- Slides: 34
Rocks THE ROCK CYCLE CLASSIFYING ROCKS
What is a rock? A group of minerals bound together in some way.
The Rock Cycle A series of processes above/below the Earth that change rocks from one kind to another over time! Can follow various paths The food web of geology!
3 main types of rocks 1) Igneous -formed by… 2) Sedimentary- formed by erosion, pressure of layers of sediments 3) Metamorphic- formed by heat/pressure over time. Molten rock- formed by melting https: //www. youtube. com/watch? v=6 bky. Xv. YP 4 j. M
How do we classify rocks? Color Texture Mineral composition (remember minerals make up rocks)
Texture Size, shape and pattern of the rock grains (particles of minerals) Smooth/glassy Rough/chalky
Grain size Large- easy to see ? (course grains) Small- fine grained
Grain shape Round? Jagged? Stars? Stripes?
Grain pattern Flat (like a pancake) Wavy/swirling Bands
No visible grain? In this case it means the rock cooled quickly! It probably has a smooth/shiny texture like glass…
Mineral composition Look at the size/shape of crystals Coloration
Origin Can you identify which of the three major types of rocks it is?
https: //www. youtube. com/watch? v=a. SLs 2 ek 6 Azs https: //www. youtube. com/watch? v=2 RZMXd 4 IAb 0
Igneous Rocks that formed from magma/lava “fire” Most have mineral crystals Hard, dense, durable rocks https: //www. youtube. com/watch? v=Pr. N 7 jygu 4 c. Q
Igneous rocks are used for
2 origins of igneous rocks 1) Extrusive/Volcanic – from lava Forms outside of the volcano on the surface. Example- basalt 2) Intrusive/Plutonic- forms from magma cooling below surface Continents and mountain ranges can be intrusive Example- granite
Texture of igneous rocks Texture can vary Rapid cooling (small crystal structures, fine grains) Slow cooling (large crystals, course grains)
Mineral composition of igneous rocks Silica Amount of silica present can determine color of igneous rocks
Let’s look at igneous rocks!
Sedimentary Rocks Form from particles (sediment) deposited from water and wind. https: //www. youtube. com/watch? v=NX 0 k. Po 2 m. MC 4 https: //www. youtube. com/watch? v=04 a_32 Nu. Yqs
Process of sediment to rock… 1) Erosion- water/wind or other forces carry away rock fragments. 2) Deposition- sediment is eventually separated or “deposited. ” 3) Compaction- sediment is crushed or pressed together 4) Cementation- dissolved minerals crystalize and glue together (forming a rock)
3 major types of sedimentary rocks 1) Clastic- formed from rock fragments being squeezed together. Organized by size of grain/size of fragments. Examples: Shale- forms from clay, often soft, splits into flat pieces Sandstone- feels gritty, forms from sand, contains quartz Conglomerate and Breccia- rocks within rocks, vary in size. Look for shape of rocks within (round- conglomerate, jagged- breccia
Organic rocks- formed from plant/animal remains. Were once “living. ” Examples: Coal- remains of swamp plants buried in mud/water. Limestone- shells of animal remains (calcite) pile up and cement together. (Not all limestone has visible shells and skeletons). Compact and shell limestone. Chalk- is another form of limestone. Chert/Flint- sharp edges, used for tools
Chemical rocks- form from minerals being dissolved in solutions and crystallizing. Can form from evaporation of liquid. Examples: Halite (rock salt) Gypsum-
Uses of sedimentary rocks https: //www. youtube. com/watch? v=W 4 a 3 Az. DYm 2 M
Metamorphic rocks Meta “change” Morphosis “form” Formed from heat and pressure Can form from igneous, sedimentary or from other metamorphic rocks. https: //www. youtube. com/watch? v=Uuzmub 5 PXNQ
Classifying metamorphic rocks Heat can change the crystal size and shape of mineral grains Pressure can rearrange the organization of minerals Rocks that have parallel grains are “foliated”
Uses of metamorphic rock Marble Slate
Weathering/Erosion of Rocks https: //www. youtube. com/watch? v=p 2 X 4 U 1 m. Qzo. E&list=PLXR _Ht. DPvlm 8 tv. Sb. WQVw. EKBd. Lm. Fbp. Bh. MV https: //www. youtube. com/watch? v=o. Fnpm 4 SUF 7 I&index=2&l ist=PLXR_Ht. DPvlm 8 tv. Sb. WQVw. EKBd. Lm. Fbp. Bh. MV
Weathering Process that breaks down rocks and other substances over time. Water, wind, heat, cold, salt, and ice can weather materials.
Erosion Movement of rock particles (sediment) by wind, water, ice or gravity. Works with weathering Slow process https: //www. youtube. com/watch? v=ktf 73 HNZZGY&list=PLXR_ Ht. DPvlm 8 tv. Sb. WQVw. EKBd. Lm. Fbp. Bh. MV&index=4
Mechanical Weathering Physical breakdown of rocks (cracking, peeling) Freezing/Thawing Pressure Animals breaking apart Sediment has similar chemical composition as original rock.
Chemical Weathering Breaks down rock through chemical changes/reactions Acid rain, water, oxygen, carbon dioxide Sediment has a different chemical composition than original rock
Factors that influence weathering 1) Climate Wet climates weather faster High temperature increases weathering 2) Type of rock Minerals in rock determine how fast it weathers Are they water soluble? Permeable?