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Earth science Rock cycle, Igneous rocks. 6.1 The Rock Cycle Rock- a group of minerals bound together in some way Can consist of one mineral, but usually.

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Presentation on theme: "Earth science Rock cycle, Igneous rocks. 6.1 The Rock Cycle Rock- a group of minerals bound together in some way Can consist of one mineral, but usually."— Presentation transcript:

1 Earth science Rock cycle, Igneous rocks

2 6.1 The Rock Cycle Rock- a group of minerals bound together in some way Can consist of one mineral, but usually multiple minerals Rocks form from other rocks This relationship is seen in the rock cycle (p 119)


4 Types of Rocks 1.Igneous- formed by the cooling and hardening of magma (hot molten rock) 2.Sedimentary- formed by the compaction and cementation of sediment (rock fragments, plant remains& minerals that have settled out of solution) 3.Metamorphic- formed from the effect of heat and pressure on preexisting rocks

5 6.2 Igneous Rocks Categorized by composition, then texture Texture is caused by cooling environment

6 Magma/ Rocks with Felsic Composition Thick and slow moving magma Cooler (though still very hot) Large amounts of silica Light colored rocks Violent eruptions- builds up pressure Mt. St. Helens (actually closer to intermediate, but close enough)


8 Magma/ Rocks with Mafic Composition Thinner, faster moving magma Hotter Large amounts of Fe & Mg, little Si Dark colored rocks (ferromagnesian silicates) Calm eruptions- releases pressure often Hawaii


10 Textures- Extrusive (aka Volcanic) Cools above the ground, very quickly Small crystals, microscopic crystals or no crystallization (not crystalline is not a mineral, has glassy texture- obsidian) Pumice is created when gas bubbles are “frozen” into quickly cooling rock

11 Obsidian

12 Texture: Intrusive (Plutonic) Cools below the surface very slowly Large crystals Other texture: porphyry- cools below ground, then ejected and cools fast- has large crystals surrounded by small ones


14 Igneous Rock Families By composition, members have differing textures 1.Granite family- felsic, fine grained is rhyolite, coarse is granite 2.Gabbro family- mafic, fine- basalt, coarse is gabbro 3.Diorite family- intermediate, fine- andesite, coarse- diorite 4.Ultramafic

15 Granite & Rhyolite

16 Gabbro & Basalt

17 Diorite & Andesite

18 Ultramafic- Peridotite

19 Plutons (taken from 6.2) A rock mass that forms when magma cools inside Earth’s interior 1.Batholith 2.Laccolith 3.Stock 4.Sill 5.Dike


21 6.3 Sedimentary Rocks 3 main types of sedimentary rocks: 1.Clastic- formed from fragments of other rocks (sediment) 2.Chemical- Form when minerals precipitate (fall out) of solution 3.Organic- Forms from sediments consisting of the remains of plants and animals

22 Clastic

23 Chemical

24 Organic

25 Clastic Sedimentary Rocks Sediment size (large to small): Boulder, Cobble, Pebbles, Gravel, Sand, Silt, Clay Eroded and deposited by running water Larger sizes are first to be deposited, near shore, smaller particles such as sand, silt and clay are deposited further off shore (p 127) Once sediment is deposited it must be cemented

26 Boulders

27 Pebbles

28 Sand

29 Cementation Once sediment is deposited it must be cemented Cementation- the binding of loose sediment by minerals filling the space between grains Silica (SiO2), Calcite (CaCO3) and Iron oxide/ hematite can act as cements

30 Cement

31 Clastic Sedimentary Rocks 1. Conglomerate- rounded coarse sand and pebbles are cemented together 2.Breccia- similar to conglomerate, but particles are angular 3.Sandstone- sand is cemented 4.Shale- made of clay- often breaks in sheets

32 Conglomerate

33 Breccia

34 Sandstone

35 Shale

36 Chemical Sedimentary Rocks 1.Rock salt- halite 2.Rock gypsum 3.Limestone- can be any color, fine grained, calcite (will fizz in acid) 4.Dolostone- similar to limestone, but made of dolomite (will not fizz in acid)

37 Rock Salt

38 Gypsum

39 Limestone

40 Dolostone

41 Organic Sedimentary Rocks 1.Bituminous coal- plant remains 2.Limestone- formed from the shells of clams, corals and some algae (calcite was taken from chemical limestone) a. chalk b. coquina- made completely of shells

42 Bituminous Coal

43 Organic Limestone

44 Chalk

45 Coquina (limestone)

46 Sedimentary Rock Features 1.Stratification- arrangement of layers of different sediment 2.Bedding plane-plane between layers, usually horizontal, but sometimes cross bedding occurs 3. Fossils- the remains, impression or any other evidence of a plant preserved in rock 4. Ripple marks- sand patterns due to wind, wave, stream or current action

47 Stratification

48 Ginko Fossil

49 Sedimentary Rock Features 5. Mud cracks- form when mud dries 6. Nodules- lumps of silica in limestones 7. Concretion- lump of calcite in shale 8. Geodes- hallow lumps of silica in limestone, often have crystals inside

50 Mud Cracks

51 Nodules

52 Concretion

53 Geode

54 6.4 Metamorphic Rocks Metamorphism- the process by which a rock’s structure is changed by pressure, heat and moisture Metamorphic rocks: Formed from preexisting rocks called parent rocks Often resemble their parent


56 Metamorphic Rocks Minerals may be enlarged, re-formed or new minerals may appear Pressure forces grains together, making rocks less porous (less space between grains)


58 2 Types of Metamorphism 1.Regional- occurs during mountain building events Large areas experience heat and pressure 2. Local- effects much smaller area, 2 subtypes: a.Contact- igneous rock bakes surrounding rock b.Deformation- stress& friction, at faults

59 Rock Descriptions Identification is often based on parent rock, mineral content and texture Foliation- the tendency of metamorphic rocks to form bands of minerals or split along parallel layers

60 Metamorphic Rock Types 1. Quartzite- parent rock is sandstone (a sedimentary rock made of sand sized quartz sediment), much more dense than sandstone 2. Marble- parent- limestone (a sedimentary rock made of calcite- fizzes in acid), impurities show as wavy lines, usually fine grained with a sugary texture

61 Metamorphic Rock Types 2 3. Shale series- shale is a sedimentary rock made of clay sized sediment (very small)- all foliated Shale  Slate  Phyllite  Schist  Gneiss


63 Shale Series A. Slate- lowest metamorphism- foliated layers, mineral grains usually cannot be identified B. Phyllite- similar to slate, but is usually shiny due to mica grains becoming larger C. Schist- can also be parented by basalt, mineral grains are usually much larger D. Gneiss- parents can include shale, granite and conglomerate- high grade metamorphism, has a banded appearance

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