SCI1192 Lecture 2

1. Matter
The Blue Planet: Chapter 3

2. Outline
• Earth Materials
• Organic Matter
• Composition and Internal Structure of
the Earth
• Minerals
• Rocks
• Regolith

3. Earth Materials
• The three common states of matter we
are familiar with are solid, liquid and gas
• Materials occurring in the same state
can still differ substantially
– For example, lava and water are both
liquids; one non-aqueous, one aqueous
– Both are very important in a wide variety of
Earth processes

4. Earth Materials

5. Earth Materials
Matter can coexist in various states and phases. In (A), matter of uniform
composition (H2O) coexists in two different states (liquid and solid) and two
different phases (water and ice), separated by physical boundaries. In (B),
different phases coexist in the same state (oil and water, both liquids; different
types of beans, all solids). In (C), there is only one phase and one state, as is
always the case with gases.

6. Earth Materials
• Chemical elements are the most
fundamental substances into which
matter can be separated
– An atom is the smallest individual particle
that retains the distinctive properties of a
given chemical element
• Atoms are built of protons and neutrons in the
nucleus and electrons orbiting the nucleus

7. Earth Materials
• The number of protons in the nucleus
of an atom is called the atomic
number
• Electrons are considered mass-less
• The sum of the neutrons and the
protons in the nucleus is the atomic
mass
• Isotopes are atoms with the same
atomic number but different mass
numbers
– Some isotopes are radioactive, and can
be used in radioactive dating

8. Earth Materials
• An atom is electrically neutral because
the positive charge of the protons
balances with the negative charge of
the electrons
• An atom that has excess positive or
negative charge is called an ion
– A positive ion is a cation
– A negative ion is an anion

9. Earth Materials
• Compounds form when anions and
cations combine to form a bond
• The smallest unit that retains all the
properties of a compound is called a
molecule

10. Outline
• Earth Materials
• Organic Matter
• Composition and Internal Structure of
the Earth
• Minerals
• Rocks
• Regolith

11. Organic Matter
• Possibly the most fundamental
compositional distinction is that of
organic and inorganic matter
– Organic applies specifically to compounds
consisting of carbon atoms bonded
together by covalent bonds
– In addition organic implies that the
compound is biotic in origin

12. Organic Matter
• A common characteristic of organic
compounds is their tendency to occur in
long chain-like structures called polymers
• Important biopolymers in the Earth system
– Proteins: chains of bonded amino acids
– Nucleic acids: (e.g. DNA) built of nucleotides
– Carbohydrates: the basis for most food we
eat, a carbon-hydrogen-oxygen compound

13. Organic Matter
• Lipids are another important family of
organic molecules, which are not
polymers and include
– Fats and oils
– Phospholipids
– Waxes
– Steroids

14. Outline
• Earth Materials
• Organic Matter
• Composition and Internal Structure of
the Earth
• Minerals
• Rocks
• Regolith

15. Composition and Internal Structure
of the Earth
• Earth inherited its overall composition
from its location in the solar nebula
• Earth has internal layering that
originated early in solar system history
due to chemical differentiation of the
partially molten planet
– Layers are distinguished by composition,
rock strength, and state of matter

16. Composition and Internal
Structure of the Earth
• There are three
major compositional
layers in the Earth
– Core: metallic iron
solid inner core and
liquid outer core
– Mantle: dense rocky
matter
– Crust: thin, less
dense rocky matter

17. Composition and Internal Structure
of the Earth
• The core and mantle have nearly
constant thicknesses, but the crust
varies in place to place by a factor of 9
• The average oceanic crust is 8 km thick
• The average continental crust is 45 km
thick, but ranges from 30-70 km
• The two crusts also differ fundamentally
in composition

18. Composition and Internal Structure
of the Earth
• Scientific reasoning, indirect sampling,
and indirect measurement provide
information about the core and mantle
that otherwise is inaccessible
• In addition to compositional layering,
the Earth contains layers with
differences in rock strength

19. Composition and Internal Structure
of the Earth
• Mesosphere: “middle sphere” within the
mantle
• Asthenosphere: “weak sphere” in the
uppermost mantle
• Lithosphere: “rocky sphere” the
outermost 100 km

20. Composition and Internal Structure
of the Earth
• Of the 92 naturally occurring chemical
elements, only 12 occur in Earth’s crust
• The crust is dominated by two elements
– Oxygen
– Silicon
• With the other ten elements, these are
responsible for the composition of all
common Earth materials

21. Composition and Internal
Structure of the Earth

22. Outline
• Earth materials
• Organic matter
• Composition and internal structure of
the Earth
• Minerals
• Rocks
• Regolith

