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COMPETENCY 1.O GEOLOGY
SKILL 1.1
Identify the layers of the earth by position on a diagram.
The earth’s physical enviroment is divided into three major parts: the
atmosphere:, the hydrosphere, and the lithoshpere: The atmosphere is the layer
of air that surrounds the earth. The hydrosphere is the water portion of the planet
(70% of the earth is covered by water) and the lithosphere is the solid portion of
the earth.
The earth’s layered structure includes: the crust, mantle, outer core, and the
inner core.
SKILL 1.2
Identify physical and chemical characteristics of the earth’s
layers.
The crust is the thinnest layer. Its thickness varies and is thickest when located
under the continents and thinnest under the oceans.
The boundary separating the crust from the mantle is known as the Mohorovic
Discountinity, named after the discovering scientist. It is commonly called the
Moho.
The Mantle is located directly beneath the crust. Mantle rocks are dense and
contain more iron than those rocks contained in the crust.
The outer core is composed of iron and nickle. Geologists think the outer core is
a hot molten liquid..
The inner core is probably an iron nickle solid core because of the intense
pressure exerted by the surrounding zones.
Rocks are made up of minerals consisting of chemical elements or chemical
compounds.
A chemical element is the simplest kind of substance. A chemical element can
not be broken down into simpler substances by ordinary means. Gold, silver,
oxygen and carbon are examples of chemical elements.
A chemical compound consists of two or more elements combined in fixed
proportions by weight. Salt, water, table salt and natural gas are examples of
chemical compounds.
Elements in the earth’s crust are combinations of 88 different elements. Three
common groups of minerals in the earth’s crust are silicates, carbonates and
oxides.
The two most common abundant elements in the earth’s crust are; oxygen and
silicon.
The eight major elements in the earth’s crust:
ELEMENT
WEIGHT
Oxygen
Silicon
Aluminum
Iron
Calcium
Sodium
Potasium
Magnesium
SKILL 1.3
SYMBOL
APPROX. % BY
O2
Si
Al
Fe
Ca
Na
K
Mg
47
28
8
5
4
3
3
2
Types of mountains and volcanoes with related terminology
Orogeny is the term given to natural mountain formation.
A mountain is terrain that has been raised high above the surrounding landscape
by volcanic action, or some form of techtonic plate collisions. The plate collisions
could be inter continental or ocean floor collisions with a continental crust
(subduction).. The physical conposition of mountains would include igneous,
metamorphic, or sedimentary rocks; some may have rock layers that are tilted or
distorted by plate collision forces.
There are many different types of mountains. They are The physical attributes of
a mountain range depends upon the angle at which plate movement thrust layers
of rock to the surface. Many mountains (Adirondacs, Souther Rockies) were
formed along high angle faults.
Folded mountains (Alps, Himalayas) are produced by the folding of rock layers
during their formation. The Himalayas are the highest mountains in the world and
contains Mount Everest which rises almost 9 km above sea level. The Himalayas
were formed when India collided with Asia. The movement which created this
collision is still in process at the rate of a few centimeters per year.
Fault-block mountains (Utah, Arizona, New Mexico) are created when plate
movement produces tension forces instead of compression forces. The area
under tension produces normal faults and rock along these faults and is
displaced upward.
Dome mountains are formed as magma tries to push up through the crust but
fails to break the surface. Dome mountains resemble a huge blister on the
earth’s surface.
Upwarped mountains (Black Hills of S.D.) are created in association with a broad
arching of the crust. They can also be formed by rock thrust upward along high
angle faults.
Volcanic mountains are built up by successive deposits of volcanic materials.
Vulcanism is the term given to the movement of magma through the crust and its
emergence as lava onto the earth’s surface.
An active volcano is one that is presently erupting or building to an eruption. A
dormant volcano is one that is between eruptions but still shows signs of internal
activity that might lead to an eruption in the future. An extinct volcano is said to
be no longer capable of erupting. Most of the world’s active volcanoes are found
along the rim of the Pacific Ocean, which is also a major earthquake zone. This
curving belt of active faults and volcanoes is often called the Ring of Fire.
The world’s best known volcanic mountains include: Mount Etna in Sicily and
Mount Kilimanjaro in Africa. The Hawaiian islands are actually the tops of a chain
of volcanic mountains that rise from the ocean floor.
There are three types of volcanic mountains: shield volcanoes, cinder cones and
composite volcanoes.
