grade 7 lesson about the solid part of the Earth - Lithosphere

1. Layers of the Earth

2. 4. The 6-35 km (4-21 miles)
thick lithosphere. Earth's
crust.
3. The 2900 km (1.800 miles)
thick Mantle layer formed
from rapidly flowing magma.
2. The 2000 km (1,250 miles)
thick outer core containing
such molten heavy metals as
nickel and iron.
1. The 1370 km (851 miles) thick inner core, which is in a
crystalline state because of the influence of heat and
high pressure.

3. Lithosphere
The solid part of the earth.
It consists of three main
layers: crust, mantle and
core.

4. The Crust
Is the outermost layer of the earth.
Has a depth of about 32 to 40 km.
The thinnest layer.
The uppermost layer is known as the SIAL.
It is composed mainly of silicon and aluminum
The bottom layer of the crust is called SIMA
It is made mostly of silicon and magnesium.

5. Crust are further divided into two major parts:
Continental crust
It is about 32 kilometers thick, made mainly
of granite rocks.
The elevated portion of the crust.
Oceanic Crust
The ocean bed, it is
about seven kilometers
thick and made mainly
of basalt.

6. The Mantle
Located just below the crust.
It is denser than crust, about 2,900
km thick.
It is composed mainly of very
hot, solid rocks that flow.
The region between the crust and the
mantle is called MOHOROVICIC
DISCONTINUITY OR MOHO.
Scientists have been able to confirm
the differences in density between
rocks of the crust and those of the
mantle by studying the Moho.

7. The Core It is about 4,960 km
deep.
It is divided into:
Outer core
It is about 2,270 km
thick
Composed mainly of
nickel and iron melted
by intense heat.
The temperature ranges
from 4,000 C to 5,000 C
Inner Core
It is composed mainly of solid iron and nickel.
The temperature is around 5,000 C to 6,000 C.
The pressure is exceedingly high.

11. Materials of the
Earth

14. Igneous Rocks

15. (1) Basalt:
are dark colored, fine-grained extrusive rocks.
The mineral grains are so fine that they are
impossible to distinguish with the naked eye
or even a magnifying glass.
They are the most widespread of all the
igneous rocks.
Most basalts are volcanic in origin and were
formed by the rapid cooling and hardening of
the lava flows.
Some basalts are intrusive having cooled
inside the Earth's interior.

17. (2) Gabbro:
is a dark-colored, coarse-grained intrusive
igneous rock.
Gabbro is very similar to
basalt in its mineral make
up.

18. (3) Pumice:
is a very light colored, frothy volcanic rock.
Pumice is formed from lava that is full of gas.
The lava is ejected and shot through the air
during an eruption.
As the lave hurtles through the air it cools and
the gases escape leaving the rock full of holes.
Pumice is so light that is actually floats on water.
Huge pumice blocks have been seen floating on
the ocean after large eruptions.
Pumice is ground up and used today in soaps, abrasive
cleansers, and also in polishes.

19. (3) Pumice: is a very light colored, frothy volcanic rock. Pumice is
formed from lava that is full of gas. The lava is ejected and shot
through the air during an eruption. As the lave hurtles through the
air it cools and the gases escape leaving the rock full of holes.
Pumice is so light that is actually floats on water. Huge pumice
blocks have been seen floating on the ocean after large eruptions.
Some lava blocks are large enough to carry small animals. Pumice
is ground up and used today in soaps, abrasive cleansers, and also
in polishes.

20. (4) Rhyolite: is very closely related to granite. The
differences is rhyolite has much finer crystals. These
crystals are so mall that they can not be seen by the
naked eye. Rhyolite is an extrusive igneous rock having
cooled much more rapidly than granite, giving it a
glassy appearance. The minerals that make up rhyolite
are quartz, feldspar, mice, and hornblende.

