Rocks: Materials of the Solid Earth

Transcription

1 Chapter 3 Lecture Earth Science Fourteenth Edition Rocks: Materials of the Solid Earth Jennifer Mangan James Madison University

2 What is the rock cycle and why is it important?

3 The activity Deadline: 22 nd November 2014!"#$%&'()*+$%),-$*.$"#/0$-*12#3*-$.45%3)6#$*"#)4$/#%43)35$*%-7-$)3$%$/.5)&%/$8%+9$ %32$-"%4#$*"#,$/%*#4$8)*"$0##4-$ $$! "#$%&$'(&)*$+&',#-).('/01&2'3'(&)*$+&(4' '! 5--6'%&'&2$' ,'81+6' '! N+?$'(&)*$+&('2%B$')+*$#(&--*'&2$'->O$?PB$('-7'&2$1#'0-#6'&2$='0188'>$' %>8$'&-'-#,%+1Q$'%+*'#$?-#*'&2$1#'1+B$(P,%P-+('%+*'(2%#$'&2$1#'?-+?8)(1-+(' )+*$#'(&)*='%+*'1+'-#*$#'&-'.#$.%#$'1&('.#$($+&%P-+'01&2'S#$Q1'

4 The activity - The publication of the resulting products and projects can be carried through the platform of Prezi - The teacher has a prominent role in the evaluation of student work

5 Rocks materials of the solid Earth Why study rocks? We have already learned that some rocks and minerals have great economic value In additions, all Earth processes depend in some way on the properties of these basic Earth materials. Events such as volcanic eruptions, mountain building, weathering, erosion and earthquakes involve rocks and minerals.

6 Rocks materials of the solid Earth Some mountains are volcanic in origin forming where rising magma breaks through the Earth's surface. Volcanic mountains tend to have sporadic distributions within a mountain range (Mount St. Helens, Rainier, and Baker) or can occur alone because of a localized hot spot (Hawaiian Islands). Most mountains were created from tectonic forces that elevate, fold, and fault rock materials. Tectonic mountains can occur as a single range (the Urals) or as a belt of several mountain ranges (North American Cordillera).

7 Rocks materials of the solid Earth

8 Rocks materials of the solid Earth We classify rocks into three groups based on the processes that created them - Igneous - Sedimentary - Metamorphic

9 The Rock Cycle Shows the interrelationships among the three rock types Molten rock (magma) forms by melting of Earth s crust and upper mantle The magma often rises towards the surface because it is less dense than the surrounding rocks. Sometimes magma reaches Earth s surface where it erupts as lava!"#$"'/7#-@'t#$$6'uvwux'y@1z&)#$y4'1('%'@1z&)#$'-7'@-8&$+'-#'($@1!@-8&$+'#-?6['b-8%p8$(' %+*'(-81*'&2%&'1('7-)+*'>$+$%&2'&2$'()#7%?$'-7'&2$'\%#&2'

10 The Rock Cycle

11 Igneous Rocks Form as magma cools and crystallizes Rocks formed inside Earth are called plutonic or intrusive rocks Rocks formed on the surface Formed from lava (a material similar to magma, but without gas Called volcanic or extrusive rocks

12 HOW DO ROCKS BREAK DOWN? ]7'1,+$-)('#-?6('%#$'$Z.-($*'%&' &2$'()#7%?$['&2$=')+*$#,-' 0$%&2$#1+,<' ' ^2$'*%18='1+_)$+?$('-7'&2$' %&'&()*+,-)*'%+*'%*./!0/'*' #-?6(<' ' *-0+(8-.$'>=',#%B1&='%+*'&2$+'.1?6$*').'%+*'),-('0/,)*%'>=' -+$'

13 Weathering and Erosion '12"342567#81('&2$'>#$%6).'-7'#-?6('%&'&2$'\%#&2`('()#7%?$'*)$'&-' NZ=,$+' a%&$#' 8 *59:697'1('&21('#$@-B%8'%+*'&#%+(.-#&%P-+'-7'$%#&2'@%&$#1%8('>=' +%&)#%8'%,$+&(<''^2$($'%,$+&('-7'$#-(1-+'1+?8)*$:' 01+*',8%?1$#(' #1B$#(' #%1+' 0%B$('?)##$+&('

14 Igneous Rocks

15 MECHANICAL 59;C8D52"C:8958:?<63:867398:$"<<258?62;2:8EB283982F?9:B "3$9:?4252<'''

16 ICE WEDGING @-#$'(.%?$<'

17 ICE WEDGING a2$+'0%&$#'7%88('1+&-'&2$'?#%?6('-7'#-?6('%+*'7#$$q$([' &2$'7-#?$'-7'&2$'.#$(()#$' $Z$#&$*'-+'&2$'#-?6' ()##-)+*1+,'1&'1('$+-),2'&-' 0$*,$'&2$'0%88('-7'&2$'?#%?6' 7%#&2$#'%.%#&['&2)(' $Z.%+*1+,'%+*'*$$.$+1+,' &2$'?#%?6<' ]?$'0$*,1+,'1('02%&'?%)($('.-&'2-8$('1+'?1&=' (&#$$&(<'

18 WETTING AND DRYING a$d+,'%+*'j#=1+,'1(' $e$?pb$'%&'>#$%61+,').' 0$&'1&'(0$88(').['%+*'02$+' 1&'*#1$('1&'(2#1+6('%,%1+<''R-' 02$+'#-?6('&2%&'?-+&%1+'?8%='#$.$%&$*8=',$&'0$&' %+*'&2$+'*#='&2$='%#$' #$.$%&$*8='(0$881+,'%+*' (2#1+61+,'021?2'?%)($(' %.%#&<'

