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Chapter 3. What is a Rock? A mixture of minerals, mineraloids, glass, or organic matter ex. Granite = mica + quartz + feldspar + hornblende + other minerals.

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Presentation on theme: "Chapter 3. What is a Rock? A mixture of minerals, mineraloids, glass, or organic matter ex. Granite = mica + quartz + feldspar + hornblende + other minerals."— Presentation transcript:

1 Chapter 3

2 What is a Rock? A mixture of minerals, mineraloids, glass, or organic matter ex. Granite = mica + quartz + feldspar + hornblende + other minerals

3 3 Rock Types Igneous Rocks – form from cooling magma or lava Metamorphic Rocks – form from extreme heat and pressure Sedimentary Rocks – form from the compaction and cementation of sediment (rock fragments)

4 Other Key Terms Magma: molten rock inside the Earth Lava: molten rock on the surface of the Earth Sediment: smaller pieces of rock (rock fragments) Weathering: breaking rocks into sediment Erosion: moving sediment from one location to another Compaction and Cementation: process of squeezing and gluing sediment into a sedimentary rock

5 The Rock Cycle

6 Igneous Rocks Igneous Rocks - cooled molten material form the inside the Earth(magma) or out of a volcano (lava) - the most common rock on Earth

7 Igneous Rocks B. The Earth’s crust generates great temps (1400  ), pressures, and radioactive thermal energy C. Rocks and Minerals melt to form magma, minerals have different densities and melting pts

8 Igneous Rocks

9 Classification of Igneous Rocks (1) Intrusive Igneous Rocks - those rocks that were formed from cooling magma below the Earth’s surface Cool very slowly Have large crystals called mineral grains Extrusive Igneous Rocks - Rocks that formed from cooling lava on the surface of the Earth -Cool very quickly - Have very fine grained texture

10 IGNEOUS ROCKS – cooled magma or lava Intrusive igneous rocks have large mineral grains!!!!! Extrusive igneous rocks have virtually no mineral grains.

11 Classification of Igneous Rocks (2) 1. Basaltic – dense, heavy, dark colored rock, rich in magnesium and iron, most common 2. Granitic – light color, less dense, rich in silicon and oxygen 3. Andesitic – mineral compositions in between the two, common among Pacific Volcanoes


13 Igneous Features

14 (Plutonic) Intrusive Igneous Features Magma Chamber is a large underground pool of molten rock found beneath the surface of the Earth.

15 Intrusive Igneous Features Sill is an intrusion of magma that solidifies into a horizontal layer of igneous rock

16 Intrusive Igneous Features Dike is a magma that cuts across rock layers (vertical)

17 Intrusive Igneous Features Batholith is a magma chamber that cools before reaching the surface to form a volcano

18 Intrusive Igneous Features Laccolith is a small magma chamber at shallow depth (roughly lens shaped)

19 Extrusive Igneous Features Volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface 3 types: Shield Composite Cinder

20 Extrusive Igneous Features Lava Flow – different types of lava depending on the composition and temperature

21 Extrusive Igneous Features Ash and Dust Particles

22 Extrusive Igneous Features Pyroclastic Flow is a fast-moving current of extremely hot gas ( 1,830 °F) and rock which travel away from a volcano at speeds generally as great as 450 mph.

23 Sedimentary Rocks 3 Types of Sedimentary Rocks 1) Clastic – made from rock fragments 2) Chemical – evaporation or precipitation from solution 3) Organic – contains fossils

24 Classification of Sedimentary Rocks 1) Clastic Made from sediments

25 Chemical – evaporation/precipitation

26 Organic – contain fossils Coquina Fossil-rich limestone

27 Sedimentary Rocks

28 Formation of Sedimentary Rocks Weathering and erosion makes sediment!!!! GlaciersWind GravityWater

29 Sediment Sorting Clastic Sedimentary Rocks are made of rock fragments. Parent Rock – source of rock fragments

30 Sediment Sorting - As erosional forces lose energy, sediment is deposited largest first-smallest last

31 Sediment Sorting Largest to Smallest Boulder Cobble Gravel Pebble Sand Silt Clay

32 Conglomerate Pebbles  Conglomerate

33 Sandstone Sand  Sandstone

34 Siltstone Silt  Siltstone

35 Shale Clay  Shale

36 Sediment Sorting

37 Organic Sedimentary Rock Coal – formed from the Remains of plants at the Bottom of a body of water Limestone – formed from the mixed skeletal remains of marine organisms

38 Chemical Sedimentary Rock Gypsum – easily dissolves in water… gypsum rock forms when the water evaporates and crystallizes Halite – (salt) – easily dissolves in water…halite forms when salt water evaporates and crystallizes