21. (5) Granite: is an igneous rock that is composed of four minerals. These minerals
are quartz, feldspar, mica, and usually hornblende. Granite forms as magma
cools far under the Earth's surface. Because it hardens deep underground, it
cools very slowly. This allows crystals of the four minerals to grow large enough
to be easily by the naked eye. Granite is an excellent material for building
bridges and buildings because it can withstand thousands of pounds of pressure.
It is also used for monuments because it weathers slowly. Engraving in granite
can be read for hundreds of years, making the rock more valuable. Granite is
quarried in many places in the World including the United States. The state of
Hew Hampshire has the nickname "Granite State" because of the amount of
granite in the mountains of that beautiful state. The Canadian Shield of North
American contains huge outcroppings (surface rocks) of granite.

22. (6) Obsidian: is a very shiny natural volcanic glass. When obsidian
breaks its fractures with a distinct conchoidal fracture. Obsidian is
produced when lava cools very quickly. The lave cools so quickly
that no crystals can form. When people make glass they melt silica
rocks like sand and quartz then cool it rapidly by placing it in
water. Obsidian in produced in nature in a similar way. Obsidian is
usually black or a very dark green, but it can also be found in an
almost clear form. Ancient people throughout the World have
used obsidian for arrowheads, knives, spearheads, and cutting
tools of all kinds. Today obsidian is used as a scalpel by doctors in
very sensitive eye operations.

23. Metamorphic Rock:
(1) White Marble: is a metamorphosed limestone or dolomite. both limestone
and dolomite have a large concentration of calcium carbonate (CaCO3). Marble
has many different sizes of crystals. Marble has many color variances due to
the impurities present at formation. Some of the different colors of marble are
white, red, black, mottled and banded, gray, pink, and green. Marble is much
harder than its parent rock. This allows it to take a polish which makes it a good
material for use as a building material, making sink tops, bathtubs, and a
carving stone for artists. Today, headstones are made from marble and granite
because both of these rocks weather very slowly and carve well with sharp
edges. Marble is quarried in Vermont, Tennessee, Missouri, Georgia, and
Alabama.

24. (2) Slate: is a fine-grained metamorphic rock with perfect cleavage that allows it
to split into thin sheets. Slate usually has a light to dark brown streak. Slate is
produced by low grade metamorphism, which is caused by relatively low
temperatures and pressures. Slate has been used by man in a variety of ways
over the years. One use for slate was in the making of headstones and grave
markers. Slate is not very hard and can be engraved easily. The problem with the
slate though is its perfect cleavage. The slate headstones would crack and split
along these cleavage planes. This in not a desirable attribute for a headstone.
Slate was also used for chalk boards. The black color was good as a background
and the rock cleaned easily with water. Today it is not very advantageous to use
this rock because of its weight and the splitting and cracking over time.

25. (3) Schist: is a medium grade metamorphic rock. This means that
is has been subjected to more heat and pressure than
slate, which is a low grade metamorphic rock. The individual
grains of minerals can be seen by the naked eye. Many of the
original minerals have been altered into flakes. Because it has
been squeezed harder than slate it is often found folded and
crumpled. Schists are usually named by the main mineral from
which they are formed. Bitotite mica schist, hornblende
schist, garnet mica schist, and talc schist are some examples of
this.

26. (4)Gneiss: is a high grade metamorphic rock. This means that
gneiss has been subjected to more heat and pressure than schist.
Gneiss is coarser than schist and has distinct banding. This
banding has alternating layers that are composed of different
minerals. The minerals that compose gneiss are the same as
granite. Feldspar is the most important mineral that makes up
gneiss along with mica and quartz. Gneiss can be formed from a
sedimentary rock such as sandstone or shale, or it can be formed
from the metamorphism of the igneous rock granite. Gneiss can
be used by man as paving and building stone.

27. (5) Quartzite: is composed of sandstone that has been
metamorphosed. Quartzite is much harder than the
parent rock, sandstone. It forms from sandstone that
has come into contact with deeply buried magmas.
Quartzite looks familiar to its parent rock. The best way
to tell quartzite from sandstone is to break the rocks.
Sandstone will shatter into many individual grains of
sand while quartzite will break across the grains.