Shield Volcanoes are associated with quiet eruptions. Lava emerges from the
vent or opening in the crater and flows freely out over the earth’s surface until it
cools and hardens into a layer of igneous rock. Repeated lava flows builds this
type of volcanoe into the largest volcanic mountain. Mauna Loa found in Hawaii,
is the largest volcano on earth.
Cinder Cone Volcanoes associated with explosive eruptions as lava is hurled
high into the air in a spray of droplets of various sizes. These droplets cool and
harden into cinders and particles of ash before falling to the ground. The ash and
cinder pile up around the vent to form a steep, cone-shaped hill called the cinder
cone. Cinder cone volcanoes are relatively small but may form quite rapidly.
Composite Volcanoes are described as being built by both lava flows and
layers of ash and cinders. Mount Fuji in Japan, Mount St. Helens in Washington,
USA and Mount Vesuvius in Itlay are all famous Composite Volcanoes.
SKILL 1.4 Knowledge of folds, including terminology
Mountains are produced by different types of mountain-building processes. Most
major mountain ranges are formed by the processes of folding and faulting.
Folded Mountains are produced by folding of rock layers. Crustal movements
may press horizontal layers of sedimentary rock together from the sides,
squeezing them into wavelike folds. Upfolded sections of rock are called
anticlines; downfolded sections of rock are called synclines.
The Appalachian Mountains are an example of folded mountains with long ridges
and valleys in a series of anticlines and synclines formed by folded rock layers.
SKILL 1.5 Knowledge of faults and terminology
Faults are fractures in the earth’s crust which have been created by either
tension or compression forces transmitted through the crust. These forces are
produced by the movement of separate blocks of crust.
Faultings are categorized on the basis of the relative movement between the
blocks on both sides of the fault plane. The movement can be horizontal, vertical
or oblique.
A dip-slip fault occurs when the movement of the plates are vertical and
opposite. The displacement is in the direction of the inclination, or dip, of the
fault. Dip-slip faults are classified as normal faults when the rock above the fault
plane moves down relative to the rock below.
Reverse faults are created when the rock above the fault plane moves up
relative to the rock below. Reverse faults having a very low angle to the
horizontal are also referred to as thrust faults.
Faults in which the dominant displacement horizontal movement along the trend
or strike (length) of the fault, are called strike-slip faults. When a large strike-slip
fault is associated with plate boundaries it is called a transform fault. The San
Andreas fault in California is a well-known transform fault.
Faults that have both vertical and horizontal movement are called oblique-slip
faults.
When lava cools, igneous rock is formed. This formation can occur either above
ground or below ground.
Intrusive rock includes any igneous rock that was formed below the earth’s
surface.
Batholiths are the largest structures of intrusive type rock and are composed of
near granite materials; they are the core of the Sierra Nevada Mountains.
Extrusive rock includes any igneous rock that was formed at the earth’s surface
Dikes are old lava tubes formed when magma entered a vertical fracture and
hardened. Sometimes magma squeezes between two rock layers and hardens
into a thin horizontal sheet called a sill. A laccolith is formed in much the same
way as a sill, but the magma that creates a lacclith is very thick and does not flow
easily. It pools and forces the overlying strat creating an obvious surface dome.
A caldera is normally formed by the collapse of the top of a volcano. This
collapse can be caused by a massive explosion that destroys the cone and
empties most if not all of the magma chamber below the volcano. The cone
collapses into the empty magma chamber forming a caldera..
An inactive volcanoe may have magma solidified in its pipe. This structure, called
a volcanic neck, is resistant to erosion and today may be the only visible
evidence of the past presence of an active volcano.
Skill 1.6 Knowledge of intrusive and extrusive activities including
terminology.
When lava cools, igneous rock is formed. This formation can occur either above
ground or below ground.
Intrusive rock includes any igneous rock that was formed below the earth's
surface. Batholiths are the largest structures of intrusive type rock and are
composed of near granite materials; they are the core of the Sierra Nevada
Mountains.
Extrusive rock includes any igneous rock that was formed at the earth's surface.
Dikes are old lava tubes formed when magma entered a vertical fracture and
hardened. Sometimes magma squeezes between two rock layers and hardens
into a thin horizontal sheet called a sill. A laccolith is formed in much the same
way as a sill, but the magma that creates a laccolith is very thick and does not
flow easily. It pools and forces the overlying strata creating an obvious surface
dome.
A caldera is normally formed by the collapse of the top of a volcano. This
collapse can be caused by a massive explosion that destroys the cone and
empties most if not all of the magma chamber below the volcano. The cone
collapses info the empty magma chamber forming a caldera.
An inactive volcano may have magma solidified in its pipe. This structure, called
a volcanic neck, is resistant to erosion and today may be the only visible
evidence of the past presence of an active volcano.