39 Metamorphic Rocks

40 Metamorphic Rocks - rocks that have changed due to increases in temperature and pressure (the minerals inside them change shape and alignment) - igneous, sedimentary, metamorphic rocks can metamorph B. Ex. Basalt  Schist  Gneiss Shale  Slate  Phyllite  Gneiss Granite  Gneiss

41 Metamorphic Rocks Occurs in 2 general ways: 1) Contact Metamorphism 2) Regional Metamorphism

42 Contact Metamorphism As magma pushes through rock layers beneath the Earth…nearby rock change slightly in composition and structure

43 Regional Metamorphism As the Earth’s plates move, the same extreme pressures that build mountains also cause rocks to deform and change in composition

44 WHAT HAPPENS? Heat - (2 sources- magma and depth) Minerals within the rock melt and re-crystalize thus changing the composition of the rock

45 WHAT HAPPENS? Pressure – causes space between minerals to close – compacted often causing minerals to recrystalize

46 2 classifications Foliated – banded (layers) of minerals at 90 degree angles to the pressure that caused the metamorphism Non-Foliated – no bands or layers (usually composed of only one type of mineral)

47 Metamorphic Rocks – HEAT AND PRESSURE FOLIATED = bands of mineral grainsNON-FOLIATED = no bands of mineral grains

48 Rock Classification IgneousMetamorphicSedimentary IntrusiveFoliatedClastic ExtrusiveNon-FoliatedChemical Organic Basaltic (Mafic) Andesitic Granitic (Felsic)


50 FOSSILS NJCCCS: 5.4B History of the Earth B.1, 2, 3

51 Fossils Fossil - any naturally preserved evidence of past life

52 Understanding Decomposition When an organism dies specialist organisms called decomposers and detritivores begin consuming its remains. Decomposers are usually bacteria and fungi (think sour milk and moldy bread) Detritivores are animals like vultures, hyenas, insect larvae, and a host of others (think maggots in a garbage can) Most often only the hard tissue of the organism is left behind… bones and teeth, shells, exoskeletons, etc. See Video clip – Blue Planet

53 Fossils Are Rare Fossils only form under very special environmental conditions!!!!!!! Usually found in sedimentary rocks…why? Exceptions: Volcanic ash

54 3 ways in which fossils form 1) Mineral Replacement 2) Mostly Unchanged 3) Trace

55 Mineral Replacement Underground water removes original material 1 atom at a time and replaces it with minerals. An exact copy is created out of the minerals calcite CaCO 3 or silica SiO 2. *Most Common way in which fossils form 3 basic types Petrification, Molds, Casts

56 1) Petrification the organism gets totally replaced with minerals

57 2) Molds dead creature is covered with sediments and decays away. The remaining cavity in the shape of the original creature is the fossil = impression

58 3) Cast Minerals from ground water seep into the mold, precipitate out of solution, and a stone shape is the fossil

59 Mostly Unchanged Actual original parts of an organism are left behind by several methods. 1) Simple Burial 2) Frozen 3) Amber 4) Mummification 5) Acidic Peat Bogs 6) Tar SPECIAL ENVIRONMENTAL CONDITIONS EXIST THAT PREVENT DECOMPOSITION!!!!

60 1) Simple Burial bones and teeth most often remain…share similar properties to minerals (calcium carbonate)

61 2) Frozen soft parts of mammoths have been found in frozen arctic tundra Why do we put food in a freezer? Slows down decomposition!!

62 3) Amber resin or ancient tree sap captured creatures (insects, frogs, etc.)

63 4) Mummification creatures desiccate (dry out) and soft parts remain – salt and or lye prevent decomposition

64 5) Acidic Peat Bogs creatures have been preserved in some wetlands that have environmental conditions that prevent decomposition (lack of oxygen, extreme pH)

65 6) Tar ancient oil seeping from underground trapped creatures. La Brea Tar Pits in California hold bones of mammoths, sabretooth tigers, camels, and more. Tar prevented decomposition.

66 Trace Fossil Evidence Evidence of past life NOT including plant or animal remains

67 1) Footprints 2) Burrows 3) Borings (holes) 4) Coprolites (fossil dung)

68 Fossil Lab - BE CAREFUL Some things look like fossils but really aren’t…called rock features. Ripple Marks Geodes Cross Bedding

69 Common fossils in your lab Coprolites Belemite (dung) (Squid) Trilobite Stromatolite (colony of bacteria) (arthropod) Ammonite (cuddlefish)

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