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Rock Cycle formation of different rock This
cycle is involved with three types of rock a.
Sedimentary b. Metamorphic c. Igneous
schematic diagram rock cycle
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Sedimentary Rock a. occurs near the Earths
surface b. sediment settles to the bottom of the
rivers, lakes, and oceans c. forms in
layers called strata or stratification
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Sedimentary Rock Cycle a. weather breaks
down existing rock b. deposition c.
compaction and cementation
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Metamorphic Rock a rock type that has changed
into another type a. occurs 2 to 16km deep in
the Earth b. pressure is almost 4,000 times
greater than at the surface c. temperature
ranges from 1500C to 10000C
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Composition of Metamorphic rock heat and
pressure play the significant roles in forming
this type of rock
Minerals Heat and Pressure New mineral
New minerals formed at different temperatures at
different depths
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Igneous Rock formed from the cooling of
magma a. melted rock is trapped in the earth
then cools b. lava from a volcano erupts and
then cools
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Three ways that rock can become magma a.
Temperature b. Pressure c. Composition
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Igneous Rock formations
Two process in which magma forms rock 1.
Intrusive coarse grained rock that developed
after magma has cooled below the Earths
surface
after weathering of Earth's surface, these
intrusions are apparent
Shiprock, New Mexico
Devils Tower
extinct volcano
dike
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2. Extrusive rock very small crystalline rock
that is formed on the Earths surface called
lava or under the oceans surface,
pillow lava
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Earths story Two theories on the geologic
processes which points to how the Earths
landscape was/is formed 1. Uniformitarianism
James Hutton, 1795 developed the idea the
landscape developed over long periods of
time through a variety of slow geologic and
geomorphic processes. a. deep soil profiles
were formed by the weathering of
bedrock over thousands of years b. slow uplift
and subsidence of land surfaces cause
changing topography
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2. Catastrophism - doctrine that the geological
changes in the earth's crust have been
caused by the sudden action of violent
physical causes a. biblical floods b.
asteroid impacts
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Relative dating (and I am not referring to my
family tree) uses the Principal of
Superposition a. It is based on sedimentary
rocks and fossils b. Oldest layers are at the
bottom c. Helps in the order of events d.
Produces a geologic column
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The Geologic column can have some very
interesting formations. a. Faults - a crack in
the earth's crust resulting from the
displacement of one side with respect to
the other
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b. Intrusion molten rock that seeps into
crevices and cools
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c. Folding rock layers bend and buckle
from internal forces
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d. Tilting internal pressures slants the
geologic column without folding
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Unconformity a missing part of the geologic
column mostly occurs due to a.
deposition b. erosion Three types of
unconformities a. disconformity rock layer is
missing
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b. Nonconformity sedimentary layer sits on
top igneous or metamorphic rock
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c. Angular unconformity layer between
horizontal layer and tilted rock layer
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Absolute Dating a process which establishes the
age of an object The process uses radioactive
decay the decay works this way Unstable atoms
turn into stable atoms Parent isotope unstable
isotope Daughter isotope stable isotope
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Radiometric dating percentage of parent unstable
isotope to daughter stable isotope Uses
half-life of isotope to date object Three
methods of radiometric dating a. Uranium-lead
method b. Potassium-argon method c. Carbon-14
method
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The Earth may be described in two ways 1.
Composition 2. Physical properties Lets take a
look at each one 1. Composition - the Earth is
composed of three layers a. Crust outermost
layer b. Mantle middle layer c. Inner and
outer cores
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There are two categories of crust a. Continental
about 30 km thick granite b. Oceanic about7
km thick basalt
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2. Physical properties a. Lithosphere
outermost layer (tectonic plates) made up of 1.
crust 2. upper part of mantle b.
Asthenosphere soft part of mantle c.
Mesosphere strong part of mantle,
extends from asthenosphere to outer core d.
Outer core liquid layer of core e. Inner core
solid core
6 miles
60 miles
125 miles
400 miles
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Rock a little geology lesson!!! Earth is made
up of four layers a. inner core - mass of iron
with a temperature of 70000 F b. outer
core - electrical currents generated from
this area produce the earth's magnetic field.
c. mantle - slow moving molten rock or magma,
20000 F d. crust - layer from 4-25 miles thick
consisting of sand and rock
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Mapping the Earth layers a seismograph can be
used to measure the thickness of each layer
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The lithosphere is made up of tectonic plates
these are plates that float on the asthenosphere
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Cross section of a tectonic plate
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Continental Drift Wegener, Alfred 1880 - 1930
theory that all of the worlds land masses
were at one time together !!!!! called the land
mass Pangaea about 245 million years
ago Evidence a. continents fit together like a
puzzle b. identical fossils on one continent are
found on another e.g. plants on S.
America, Africa, Antarctica and Australia c.
glaciers
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Are the continents on the move??? Yes, about 2
to 3 inches per year How you ask... Sea-floor
Spreading!!! As the continents move apart the
mid-ocean ridge pulls apart and molten rock
fills the gap

That is how the geologists determine the age of
the ocean floor
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As the magma makes new sea floor, the magnetic
poles actually change direction At irregular
intervals, averaging about 200-thousand years,
the Earth's magnetic field reverses. The end of
a compass needle that today points to the north
will instead point to the south after the next
reversal.
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Theory of Tectonic Plates
Two possible answers for tectonic plate
shift a. gravity b. heat
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