Skill 1.7 Knowledge of major plates on the earth and their mechanisms and
motions.
Plate Collisions. boundaries between plates that are colliding are zones of
intense crustal activity. When a plate of ocean crust collides with a plate of
continental crust, the denser oceanic plate slides under the lighter continental
plate and plunges into the mantle. This process is called subduction, and the
site where it takes place is called a subduction zone.
A subduction zone is usually seen on the sea-floor as a deep depression called a
trench.
In addition to separating and colliding, crustal plates may interact by sliding
sideways past each other. This motion produces a plate boundary characterized
by major faults that are capable of unleashing powerful earthquakes.
The theory of plate tectonics explains why most crustal activity occurs in long
belts. These zones of earthquakes, vulcanism, and mountain-building mark the
boundaries between the crustal plates.
SKILL 1.8 Knowledge of plate boundary structures and processes.
Data obtained from many sources led scientists to develop the theory of plate
tectonics. This theory is the most current model that explains not only the
movement of the continents, but also the changes in the earth’s crust caused by
internal forces.
Plates are rigid blocks of earth’s crust and upper mantle. These rigid solid blocks
make up the lithosphere. The earth’s lithosphere is broken into nine large
sections and several small ones. These moving slabs are called plates. The
major plates are named after the continents they are “transporting.” (See figure
1.7)
The plates float on and move with a layer of hot, plastic-like rock in the upper
mantle. Geologists believe that the heat currents circulating within the mantle
cause this plastic zone of rock to slowly flow, carrying along the overlying crustal
plates.
Movement of these crustal plates creates areas where the plates diverge as well
as areas where the plates converge. In the Mid-Atlantic is a major area of
divergence. Currents of hot mantle rock rise and separate at this point of
divergence creating new oceanic crust at the rate of 2 to 10 centimeters per year.
Convergence is when the oceanic crust collides with either another oceanic plate
or a continental plate. The oceanic crust sinks forming an enormous trench and
generating volconic activity. Convergence also includes continent to continent
plate collisions..When two plates slide past one another a transform fault is
created.
These movements produce many major features of the earth’s surface, such as
mountain ranges, volcanoes, and earthquake zones. Most of these features are
located at plate boundaries, where the plates interact by either spreading apart,
pressing together, or sliding past each other. These movements are very slow,
averaging only a few centimeters a year.
Boundaries form between spreading plates where the crust is forced apart in a
process called rifting. Rifting generally occurs at mid-ocean ridges. Rifting can
also take place within a continent, splitting the continent into smaller, landmasses
that drift away from each other, thereby forming an ocean basin (Red Sea)
between them. As the seafloor spreading takes place, new material is added to
the inner edges of the separating plates. In this way, the plates grow larger, and
the ocean basin widens. This is the process that broke up the supercontinent
Pangaea and created the Atlantic Ocean.
Boundaries between plates that are colliding are zones of intense crustal activity.
When a plate of ocean crust collides with a plate of continental crust, the more
dense oceanic plate slides under the lighter continental plate and plunges into
the mantle. This process is called subduction, and the site where it takes place is
called a subduction zone. A subduction zone is usually seen on the sea-floor as
a deep depression called a trench.
The crustal movement which is characterized by plates sliding sideways past
each other produces a plate boundary characterized by major faults that are
capable of unleashing powerful earth-quakes. The San Andreas Fault forms such
a boundary between the Pacific Plate and the North American Plate.
SKILL 1.9
Identify geological evidence supporting the theory of plate
tectonics.
Alfred Wegener proposed that crustal movements have taken place on a global
scale. He suggested that a “supercontinent” which he called Pangaea once was
made up of all the present day continents. Eventually, Pangaea split up, and the
continents drifted apart, forming the Atlantic Ocean. Evidence supporting this
theory consisted of matching coastlines, plant and animal equivalents on different
continents, and matching rock and mountain range characteristics..
Wegener’s hypothesis of continental drift was rejected by most scientists
because it did not adequately explain how the continents could move across the
solid rock of the ocean floor. However, in the 1960’s scientists studying the
ocean floor made several discoveries that supported the idea of moving
continents.
Surveys of the ocean floor had revealed a long mountain chain running down the
center of the Atlantic Ocean, called the Mid-Atlantic Ridge Samples of ocean
crust from the ridge were determined to be made up of very young volcanic
rock.It was also determined that the ocean crust becomes progressively older as
its distance from the ridge crest increases. These findings proved that the
seafloor is contunually spreading apart at the Mid-Atlantic Ridge. Molten rock
rises into a deep narrow rift valley along the crest of the ridge. This rift cools to
form new ocean crust The discovery of this ongoing process, called seafloor
spreading, helped solve the problem of how the continents move.
