Earth science Rock cycle, Igneous rocks

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 • Igneous- formed by the cooling and hardening of magma (hot molten rock) • Sedimentary- formed by the compaction and cementation of sediment (rock fragments, plant remains& minerals that have settled out of solution) • 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 • Granite family- felsic, fine grained is rhyolite, coarse is granite • Gabbro family- mafic, fine- basalt, coarse is gabbro • Diorite family- intermediate, fine- andesite, coarse- diorite • 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 • Batholith • Laccolith • Stock • Sill • Dike

21. 6.3 Sedimentary Rocks • 3 main types of sedimentary rocks: • Clastic- formed from fragments of other rocks (sediment) • Chemical- Form when minerals precipitate (fall out) of solution • 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 • Conglomerate- rounded coarse sand and pebbles are cemented together • Breccia- similar to conglomerate, but particles are angular • Sandstone- sand is cemented • Shale- made of clay- often breaks in sheets

32. Conglomerate

33. Breccia

34. Sandstone

35. Shale

36. Chemical Sedimentary Rocks • Rock salt- halite • Rock gypsum • Limestone- can be any color, fine grained, calcite (will fizz in acid) • 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 • Bituminous coal- plant remains • 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 • Stratification- arrangement of layers of different sediment • Bedding plane-plane between layers, usually horizontal, but sometimes cross bedding occurs • Fossils- the remains, impression or any other evidence of a plant preserved in rock • 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