28. (6) Anthracite Coal: is organic sedimentary rocks formed from the build up and decay of
plant and animal material. This usually forms in swamp regions in which there is an
abundant supply of growing vegetation and low amounts of oxygen. The vegetation builds
so quickly that new layers of vegetation bury the dead and decaying material very quickly.
The bacteria that decay the vegetation need oxygen to survive. Because these decaying
layers are buried so fast the bacteria use up what oxygen there is available and can not
finish the decomposition of the vegetation. The overlaying layers become so heavy that
they squeeze out the water and other compounds that aid in decay. This compressed
vegetation forms coal. The longer and deeper that coal is buried makes it of higher
quality. Peat is the first stage of coal formation. Lignite is the next grade of coal followed
by bituminous and the highest grade, anthracite. Anthracite is actually a metamorphic
rock. It forms during mountain building when compaction and friction are extremely high.
This form of coal burns very hot and almost smokeless. It is used in the production of high
grade steel.

29. Sedimentary Rocks:
(1) Limestone: is the most abundant of the non-clastic sedimentary rocks.
Limestone is produced from the mineral calcite (calcium carbonate) and
sediment. The main source of limestone is the limy ooze formed in the ocean.
The calcium carbonate can be precipitated from ocean water or it can be
formed from sea creatures that secrete lime such as algae and coral. Chalk is
another type of limestone that is made up of very small single-celled
organisms. Chalk is usually white or gray in color. Limestone can easily be
dissolved by acids. If you drop vinegar on limestone it will fizz. Put a limestone
rock into a plastic jar and cover it with vinegar. Cover the jar and watch the
bubbling of the calcium carbonate and also the disintegration of the rock over
a few days.

30. (2) Breccia: is formed in a very similar fashion to
conglomerate. The difference between the two rocks is
that breccia's rock fragments are very sharp and
angular. These rock fragments have not been
transported by water, wind, or glaciers long enough to
be rounded and smoothed like in the conglomerate.
The cementing agents silica, calcite (CaCO3), and iron
oxides are the same as in conglomerate.

31. (3) Conglomerate: is a clastic sedimentary rock that forms from
the cementing of rounded cobble and pebble sized rock
fragments. Conglomerate is formed by river movement or ocean
wave action. The cementing agents that fill the spaces to form the
solid rock conglomerate are silica, calcite, or iron oxides. Notice in
the photo above the rounded rock particles in the conglomerate.
These rounded particles make conglomerate different from
breccia.

32. (4) Sandstone: is a clastic sedimentary rock that forms
from the cementing together of sand sized grains
forming a solid rock. Quartz is the most abundant
mineral that forms sandstone. Calcium carbonate, silica,
or iron has been added to the water that is in contact
with the sand grains. These minerals grow crystals in
the spaces around the sand grains. As the crystals fill
the gaps the individual sand grains are now transformed
into a solid rock.

33. (5) Halite: is common table salt. It forms where brakish (salty)
lakes or sea beds dry up. This evaporation of the water causes the
salt to precipitate forming the salt crystals. Halite frequently
occurs in crystal form. It is usually colorless but can be reddish
brown because of iron oxides in the water that it forms in. Halite
has perfect cleavage and a hardness o 2.5 on the Mohs hardness
scale.

34. Story 1: "Rock"in Stories
Kate was in her career development class at
Cherokee Middle School. She was very interested
in the subject of earth science and wanted to
know more about Geology and the formation of
rocks through geochemical process, such as,
igneous, metamorphic and sedimentary.
She interviewed a scientist, Dr. Gutierrez at
Southwest Missouri State University to feed her
curiosity. They planned a journey to the
Springfield rock quarry. Kate met Dr. Gutierrez and
they traveled to the rock quarry.

