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Introduction to Geology
Definition: Geology -the study of the
has undergone and is
, its form and
, and the changes which it
2 main branches of geology:
1.
-examines the materials of the Earth and seeks to
understand the processes and forces acting beneath upon the Earth’s surface
2.
-involves the study of
-examines the origin of the Earth and its development through time
and their sequence in rock beds
-must understand
before studying Earth history
-Aristotle’s notions of geology erroneous, but widely accepted for centuries
Definition: Catastrophism –
-catastrophists believed Earth was only approx. 6000 years old
Definition: Uniformitarianism –
-first proposed in late 1700’s by
-later supported and advanced by
(“father of modern geology”)
in 1800’s
-not all geological processes hold same importance and operate at same rate through
different time periods
-Earth is approx. 4.6 billion years old
-use
to age Earth
Definition: Radiometric Dating -procedure of
Geologic Time Scale:
-geologic time scale developed using relative dating
Defintion: Relative Dating –
-use law of superposition
Definition: Law of Superposition
-in any
sequence of sedimentary rocks or
surface-deposited igneous materials, each layer is
than the one above it and
than the one below it
-fossils are essential for
Definition: Fossils Definition: Principle of Faunal (Fossil) Succession -fossil organisms
one another
in a definite and determinable order, and any time period can
be recognized by its
-different units of time and duration depend on the amount and variety of fossils
found in a particular period
Structure of the Earth:
-environment divided into 4 major parts (or “spheres”):
1. Atmosphere
-region of air (78% N2; 21% O2) for breathing and protection from
Sun’s harmful radiation
-energy exchanges between atmosphere & earth’s surface and atmosphere &
space produce
2. Hydrosphere
-region of
(ie. oceans, lakes, glaciers, groundwater)
-water continually moves from ocean to air to land and back to ocean (
cycle)
3. Geosphere -divided into 4 major
regions:
A.
-light, outer shell;
thick (least dense)
km
B.
-solid/fluid, rocky
layer; max. thickness of
km (more
dense)
C. outer core -molten, metallic layer;
km thick
D. inner core -solid, iron-rich layer;
radius of
km
4. Biosphere – all life on Earth
Definition: Lithosphere
(“sphere of rock”)
-includes the
and
uppermost
approx. 100 km)
(down to
Definiton: Asthenosphere
weak zone capable of
-hot,
-located between 100 – 700 km
below lithosphere
The Theory of Plate Tectonics:
-Earth driven by
(or devices that convert heat energy to mechanical energy)
-2 heat engines:
-external heat engine provides energy for atmospheric and oceanic circulation (weather & climate)
-internal heat engine driven by heat for hot interior moving toward the cooler exterior; it produces
moving continental plates and earthquakes
-rock deep inside Earth can deform under intense
-hot, less dense rock rises slowly toward surface
-cooler,
rock at surface sinks downward
-this process repeats to form a
Rising hot, less dense rock
Falling cool, more dense rock
Definition:
Theory of Plate Tectonics
-theory that proposes that
Earth’s outer shell consists
of
-originally proposed by
(1912)
-based on earlier theory of
-plate tectonic theory used to
explain geological
and events
-lithosphere broken into individual pieces called
-plates are constantly in
-motion caused by internal
-as hot material moves upward, it
-this movement generates
,
(see above)
and
Definition: Orogenesis
-periods of intense
-results in
Interactions Between Tectonic Plates:
-3 types of plate boundaries:
1.
boundaries
– zones where plates
, leaving a gap between them
–
occurs where gap fills with molten rock and cools, repeatedly
adding more oceanic lithosphere
2.
boundaries
– zones where plates
, causing one to go beneath the
other (oceanic crust) OR where plate collide (continental crust)
–
occur where oceanic lithosphere is being consumed
– as a plate moves downward, subducted material melts under high temperature and
pressure and moves up to overriding plate (
activity)
3.
boundaries
– zones where plates
– earthquake activity occurs
, scraping and deforming as they pass
The Rock Cycle:
-concept map that explains origin of 3 basic rock types:
Definition: Igneous rock -rock that forms by the crystallization of
Definition: Magma -
,
, and
Definition: Crystallization -the formation and growth of a
-igneous undergo weathering
Definition: Weathering -the disintegration and
surface of the Earth
of rock
the
-the weathered material is picked up, transported and deposited by agents of erosion
Definition: Erosion –
Definition: Sediment -loose particles created by
of rock, by chemical
from solution in water, or from the secretions of organisms, and
transported by water,wind or ice
-sediment is deposited in beds and undergo
to form sedimentary rock
Definition: Lithification -the process of converting
to
-if sedimentary rock is buried deep in Earth or involved in orogenesis, great pressures
and heat will form
-metamorphic rock can then form igneous rock (magma) under increased pressure and
heat
-“shortcuts” in rock cycle model:


-rock cycle first proposed by
-very little known about rock formation
-later plate tectonics used to explain cycle
The Rock Cycle
______________________________________________________________________
The Rock Cycle as it relates to the Theory of
Plate Tectonics