodine. • Some examples of halides are halite and fluorite.

27. Mineral Groups Continued… Carbonates • Carbonates are minerals that contain a carbon atom surrounded by three oxygen atoms (carbonate ion). • Some minerals that contain this ion are azurite, aragonite, and malachite.

28. Mineral Groups Continued… Sulfates • Sulfates are minerals that contain a sulfur atom surrounded by four oxygen atoms (sulfate ion). • Some minerals that contain this ion are gypsum, celestite, and barite.

29. Mineral Resources • Mineral resources are the Earth’s storehouse of useful minerals that can be recovered for use. • Resources include already identified deposits from which minerals can be extracted profitably, called reserves, as well as well known deposits that are not yet recoverable under present economic conditions or technology. • Deposits inferred to exist, but not yet discovered, are also considered as mineral resources.

30. Mineral Resources Continued… • There three principal categories for mineral uses are: rock forming, economic, gems and ornamentals. • Rock forming refers to the primary function or use of some minerals. • Many minerals have commercial or economic use. Some minerals are considered ore minerals (e.g. hematite – iron ore), while others are common commercial products (e.g. calcite – cement).

31. Mineral Resources Continued… • Common gemstones used in jewelry are actually minerals. Examples are diamonds, garnet, and amethyst. • Large mineral specimens can also be used for decorative or ornamental purposes. Examples are pyrite (fool’s gold), or geodes lined with quartz or amethyst crystals.

32. Mineral Resources Continued… • Recall that more than 98% of the Earth’s crust is composed of only eight elements. • Except for oxygen and silicon, all other elements make up a relatively small fraction of common crustal rocks. Indeed, the natural concentrations of many elements are exceedingly small.

33. Mineral Resources Continued… • A deposit containing only the average crustal percentage of a valuable element like gold is worthless if the cost of extracting it greatly exceeds the value of the material recovered. • To be considered of value, an element must be concentrated above the level of its average crustal abundance.

34. Mineral Resources Continued… • Examples of minerals and their economic use: Hematite (oxides) ore of iron, Galena (sulfides) ore of lead, Gypsum (sulfates) plaster, Gold (native elements) trade and jewelry, Fluorite (halides) used in steel making, and Calcite (carbonates) Portland cement and lime.

35. Works Cited • 1.) The Mineral Gallery • http://minerals.galleries.com/default.html • 2.) Minerals • http://www.tulane.edu/~sanelson/geol111/minerals.html • 3.) Rock Cycle Images http://rst.gsfc.nasa.gov/Sect2/Sect2_1a.html

36. Works Cited Continued… • 4.) Tarbuck, Edward J., Lutgens, Frederick K. Earth Science 8th Ed. 1997 New Jersey: Prentice Hall Inc. • 5.) Image- silicon-oxygen tetrahedron http://www.msdwc.k12.in.us/msdclass/WENJ