35. Kate and Dr. Gutierrez had to wear helmets to enter the
rock quarry due to the blasting of slabs of stone with
dynamite. Kate was overwhelmed with all the different
kinds of rocks. She picked up a light whitish grey rock.
Dr. Gutierrez told her the rock was composed of
Calcium Carbonate, CaC03, This type of rock is formed
from sea creatures that secrete lime, such as algae and
coral. When they die their remains pile up on the ocean
floor and form this rock.
What kind of rock would this be? What stage of
the rock cycle is the rock found?
Limestone - Sedimentary

36. Dr. Gutierrez informed her that the rock
she found is the parent of another kind of
rock that is much harder. This rock is made
up of different sizes of crystals and has
many variations in color. This rock may be
red, white, pink, or grey. It is used as a
building material to make countertops and
bathtubs.
What kind of rock would this be? What
stage of the rock cycle is this rock found?
Marble - Metamorphic

37. The beginning of these rocks occurred 30
meters below the Earth's surface. There the
rock was dark colored and fined grained. This
rock is the most widespread of this stage of
rocks. This rock is volcanic in origin and formed
by rapid cooling and hardening of lava.
What kind of rock would this be? What
stage of rock cycle is this rock found?
Basalt - Igneous

38. Story 2
Whitney, a very intelligent graduate, completing her
masters in Geology decided to go on a research field class
for the summer. The instructor for this class was Dr.
Playmate, a Geologist of Southwest Missouri State
University.
They traveled to the Rocky Mountains for their geological
research. While hiking, they discovered an exposed cliff
that had been subjected to weathering.
Within this cliff they found a rock that was composed of
the minerals feldspar, mica, and quartz. This rock had a
banned appearance in its layers.
What kind of rock would this be? What stage of rock
cycle is this rock found?
Gneiss - Metamorphic

39. Whitney informed her classmates that this
rock can be formed from several other types
of rocks. One of these rocks forms from the
cementing together of small grains. Quartz is
the most abundant mineral in this kind of
rock.
What kind of rock would this be? What stage of
rock cycle is this rock found?
Sandstone - Sedimentary

40. The rock in the cliff could also be formed from a
completely different type of rock. This rock is composed
of four minerals: quartz, feldspar, mica, and
hornblende. This rock forms as magma cools far under
the Earth's surface. Because it hardens underground, it
cools slowly. This allows the crystal of the four minerals
to grow large enough to be seen by the naked eye. This
type of rock is excellent of building bridges and
monuments because it weathers slowly.
What kind of rock would this be? What stage of
rock cycle is this rock found?
Granite - Igneous

41. Story 3:
Jessica, after completing a very rough semester
at Southwest Missouri State University, decided
to take a vacation to Hawaii with her frequent
flyer miles. She decided to go to the National
Volcano Park to elevate some stress. The park
encompasses diverse environments that range
from seal level to the summit of the Earth's
most massive volcano, Mauna Loa at 13,677
feet. After a recent volcanic eruption she took a
guided tour. On this tour, she observed many
different types of volcanic rock.

42. One in particular was very light colored and light
in weight. This rock is so light that it floats on
water. It had holes all throughout the rock. This
rock is formed when lava is ejected and shot
thru the air during a volcanic eruption. As the
lava flies thru the air it cools and gases escape
leaving the rock full of holes. This rock is used
today in soap and abrasive cleaners.
What kind of rock would this be? What stage of
rock cycle is this rock found?
Pumice - Igneous

43. They traveled on and came to a beautiful flowing
stream. The guide picked up a hand full of rocks
and Jessica noticed one that appeared to have
many tiny rocks inside of it. This rock was
formed by river movement and composed of
rounded cobble and pebble sized rock
fragments.
What kind of rock would this be? What
stage of rock cycle is this rock found?
Conglomerate - Sedimentary

44. After the guided tour, Jessica to take a walk on
the beach of Hawaii. As she walked, she picked
up shells and rocks from the sand. She noticed
one of the rocks looked like it had been formed
from the cementing together of small sand sized
grains. This rock looked like sandstone, but
when broken, the grains of sand broke into
layers.
What kind of rock would this be? What
stage of rock cycle is this rock found?
Quartzite - Metamorphic