23. Minerals
• Minerals are the building blocks of the
geosphere, they are or have:
– Naturally formed
– Inorganic
– Solid
– Specific chemical composition
– Characteristic crystal structure

24. Minerals
• The two characteristics that best allow
the study of minerals are
1. Crystal structure: the way the atoms of
the elements are packed together
2. Composition: the major chemical
elements that are present and their
proportions

25. Minerals
• Because of their abundance, oxygen
and silicon form the basis for the most
common rock-forming minerals, and the
most common mineral group: silicates
• Other mineral groups include: oxides,
sulfides, carbonates, sulfates, and
phosphates

26. Minerals
• Silicates
– Built of the silicate
anion (tetrahedron)
– The anion joins
together by sharing
their oxygen atoms to
form chains, sheets
and three-dimensional
networks

27. Minerals

28. Minerals
• Silicates are by far the most abundant
minerals in the continental crust, and
feldspars are the predominant variety
– Feldspars: 60% of minerals in Earth’s crust
– Quartz: 15% of minerals in Earth’s crust
– All silicates: 95% of minerals in the crust
• This limits non-silicates to only 5% of
the Earth’s crust!

29. Minerals
• Minerals are identified by their distinct
properties that result from their
composition and crystal structure
– Crystal form and growth habit
– Cleavage
– Luster
– Hardness and specific gravity
– Color

30. Minerals
• Crystal form and growth habit
– In 1669, Nicolaus Steno discovered that
the angle between mineral crystal faces is
constant and gives each a distinctive
crystal form
– He speculated this was due to ordered
particles, but proof by use of x-rays would
not arrive until 1912
– Crystals only form when a mineral can
grow freely in open space

31. Minerals

32. Minerals
• Cleavage
– A mineral’s tendency to break in preferred
directions along weak planar surfaces
• Luster, Color and Streak
– The quality and intensity of light reflected from
a mineral surface is luster
– Color is often not a reliable means of
identification, as it can be determined by
chemical impurities in the composition
– Color in opaque minerals can be a property of
grain size, this can be resolved using the
mineral’s streak

33. Minerals

34. Minerals
• Hardness
– This term refers to the relative resistance
of a mineral to being scratched
– This is governed by the crystal structure
and the strength of chemical bonds
– Hardness is classified using Moh’s relative
hardness scale, which has 10 hardnesses
that are not at equal intervals

35. Minerals

36. Minerals
• Density and specific gravity
– Specific gravity is easier to measure, and
therefore more commonly used
– It is the ratio of the weight of the substance
to the weight of an equal volume of pure
water
– The densities of some minerals are
distinctive; such as gold and galena

37. Outline
• Earth materials
• Organic matter
• Composition and internal structure of
the Earth
• Minerals
• Rocks
• Regolith

38. Rocks
• A rock is any naturally formed,
nonliving, coherent aggregate mass of
solid matter that constitutes part of a
planet, asteroid, moon, or other
planetary object
• Minerals are the most common and
abundant building blocks of rocks

39. Rocks
• There are three families of rocks
– Igneous: formed from the cooling and
consolidation of magma or lava
– Sedimentary: formed from either chemical
precipitation of material or deposition of
particles transported in suspension
– Metamorphic: formed from changing a rock
as a result of high temperatures, high
pressures, or both

40. Rocks
• Earth’s crust is mainly igneous and
metamorphic rock, however, most of
the rock we see at surface is
sedimentary

41. Rocks
• The two main features that best classify
rocks are
– Texture: the overall appearance of a rock,
resulting from the size, shape, and
arrangement of its mineral grains
– Mineral assemblage: the kinds and relative
amounts of minerals present

42. Rocks

43. Rocks

44. Rocks

45. Outline
• Earth materials
• Organic matter
• Composition and internal structure of
the Earth
• Minerals
• Rocks
• Regolith

46. Regolith
• Rock exposed at Earth’s surface is
susceptible to alteration by the action of
water, wind, and other agents that
physically and chemically break it apart
and alter it
• This broken-up, disintegrated rock
matter is called the regolith

47. Regolith
• Literally “blanket rock,” the regolith forms a
layer draped over most of Earth’s surface
• Three categories describe most of the
various materials of the regolith
– Saprolite: rock that is weathered in situ
– Sediment: loose rock and mineral particles
• Clastic sediment (broken particles)
• Chemical sediment (dissolved material)
– Soil: contains organic matter mixed with
minerals, can support rooted plants

48. Regolith

49. Space and Time
The Blue Planet: Chapter 4

50. Outline
• The Sun
• The Solar System
• Other Suns and Planetary Systems
• Time and Change

51. The Sun
• Each visible point of light in the night
sky, except nearby planets, is actually a
sun or collection of suns
• Or rather, our Sun is an ordinary star
• The is dominated by hydrogen and
helium at 98% of its mass
• Of course, the Sun provides the light
and energy for life to exist on Earth

