Transcript Document

Geology and
Natural Hazards
The Spheres of the Environment
2
3
Chemical composition
of the earth
4
Convection currents are believed
to cause Plate Tectonics
5
6
Earth's tectonic plates
7
that 200 million
years ago
there was a
single
supercontinent
called
Pangaea
that combined
all the world's
continents in a
single
landmass?
8
The Rock Cycle
9
Rocks are assemblages of minerals.
Minerals have a crystalline,
repeating arrangements of atoms,
and a specific chemical composition
Examples of minerals:
quartz (SiO2)
diamond (C)
rock salt (NaCl)
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quartz
feldspar
hornblende
mica
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The rock cycle includes creation, destruction
and metamorphism of rocks
Each of the
three rock
types can be
converted to
either of the
other types
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Igneous Rocks form from magma
(molten rock)
Igneous rocks include:
• volcanic rocks that explosively come to the surface
the earth and cool quickly (lava, basalt)
• magma that cools slowly beneath the surface of the
earth (granite)
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quartz
feldspar
hornblende
GRANITE
mica
Igneous Rock
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Sedimentary Rocks form from
deposition and consolidation
Sedimentary rocks include:
• sandstone and shale
• limestone that precipitated from oceans or seas
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sandstone
shale
mudstone
Some Sedimentary Rocks
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Metamorphic Rocks are rocks that have
been altered by heat and pressure to
make new rocks
Metamorphic rocks include:
• schist
• slate
• marble
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granite
igneous
sedimentary
schist
limestone
shale
marble
slate
metamorphic
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Weathering:
The chemical
and physical
breakdown
of rocks into
their
component
minerals or
elements
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The earth is not a stagnant, unchanging planet-understanding the past environment helps explain the
present and the future
The sun and solar system originated about 5 billion years
ago (bya) when a gas/dust cloud coalesced
The earth is about 4.5 billion years old; the oceans and
atmosphere developed between 3.5 and 4 bya
Since then, oxygen in the atmosphere has increased
tremendously due to:
breakdown of water by ultraviolet radiation
plant photosynthesis
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The Spheres of the Environment
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•
•
Humans have always coped with
‘unpredictable’ natural hazards
Most acts of nature cannot be controlled--we
have learned to better predict the occurrence
of hazards and mitigate their effects
•
Increases in the human population have
increased the effects of ‘disasters’ but
natural
hazards have not changed
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Natural hazards are generally rare,
but normal, natural events.
Natural hazards only become disasters
if people are present.
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Earthquakes
Earthquakes are shock waves that result when
large masses of rock in the earth's crust move
relative to each other; Tsunamis can result from
earthquakes
Volcanoes
Volcanoes are found at places in the earth's
crust where hot, molten rock (magma) wells
up to the surface; found at tectonic plate
boundaries and hot spots
Land Instability
Occurs in many places; includes: landslides,
rockfalls, slumps
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Some earthquakes since the 1500’s
and deaths associated with them
Date
Location
Magnitude
Fatalities
1556
1780
1906
1906
1920
1923
1927
1952
1957
1960
1964
China
Iran
Columbia/Ecuador
San Francisco
China
Kento, Japan
Tsinghai, China
Kamchatka, Russia
Andreanof Is., Alaska
Chile
Prince William Sound, Alaska
~8
Unknown
8.8
7.8
8.6
7.9
7.9
9.0
9.1
9.5
9.2
~800,000
~200,000
1,000
3,000
200,000
143,000
200,000
unknown
unknown
5,700
125
1976
Tangshan, China
7.5
> 255,000
1995
Kobe, Japan
6.9
5,500
2001
2002
2004
Olympia, Washington
Afghanistan
Sumatra
6.8
6.1
9.0
0
10,000
?? or >250,000 25
Kobe, Japan,1995; magnitude 7.
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Issaquah, February 2001; magnitude 6.8
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Bam, Iran
December 2003
magnitude 6.6
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Earthquake of magnitude 9.0 strikes NW Sumatra, December 2004
This is the largest earthquake since the 1964 Prince William Sound, Alaska earthquake.
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Tsunami at Phuket, Thailand
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Mt. St. Helens
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California hillside and English coast
Barrier Island coast
Impacts of a jetty on beach
sand deposition and erosion
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Tropical cyclones, hurricanes and typhoons are intense
storms that develop over warm tropical areas.
Tornadoes are a rapidly rotating vortice of air that forms
a funnel. When they touch the ground, they can be one
of the most deadly natural hazards.
Floods can be nothing more than a normal but not
frequent natural occurrence but seem disastrous from a
human perspective. Cumulatively, floods are among the
most destructive of natural hazards.
Wildfire
Coastal storm surges
Drought (1988 drought – est. cost of 39 Billion $)
Hail
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Mississippi River, Davenport Iowa, 1993
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Hurricane Andrew, before
hitting the Florida coast
and its aftermath
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Estimated deaths and damages caused by
hurricanes since 1900
10000
8000
Deaths
6000
4000
2000
0
Damage
in
Billions
of
Dollars
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
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30
25
20
15
10
5
0
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Severe weather, such as tornadoes
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Canberra, ACT, Australia, 2002
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Estimated deaths from natural hazards
during 1960 to 2000
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Estimated deaths from natural hazards
during 1960 to 2000
850,000
650,000
60,000
50,000
36,000
(tropical storm)
(earthquake)
(flood)
(slides)
(volcano)
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The earth is complex and old (~4.5 by)
Earth’s crust differs from its core
Plate tectonics reorganizes the earth’s surfaceAs does the rock cycle (the interchange of
three
kinds of rocks:
igneous
metamorphic
sedimentary
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The earth is dynamic--natural hazards occur
Hazards include:
earthquakes, tsunamis
volcanoes, landslides
hurricanes and other
storms
floods, wildfires
Hazards only become disasters
when people are involved
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