45. Rock Name Description Rock Type
Dark colored, fine grained; formed by rapid
Basalt Igneous
cooling and hardening of lava flow
Dark colored, coarse-grained; similar to basalt
Gabbro but mostly composed of the mineral Igneous
plagioclase feldspar
Light colored, frothy volcanic rock; formed
Pumice when lava is ejected and shot through the air Igneous
during an eruption; so light is can float
Closely related to granite, but has very fine
Rhyolite crystals; has a glassy appearance; made up of Igneous
quartz, feldspar, mica and hornblende
Composed of the same minerals as rhyolite;
Granite forms as magma cools far under the earth's Igneous
surface
Very shiny natural volcanic glass; produced
Obsidian when lava cools very quickly so no crystals Igneous
form; usually black or very dark green;

46. Minerals
They are naturally formed solid elements
or compounds having a crystalline
structure and possessing physical and
chemical properties.
They are considered as the building units
of the Lithosphere.

47. The element composing the Minerals
Oxygen
Oxygen in its combined form is the
most abundant element composing
minerals.
It is found chemically combined with
other elements forming OXIDES.
Very few minerals are found to be
composed of pure elements.

48. What is the relationship of Rocks and
Minerals?
Are familiar with a fruit cake?
Fruit cake is a loaf of bread with nuts, raisins
and glazed fruits.
The fruit cake
represents the
rock, the
nuts, raisins and
glazed fruits
represents the

49. Properties used in Identifying Minerals
MINERALOGY is the science that deals
with the identification and classification of
minerals.
Mineralogists subject the minerals to
various tests to determine their properties.

50. Properties used in Identifying Minerals
1. Color
This is the most obvious property of mineral.
However, not all minerals can be identified by
color for three reasons:
a) Many minerals are colorless or else they
have the same color.
b) Impurities affect the real color of the
mineral.
c) Surface color tarnishes
Example: Corundum is a colorless mineral. With traces of
Chromium, it becomes red called (ruby) and with traces of
iron and titanium it becomes blue called ( sapphire)

51. 2. Luster
This is the property of the mineral to reflect,
refract or absorb light.
Some minerals “shine’ when exposed to light
while others do not.
Some terms used to describe luster are:
BRILLIANT, DULL, PEARLY, SILKY, EA
RTHY and many more.

52. 3. Streak
The color of the fine powder of the
mineral made against a streak plate.
Some minerals have streaks similar to
their color. Others have streaks
different from their colors.
Gold is yellow, and its streak is also yellow.
Pyrite (known as fool’s gold) has a greenish-black
streak.
Hematite is black but its streak is red.

53. Identifying Minerals
by Streak
Gold(top), platinum
(middle) and
copper (bottom)
have characteristic
streak colors, best
seen on a black
streak plate.

54. 4. Crystal Form
Minerals are usually crystalline and some
minerals have enchanting crystals.
Crystal form reveals the arrangement of atoms
in a mineral.
The atoms of each mineral are arranged in a
definite geometric pattern.
Each mineral had its own definite atomic
arrangement which is helpful in identifying that
particular mineral.

56. 5) Cleavage and Fracture
This property reveal the structure of a
mineral.
Cleavage is the splitting of the mineral readily
along certain planes to produce flat and
smooth surfaces.
Uneven breaks or cracks that form uneven
surfaces are called FRACTURE.

57. 6. Specific Gravity
This is the number that tells how many times
denser the minerals is than an equal volume
of water.
In determining the specific gravity of a
mineral. Its volume and mass are first
determined. Then the density is computed
using the formula:
D=M/V

58. The resulting density is compared with the density of
water which is equal to 1 g/cm3.
For example, the density of silver is 10.6 g/cc. This is
then compared to the density of water. Thus,
Specific gravity = density of silver / density of water
= 10.6 g/cc / 1g/cc
= 10.6
Silver is 10.6 times denser than water.