19 CHEMICAL WEATHERING &2%&'&2$#$'1('%+'%?&)%8'.L*!&.-M8.L-(+*'1+'&2$''.#-.$#P$('-7' &2$'#-?6'&2%&',$&('0$%&2$#$*<'''

20 OXIDATION NZ1*1Q$*'.=#1&$'?)>$('

21 ACIDS 0%&$#['021?2'?#$%&$('?%#>-+1?'%?1*['&2$'%?1*'1+'(-*%<'

22 Igneous Rocks Crystallization of magma Ions are arranged into orderly patterns Crystal size is determined by the rate of cooling Slow rate forms large crystals Fast rate forms microscopic crystals Very fast rate forms glass

23 Igneous Rocks Classification is based on the rock s texture and mineral constituents Texture Size and arrangement of crystals

24 Igneous Rocks Types of igneous textures Fine-grained fast rate of cooling Coarse-grained slow rate of cooling Porphyritic (two crystal sizes) two rates of cooling Glassy very fast rate of cooling Vesicular contains hole left by gas bubbles Pyroclastic fragmented; produced by consolidation of volcanic fragments

25 Fine-Grained Igneous Texture

26 Coarse-Grained Igneous Texture

27 Porphyritic Igneous Texture

28 Glassy Igneous Texture

29 Vesicular Igneous Texture

30 Pyroclastic Igneous Texture

31 Igneous Rocks Classification is based on the rock s texture and mineral constituents Mineral composition Explained by Bowen s reaction series which shows the order of mineral crystallization Influenced by crystal settling in the magma

32 Bowen s Reaction Series

33 Classification of Igneous Rocks

34 Sedimentary Rocks Form from sediment (weathered products) About 75 percent of all rock outcrops on the continents Used to reconstruct much of Earth s history Clues to past environments Provide information about sediment transport Rocks often contain fossils general/pastclimatesevidence.html?src=topnav

35 Sedimentary Rocks Economic importance Coal Petroleum and natural gas Sources of iron and aluminum

36 Sedimentary Rocks Classifying sedimentary rocks Two groups based on the source of the material Detrital Chemical

37 Sedimentary Rocks Detrital rocks Material is solid particles Classified by particle size Common rocks include Shale (most abundant) Sandstone Conglomerate

38 Detrital Sedimentary Rocks

39 Sedimentary Rocks Chemical sedimentary rocks Derived from material that was once in solution and precipitates to form sediment Directly precipitated as the result of physical processes, or Through life processes (biochemical origin)

40 Sedimentary Rocks Common chemical sedimentary rocks Limestone the most abundant chemical rock Microcrystalline quartz (precipitated quartz) known as chert, flint, jasper, or agate Evaporites such as rock salt or gypsum Coal compressed plant material

41 Chemical, Biochemical, and Organic Sedimentary Rocks

42 Sedimentary Rocks Sedimentary rocks are produced through lithification Loose sediments are transformed into solid rock Lithification processes Compaction Cementation by Calcite Silica Iron Oxide

43 Sedimentary Rocks Features of sedimentary rocks Strata, or beds (most characteristic) Bedding planes separate strata Fossils Traces or remains of prehistoric life Are the most important inclusions Help determine past environments Used as time indicators Used for matching rocks from different places

44 Metamorphic Rocks Changed form rocks Produced from preexisting Igneous rocks Sedimentary rocks Other metamorphic rocks

45 Metamorphic Rocks Metamorphism Takes place where preexisting rock is subjected to temperatures and pressures unlike those in which it formed Degrees of metamorphism Exhibited by rock texture and mineralogy Low-grade (e.g., shale becomes slate) High-grade (obliteration of original features)

46 Metamorphic Grade

47 Metamorphic Rocks Metamorphic settings Contact, or thermal, metamorphism Occurs near a body of magma Changes are driven by a rise in temperature Regional metamorphism Directed pressures and high temperatures during mountain building Produces the greatest volume of metamorphic rock

48 Metamorphic Rocks Metamorphic agents Heat Pressure (stress) Confining pressure from burial Differential stress occurs during mountain building Chemically active fluids Mainly water and other volatiles Promote recrystallization by enhancing ion migration

49 Confining Pressure and Differential Stress

50 Metamorphic Rocks Metamorphic textures Foliated texture Minerals are in a parallel alignment Minerals are perpendicular to the compressional force Nonfoliated texture Contain equidimensional crystals Resembles a coarse-grained igneous rock

51 Development of Foliation due to Directed Pressure

52 Metamorphic Rocks Common metamorphic rocks Foliated rocks Slate Fine-grained Splits easily Schist Strongly foliated Platy Types based on composition (e.g., mica schist)

53 Common Metamorphic Rocks

54 Metamorphic Rocks Common metamorphic rocks Foliated rocks Gneiss Strong segregation of silicate minerals Banded texture Nonfoliated rocks Marble Parent rock is limestone Large, interlocking calcite crystals

55 Metamorphic Rocks Common metamorphic rocks Nonfoliated rocks Marble Used as a building stone Variety of colors Quartzite Parent rock quartz sandstone Quartz grains are fused

56 Resources from Rocks and Minerals Metallic mineral resources Gold, silver, copper, mercury, lead, etc. Concentrations of desirable materials are produced by Igneous processes Metamorphic processes

57 Resources from Rocks and Minerals Metallic mineral resources Most important ore deposits are generated from hydrothermal (hot-water) solutions Hot Contain metal-rich fluids Associated with cooling magma bodies

58 Resources from Rocks and Minerals Types of deposits include Vein deposits in fractures or bedding planes, and Disseminated deposits which are distributed throughout the rock

59 Metallic Resources