SKILL 1.10
Knowledge of terminology related to earthquakes
Earthquakes can occur in the ocean and cause fast-moving ocean waves called
tsunamis. Earthquakes on land occur in areas called earthquake belts,
extensive areas with crustal activity. The area where rocks fracture is the origin
of seismic waves. The focus is located underground. The epicenter is located
above the ground.
SKILL 1.11
Knowledge of causes and effect of earthquakes
Forces within the earth push, pull, and twist the rocks that make up the crust.
When these forces become too great, the crust breaks, or fractures. These
broken sections of earth’s crust vibrate as the tension is released and the fault
line relaxes. This vibrating of the crust is an earthquake.
A fracture in earth’s crust along which sections of the crust slide past each other
is called a fault. The movement of the rocks along a fault is called slippage. Most
of California’s earthquakes are caused by slippage of the crust along the San
Andreas Fault
Tsunamis are fast-moving ocean waves caused by earthquakes that occur on the
seafloor. A Tsunami usually gives warning before it strikes. Minutes before a
large tsunami arrives, the water near the shore suddenly drains seaward,
exposing parts of the beach normally submerged. Then, with a hissing sound, the
wave rushes across the waterless beach and strikes the shore with a great roar,
pounding the shore for several hours.
SKILL 1.12 Earthquake wave sequence and types
Earthquakes produce measurable waves that are transmitted through the earth’s
crust and interior. The major classification of waves is 1) surface waves and 2)
body waves. Suface waves travel through the upper layer of the earth’s crust;
body waves travel through the earth’s interior. The latter classification , body
waves, is further broken down into two additional categories. These are P or
primary waves and S or secondary waves.
P waves compress and expand the material through which they travel. S waves,
on the other hand, oscillate up and down like an ocean wave. The movement of
surface waves is a combination of up and down oscillations plus a sideways
oscillation. This sideways oscillation causes most of the structural damage during
an earthquake.
SKILL 1.13 Locate earthquakes from seismographic data
When rocks fracture and slip along a fault, earth’s crust vibrates. The vibrations
travel through earth as seismic waves.
The denser the material, the faster a seismic wave moves through it.
Seismic waves from earthquakes can be detected and recorded by using an
instrument called a seismograph.
A record of the earthquake is called a seismogram.
A seismograph can detect an earthquake that occurs thousands of kilometers
away. The point where rocks first fracture is the source of seismic waves.
Located underground, this point is the focus of the earthquake. The point on
earth’s surface directly above the focus is called the epicenter. Most earthquakes
occur within 50 km of earth’s surface.
The Richter scale measures the magnitude of earthquake waves.
SKILL 1.14 States of matter, including plasma.
Matter is found in four states; solid, liquid, gas, and plasma. The four states of
matter all consist of particles in motion.
A solid is defined as a crystalline matter with a definite volume and shape.
Particles in a solid state form a regular repeating pattern and are constantly
vibrating.
A liquid is defined as a definite volume and shape that takes on the shape of its
container. Particles move freely about each other.
A gas has no definite shape or volume. Particles move rapidly and freely.
Plasma is matter that consists of charged particles. Over 99 percent of the matter
in the universe is in the plasma state. Plasma occurs where temperatures are
very high and where matter consists of positive and negative particles. Plasma
will conduct electricity. The matter in fluorescent tubes is plasma. The outer layer
of the atmosphere that surrounds earth is in a plasma state. This layer aids in
communication.
SKILL 1.15 Define atom, ion, elements, compounds, minerals, ores, rock
and rock faces.
An atom is the building block of matter. The smallest unit of an element that still
keeps the properties of the element.
An ion is defined as an atom or group of atoms that has gained or lost an
electron.
An element is a substance made of just one type of atom.
Scientists organize elements into a table called the Periodic Table. Elements are
listed in the table in order of atomic number. Each element is represented by a
symbol. The first letter is always a capital letter. The second letter and third letter
are lower case. Examples include: Hydrogen (H), Gold (Au).
Compounds are substances made of two or more elements whose atoms are
chemically combined.
Minerals are natural, non-living solids with a definite chemical composition and a
crystalline structure.
Ores are minerals or rock deposits that can be mined for a profit.
Rock - Earth materials made of one or more minerals.
Rock Facies - A rock group that differs from comparable rocks (as in
composition, age or fossil content).