59. Specific Gravity of Some Minerals
Minerals Specific Gravity
Gold 19.3
Mercury 13.6
Platinum 21.5
Silver 10.6
Copper 9.0
Zinc 7.1
Pyrite 5.2
Garnet 4.2
Diamond 3.5
Talc 2.8
Calcite 2.7
Quartz 2.6

60. 7. Hardness
This is the resistance of a mineral to being
scratched.
The test for the hardness of a mineral
involves the use of scale invented by
Friedrich Mohs.

61. The Moh’s Scale of Hardness
1. Talc 6. Orthoclase
2. Gypsum 7. Quartz
3. Calcite 8. Topaz
4. Fluorite 9. Corundum
5. Apatite 10. Diamond

63. The Forces the
Construct the
Earth’s Surface

64. Diastrophism or Crustal Warping
Pertains to all the movements of the solid
parts of the earth.
Great forces act on the crust causing it to
move.
Sometimes:
the movement is so strong and sudden that we
can feel the shaking of the ground.
the movement may be so slow that we can not
feel them, can only be detected by a
seismograph.
The great forces that cause the felt and unfelt
movements of the crust have been identified as
pushes (compression) and pulls (tension) exerted on
the crust over long period of time.

65. Direction of Forces and the
Movement they Produce
1. Upward forces
Upward forces cause the local
widespread rising or uplift of the crust.
These forces are responsible for the
emergence of small islands in the deep
seas of the pacific.
The discovery of the fossil remains of
marine organisms in the rock layers of
high areas indicates that these layers
were pushed up from under the water of
the ocean.

68. 2. Downward Forces
Downward forces cause the local or
widespread sinking or subsidence of the
crust.
These forces caused the disappearance of
small islands in the pacific in the
historic past.
The fossil remains found in the rock
layers reveal that there was at one time a
land bridge connecting Asia and North
Africa.
Such a land bridge and many more have
been submerge or pushed underwater by
great forces.

71. 3. Sideward Forces
Sideward forces cause the
horizontal motion of the crust
called thrust.
Large masses of rocks slide and
slip against each other into new
position.
Sometimes rock masses
bend, tilt, or wrinkle due to these
sideward forces.

73. Effects of Diastrophism
The movement of the crust brought
about by the interaction of the
forces described has resulted in the
formation of the different surface
features of the earth.

74. 1. Folding
Folding occurs when the crust crumples or
wrinkles due to compressions or pushes
from opposite directions.

75. As the crust is crumpled, the rock strata
become tilted.

76. The materials of the crust are dense and
rigid, but under great heat and pressure,
they soften and can be deformed.
The crest or upward curve of a fold is
called anticline.
The trough or downward curve is called
syncline.

77. The crest may form
mountains, hills or ridges and the
trough may form valley.

78. 2. Faulting
Faulting occurs when a rock masses
of the crust are pulled apart (tension)
forming cracks or fractures on the
crust.
The tensional forces go beyond the
elastic limit of the crust that it yields
to the stress by breaking.

79. Different Tensional Stress and its
Effects

80. In some instances, parallel faults may
occur in the crust.
The area between two
parallel faults may
eventually sink as the
downward forces act on
it.
The sunken area is called a graben and it
may form rift valley.
The risen area is called a
horst and it may become
a plateau.

81. Types of Faulting

82. We can now conclude that through
great stretches of time, ocean floors
have been lifted up, high areas have
been thruster, pushed down, pushed
and pulled sideways many times.
Careful observations indicate that
these processes are still going on and
affecting the crust.
Where do the forces that shape
the earth come from?

83. Causes of Diastrophism
1. Continental Drift Theory
This theory was
proposed by Alfred
Wegener, a German
scientist in 1915.

84. According to him, 200 million years
ago, there was only a single
supercontinent called Pangaea situated at
the center near the equator.

85. This single
supercontinent
broke up into
pieces which
drifted slowly
away from
each other.
The pieces formed
the continents of
today.
As the continents drifted
apart, they rubbed and collided
against each other forming the
surface features of today.