52. The Sun

53. The Sun

54. Outline
• The Sun
• The Solar System
• Other Suns and Planetary Systems
• Time and Change

55. The Solar System
• Beyond the Sun, there are 8 planets in the solar
system, at least 5 dwarf planets and vast
numbers of asteroids, comets, meteoroids, and
moons
• The innermost planets are small, rocky, metallic,
and dense: terrestrial planets
– Mercury, Venus, Earth and Mars
• The outer planets are much larger, less dense
and gaseous: Jovian planets (gas giants)
– Jupiter, Saturn, Uranus and Neptune

56. The Solar System
• The early model of our solar system was
geocentric, meaning that people thought all
objects revolved around the Earth
• Today we know it is heliocentric, meaning that all
objects revolve around the Sun
• Any hypothesis for the origin of the solar system
must account for as many of its features as
possible:
– All solar system objects revolve in the same direction,
around the sun, moons around their respective
planets, and all on the same plane, consistently

57. The Solar System

58. The Solar System
• The origin of the Sun was probably
similar to the origins of billions of other
stars in the universe, so the prevailing
model for the origin of the solar system
is the nebular hypothesis
• This proposes that a huge swirling
cloud of cosmic gas and dust (a nebula)
formed the sun and planets

59. The Solar System

60. The Solar System
• Gravity pulled the slowly swirling cloud
of dust and gas inward, as this
happened the gar became hotter and
denser
• Eventually temperature and pressure
was high enough that nuclear fusion
started and a star was born: the Sun
• Surrounding the new Sun was a
flattened, rotating disc of gas and dust

61. The Solar System
• By the time the Sun started burning, the cooler
outer portions of the solar nebula had become
so compressed that solid particles and liquid
droplets began to condense from the gas
• These condensates, through accretion,
became the building blocks of the planets,
moons, and other objects in the solar system
• Distance from the Sun and condensation
temperatures explain the distinct materials of
the terrestrial and Jovian planets

62. The Solar System
• Space missions continue to provide
evidence indicating that all objects in
the solar system formed at the same
time from a single solar nebula
• Beyond the end of the nebular
hypothesis story, five key factors played
determining roles in the subsequent
evolution of the terrestrial planets

63. The Solar System
• Melting, impacts, and differentiation
– Colliding bodies convert kinetic energy into
heat energy
– As planetary accretion climaxed about 4.56
billion years ago, bigger collisions mean
more kinetic energy and more heat
– Terrestrial planets began to melt, at least
partially, and dense metallic liquids sank
while lighter materials floated
– Planetary differentiation by chemical
segregation

64. The Solar System

65. The Solar System
• Volcanism
– After partial melting, the interior of the
planets still remained hot because of
radioactive elements
– All planets are slowly cooling, larger
planets slower than smaller planets
– Volcanism is an indicator of high internal
temperature

66. The Solar System

67. The Solar System
• Planetary mass
– Determines the orbit of a planet, and how
many moons it captures
– Determines whether the planet has
sufficient gravitational pull to hold onto its
atmosphere

68. The Solar System

69. The Solar System
• Distance from the Sun
– Determines if water can exist as a liquid
• Biosphere
– Presence or absence of a biosphere plays
an essential role in the development of the
biogeochemical cycles that control the
composition of Earth’s atmosphere

70. The Solar System

71. The Solar System
• We do not know if any other terrestrial
planets have molten or partially molten
cores, which has provided Earth with a
strong magnetic field
• All terrestrial planets have experienced
volcanic activity, indicating an internal
heat source, and have been through
intense collisions
• Apparently unique to Earth is tectonic
activity

72. The Solar System
• The outer planets are shrouded by thick
atmospheres that have not escaped the
planets’ enormous gravitational pull
• Their bulk compositions are therefore
about the same as the nebula from which
they formed: Jupiter’s composition is
remarkably similar to that of the Sun
• Huge storm systems are common in the
gas giants’ atmospheres, and all probably
have rocky cores

73. The Solar System

74. The Solar System
• Moons
– The 19 largest moons are roughly spherical
in shape, the smaller ones can be extremely
irregular
– Some formed by coalescence from the same
mass as the solar nebula, others by
gravitational capture, and others by collision
– Earth’s moon is 1/4 the size of Earth, making
it the largest natural satellite in comparison
with its parent planet, it likely formed from a
catastrophic collision

