Transcript 0004 Earth Characteristics and Processes

0004 Earth Characteristics and Processes:
1. demonstrate knowledge of the earth's structure and
composition.
Basic Structure of the Earth
• 8,000 miles in diameter
• lithosphere, hydrosphere, atmosphere
• 4 spherical regions:
– crust, mantle, outer core, inner core
Earth Structure
0004 Earth Characteristics and Processes: 2. classify
rocks and minerals based on their process of formation and
characteristics.
What are Rocks? What are Minerals?
• Rocks
• Minerals
• An aggregate or
mixture of minerals.
• Composition can vary
• Most rocks are
composed of more
than one mineral
• building blocks of
rocks; elements or
compounds found in
the Earth’s crust.
• > 3000 minerals
differing in properties
link
Rocks
• Igneous = formed by the cooling and
crystallization of magma (melted rock)
• Sedimentary = formed from accumulation
of weathered material (sediments)
• Metamorphic = formed from preexisting
rocks that have been transformed (changed)
Igneous, Sedimentary, Metamorphic
 Each type of rock records a different
complex past.
 Each type of rock can be changed from
one form to another and back again.
 geologists call these transformations the
“rock cycle”
Rock Cycle
Crystal Form
• Pyrite, Fe2S
• Quartz, SiO2
Moh’s Hardness Scale
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•
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1.Talc
2.Gypsum
3.Clacite
4.Fluorite
5.Apatite
• 6.Orthoclase
• 7.Quartz
• 8.Topaz
• 9.Corundum
• 10.Diamond
Cleavage & Fracture
Physical Properties of Minerals
• Crystal form
• Hardness
• Plane of Cleavage
• Luster
• Color and Streak
• Specific Gravity
Igneous Rock
 formed by cooling & crystallization
of magma.
 means “formed by fire”
 make up about 95% of the earth’s crust
 basalt (ocean floor) and granite (continents)
are common examples
Sedimentary Rock
 formed from the weathered material
carried by water, wind, or ice
 most common rocks in the upper crust
 cover over 2/3 of the earth’s surface
 sandstone, shale, and limestone
Metamorphic Rock
• ---formed from preexisting rocks (igneous,
sedimentary, or other metamorphic)
• ----metamorphic means “changing in form”
• ----marble and slate are common examples
0004 Earth Characteristics and Processes: 3. identify the
characteristics of soil and analyze how it forms.
0004 Earth Characteristics and Processes: 4. analyze
constructive and destructive processes that form and change
major geological features (e.g., tectonic movements, erosion,
deposition).
0004 Earth Characteristics and Processes:
5. demonstrate knowledge of the theory of plate tectonics
and evidence that supports the theory.
October 17, 1989
May 18, 1980
Earthquakes and volcanoes: evidence
that our planet is not at rest.
• global distribution of earthquakes and
volcanic centers…above crustal plate
boundaries
• The surface of the earth is constantly
changing and no feature on earth is
permanent.
Why is the Earth so restless?
• “Convection Conveyer-belt”
• The heat that drives the motion of the
mantle comes from two sources:
---Radioactive decay of materials in the
mantle
---Heat left over from the formation of the
earth
James Hutton 1726-1797
• "catastrophism,"
earthly changes were
sudden & caused by a
series of catastrophes
• This belief prevailed
until the 1700s
• "uniformitarianism
• 1785 James Hutton
• The present is the key
to the past
Uniformitarian Principle
• the geologic forces and processes -gradual as well as catastrophic -- acting
on the Earth today are the same as those
that have acted in the geologic past.
Alfred Wegener 1880-1930
Theory of Continental Drift
• (Wegener, 1915)
• continents plowed through crust of ocean
basins, which would explain why the
outlines of many coastlines(like South
America and Africa) look like they fit
together like a puzzle
Continental Drift:
a theory ahead of its time
• impossible for a large mass of solid rock to
plow through the ocean floor without
breaking up
• mid 20th Century, new evidence from
ocean floor exploration rekindled interest
in Wegener's theory, ultimately leading to
theory of plate tectonics.
Plate Tectonics: A modern version of
Wegener’s old idea
• the outer rigid lithosphere consists of about
20 rigid segments called plates
• Most plates contain both continental and
oceanic crust—a major departure from the
continental drift theory
• The word tectonics comes from the Greek
root "to build."
Folding and Faulting
• Compressive forces from moving plates
can cause rock to bend & wrinkle into
wavelike folds
• The crack or break in the rock is called a
fault and the movement of the rock is
“faulting”
Earthquakes
• Great forces of stress occurs as plates of
rock pushed in opposite directions
• sudden movement as the blocks slide and
then come to rest in a new position that
eases the pressure
The entire San Andreas fault system is more than
800 miles long and extends to depths of at least 10
miles within the Earth. In detail, the fault is a
complex zone of crushed and broken rock from a
few hundred feet to a mile wide.
Seismograph
• Richter Scale based on the amount of
seismographic movement
• An earthquake with a number of 2 is just
strong enough to be felt, 5 can cause much
damage, 7 or more is classified as a major
earthquake
Plate Boundaries
• 3 Main Types
–Divergent
–Convergent
–Transform
Divergent Plate Boundaries
• plates are being pulled apart
• sea floor spreading at Mid-Atlantic Ridge
• Eurasia and North America are separating
at a rate of about 5 cm per year
• East African Rift Valley
Convergent Plate Boundaries
• two plates are coming together
• 3 associated surface feature
– deep ocean trench and chain of volcanic
islands
– folded mountains
– ocean plate subduction beneath continent
Transform Plate Boundaries
• one plate scrapes past the other
• San Andreas fault in California
• No mountain building or volcanism is
associated with transform boundaries.
0004 Earth Characteristics and Processes: 6. recognize
characteristics of fossils and how they show evidence of the
changing surface and climate of the earth.