87. Assignment:
1. Make at least 300 words reaction paper
on the video presentation.
2. Long bond paper.
3. Hand written.
4. Follow the web site below
http://www.youtube.com/watch?v=3HDb9Ijynfo&feature=related

88. 2. The Theory of Seafloor Spreading
In 1920, five years after Wegener’s theory was
formulated, the existence of the mid-oceanic ridges were
discovered using an echo-sounding device like a sonar.

90. A break or rift was found at the middle of the ridge
running along its length where basaltic magma wells out to
the surface.

91. This basaltic magma solidified forming a “new crust”.

92. The new crust pushes the old crust causing the ocean floor to
spread.

93. The force according to theory caused the
breaking and drifting apart of the continents.
The mid-oceanic ridges are believed to be the
remnants of the continents that drifted.
The ocean floor has been estimated to be
spreading at the rate of 5 cm per year.
This rate may seem slow, but for the past 200
million years, all the existing ocean basin were
generated through this slow movement.

94. An exploration using a research ship
named Glomar Challenger drilled through
the crust and gathered several rock
samples from both sides of the mid-
oceanic ridge.

95. Radioactive dating technique
proved that the rocks found from
about the same distance from the
rift on both sides are of the same
age and rock type.
The rocks taken near the ridge
were relatively younger than
those further from the ridge.

96. If new crust is continuously being
formed, does it mean that the earth’s
diameter is expanding?
Scientists explain that as a new crust
is formed at the mid-oceanic
ridges, elsewhere on earth, the old
crust is being destroyed at the same
rate that it is created.
The region where the old crust is
being destroyed is called the
subduction zone.

97. Here in the subduction zone, the old crust is plunged
into high pressure and high temperature
environment.
Thus, some of the materials melt and may migrate
upward giving rise to volcanic eruptions.

98. http://www.youtube.com/watch?v=ep2_axAA9Mw&feature=related

99. 3. The Plate Tectonic Theory
This theory proposed that the
Lithosphere is divided into six major
plates.

100. The plate may be composed of the
continental crust on top of the oceanic
crust or may be composed of the oceanic
crust alone.

101. The plates are slowly, but nevertheless
continually in motion.
The movement of
plates is believed to
be caused by the
convection currents
in the mantle.
As the magma from the lower mantle rises from
deep within the earth and spreads laterally, the
plates are set in motion.
Thus, the movement of the plates generates
earthquakes, volcanic activities, as well as pushes
and pulls causing the deformation of large masses of
rocks.

102. Thus, the movement of
the plates generates
earthquakes, volcanic
activities, as well as
pushes and pulls
causing the deformation
of large masses of rocks.

104. As the movement of the plates goes
on, interaction occurs along their plate
boundaries.
Plate boundary is the place where two plates
meet.

106. The plate boundaries
1. Spreading or divergent boundary
An area where two plates
move apart leaves a gap
between them.
The gap formed is immediately filled up with molten
materials that wells up from the lower mantle.

107. The Atlantic ocean, the Great Rift Valley of Africa and
the Red Sea are believed to be formed by this type of
movement of the plates.

109. 2. Colliding or convergent boundary
This is an area where two plates
move toward each other.
As the plates collide, the
leading edges of one plate is
bent downward allowing it to
slide beneath the other.
As all cases, the denser
materials plunge beneath the
surface.

111. The colliding boundary is the site where the old crust is
being destroyed (subduction zone).
The Himalayan Mountain Ranges, Andes Mountain,
and the Marianas Trench are believed to be formed by
this type of plate movement.

112. Andes Mountain

114. 3. Fracture or transform boundary
This is the area where two plates move past each
other, sliding, scraping and deforming the edges of
continents.

115. The San Andreas Fault of California is a famous example.
The Pacific plate is moving towards
northeast past the North American
plate.
Los Angeles is located on a plate
situated on one side of the fault. San
Francisco is located on another
plate.
In about 10 t0 15 million years, Los
Angeles and San Francisco will be
located next to each other.