75. The Solar System

76. The Solar System
• Asteroids and Meteorites
– Subplanetary objects orbiting the sun
– Commonly rocky and/or metallic
• Pluto and the Dwarf Planets
– Minor planets or small bodies that are
orbiting the sun, massive enough to be
spherical, but not massive enough to have
cleared its orbital path
– In addition to Pluto, are Eris, Haumea,
Makemake, and Ceres

77. The Solar System

78. The Solar System
• Comets, the Kuiper Belt, and the Oort Cloud
– The dwarf planets belong to a group that
includes thousands of other objects outside of
Neptune’s orbit called the Kuiper Belt
– Similar to the Asteroid belt in appearance, but
consists mainly of icey rather than rocky bodies,
akin to comets
– The Oort Cloud is further out still, and also
appears to be a store of cometary material

79. The Solar System

80. Outline
• The Sun
• The Solar System
• Other Suns and Planetary Systems
• Time and Change

81. Other Suns and Planetary Systems
• Stars are classified by color and
brightness
– Color is an indication of temperature, blue
light comes from short wavelengths and is
hot, while red light comes from long
wavelengths and is cool
– Each color designates the star’s spectral
class, from 9 (hottest) to 0 (coolest)

82. Other Suns and Planetary Systems

83. Other Suns and Planetary Systems
• A star’s brightness is a function of both the
star’s luminosity (energy emitted) and its
distance from the Earth
– This requires a normalization of star
distances, which is difficult to measure, but
can be done to 300 light-years
• Once temperature and luminosity are
known, they can be compared with values
on the Hertzsprung-Russell diagram
– White dwarfs, main sequence and red giants

84. Other Suns and Planetary
Systems

85. Other Suns and Planetary Systems
• The H-R diagram can be used to
explain the evolution of a star
– The smaller the star, the longer it can live
• For the lifetime of most stars, a balance
is reached between gravitational and
radiation forces, where it maintains the
stable luminosity and temperature of a
main sequence star

86. Other Suns and Planetary Systems
• A star the size of our Sun will fuel
nuclear fusion for about 10 billion years
• When the hydrogen fuel is used up,
nuclear fusion ceases, gravity takes
control, and the helium-rich core
contracts
• As the core collapses, it heats up, and a
shell of hydrogen in the inner radiative
layer begins shell fusion, the star
expands, and becomes a red giant

87. Other Suns and Planetary
Systems

88. Other Suns and Planetary Systems
• The core continues to contract,
eventually becoming hot enough for
helium fusion to form carbon, the shell
slowly diminishes in size becoming a
white dwarf
• Eventually it loses its luminosity and
becomes a dead star known as a black
dwarf

89. Other Suns and Planetary Systems
• Astronomers believe that 5-10% of the
200-400 billion stars in the Milky Way
have characteristics similar to those of
our Sun, and it is likely that they have
planetary systems like our own
• These planets are called exoplanets,
and as of June 2009, 353 exoplanets
had been found

90. Outline
• The Sun
• The Solar System
• Other Suns and Planetary Systems
• Time and Change

91. Time and Change
• Scientists estimate the age of the
universe by looking at the rate at which
objects are moving apart from each
other
• The hypothesis is that everything
originated at one location in an explosion
called the Big Bang
• The universe is 2 to 3 times as old as
the Sun and the solar system

92. Time and Change
• To deal with the ages of materials within
the Earth system and elsewhere in the
universe, scientists use two concepts of
time and age
– Relative age: refers to the order in which a
sequence of past events occurred
– Numerical age: is the actual time, in years,
when a specific event happened,
calculated using radioactive decay

93. Time and Change

94. Time and Change
• Using these tools and worldwide
comparison and correlation of rock
units, geologists have assembled a
geologic column that summarizes in
chronological order the succession of
known rock units
– Major divisions include the Hadean,
Archean, Proterozoic, Paleozoic, Mesozoic
and Cenozoic Eons

95. Time and Change

96. Time and Change
• In the 17th and 18th centuries, people
hypothesized that all of Earth’s features
were formed by a few great catastrophic
events - this idea is catastrophism
• In the late 18th century, this idea was
tested with geological evidence
• James Hutton, with the use of the
scientific method, proposed a counter
theory called the principle of

97. Time and Change
• Hutton observed the slow, steady effects of
erosion
• Determined that mountains must slowly
weather away, that new rocks form from
the debris of erosion, and be thrust back up
into mountains
• Couldn’t explain what caused this to
happen, but reasoned that everything
moves slowly in repetitive continuous
cycles

98. Time and Change
• The principle of uniformitarianism, which
essentially states that “the present is the
key to the past,” indicates that the Earth
is incredibly old
• This concept is important to all branches
of science, but we also know that some
events are so large and damaging that
they can cause catastrophic change

99. Time and Change