Transcript Inside Earth

UNIT:
Inside Earth
Geologists
• Scientists that
study the
processes that
create Earth’s
features and the
Earth’s History
Forces That Shape Earth’s
Surface: Destructive Forces
• The forces that
slowly wear away
the Earth’s surface
• Examples:
Weathering and
Erosion (Mass
Wasting, Rivers,
Glaciers, Wind,
Waves)
Forces that Shape the Earth’s
Surface: Constructive Forces
• Forces that build
up the Earth’s
surface
• Examples:
Earthquakes,
plate tectonics,
volcanoes, etc
How do Scientists Know what is
inside the Earth?
• Scientists use indirect evidence to
determine what is inside the Earth
• earthquake waves (SEISMIC WAVES)
help determine what is in the Earth
• Seismic waves change speed or stop
when they enter different materials
• This shows that Earth is made of layers
Earth’s characteristics change as
you travel toward her center.
• TEMPERATURE: increases with depth
• PRESSURE: increases with depth
Layers Within the Earth
• The Earth possesses three main
layers:
• Crust, Mantle, and Core
The Crust
• Earth’s outermost
layer
• Made up of ocean
crust-Basalt
• Made up of
continental crustgranite
• Rigid rocky layer of
Earth
The Mantle
• The second layer within
the Earth
• 5 to 40 Km below the
surface
• Asthenosphere: upper
layer of the mantle that is
“plastic” in nature
• The plates that carry the
continents “float” on the
asthenosphere
The Core
• Made of two layers-the outer
core and the inner core
• Outer Core:
liquid sphere of
molten nickel
and iron
Inner Core: solid
ball of nickel and
iron
Earth’s Magnetic Field
• Earth acts as a
magnet in space
• It has both a North
and South pole
• caused by fluid
movements in Earth’s
liquid outer core
causing the solid
inner core to spin
Inside Earth
Chapter 1
Section 2: Convection
Currents
in the Mantle
Heat Transfer
• The movement
of heat from
warmer locations
to cooler ones
• 3 Types:
– Radiation
– Conduction
– Convection
3 Types of Heat Transfer:
Radiation
• Transfer of heat through empty space
• No direct contact between particles is required.
Does not need a solid liquid or gas.
• Example: Heat from a fire moving sideways,
heat from the sun moving through space
3 Types of Heat Transfer:
Conduction
• The transfer of heat by collisions between
atoms and molecules. Best in solids!
• Example: a spoon becomes hot when in a
pot of soup, burning your hand when you
touch a curling iron
3 Types of Heat Transfer:
Convection
• Heat transfer through movement of hot fluids
because of density differences.
• heated particles begin to flow from one part of
the fluid to another
• Hot material=less dense = rises
• Cooler material=more dense= sinks
• Examples: Hot water circulating in a pot on the
stove. Warm air circulating in a room.
Convection in Earth’s
Mantle
• Magma is heated by the core, rises to the crust,
cools, then again sinks to be reheated
• This causes a Convection Current to form in the
upper mantle as shown in the diagram below
CHAPTER 1; SECTION 3:
The Theory Continental Drift
• all continents were
once joined
together in one
single landmass
scientists called:
PANGEA
“Continental Drift”
Evidence For Continental Drift
Landforms
The continents fit
together like
a puzzle
Fossils
Climate
The same fossils
found on several
different continents
Tropical fossils were
found in arctic areas
Mountain ranges
are the same on
Different continents
The same rocks and
minerals are found
at edges of continents
Continents “Drifted” to their current
locations….
CHAPTER 1; SECT. 4:
Sea-Floor Spreading: 1
• The ocean floors are not smooth and
featureless as once believed
• Scientist now know that the ocean floor
has a huge mountain range that encircles
the globe called the MID-OCEAN RIDGE
SYSTEM
Sea-Floor Spreading: 2
-The Process– molten material rises from the mantle and
erupts
– The lava creates new rock at the ridge and
pushes old rock to both sides of the ridge
– Old Rock is destroyed (remelted) at trenches
– This process is called SEA-FLOOR
SPREADING
Sea-Floor Spreading: 3
-diagram-
Sea-Floor Spreading: 5
-Evidence to support it• Volcanic activity has been observed at the
ridge system
• Reversal of magnetic polarity are locked in
rocks on either side of the ridge system at
equal distances.
• Drill samples from the ocean floor are the
same age at equal distances from the
ridge system
Subduction at Deep-Ocean
Trenches
• Deep ocean trenches occur where ocean crust
is thrust underneath continental crust
• Subduction occurs where dense ocean crust is
pushed under less-dense continental crust to be
re-melted in the mantle
• This process occurs over tens of millions of
years
• This process allows new crust to be created at
the ridge systems and old crust to be re-melted;
keeping the Earth the same size
CHAPTER 1; SECTION 5:
The Theory of Plate Tectonics
• Explains:
–Formation of Earth’s Crust
–Movement of Earth’s Crust
–Subduction (destruction) of
Earth’s Crust
Plate Boundaries
• Edges of crustal plates
• Transform Boundary:
– Plates slip past each other in opposite directions (side
to side) Ex: San Andreas Fault
• Divergent Boundary:
– Plates are moving away from each other
– Forms Rift Valleys, mid-ocean ridge
• Convergent Boundary:
– Plates move toward each other and collide
– Forms trenches and rift valleys
Earth’s Plate Boundaries
Prentice Hall, 2000
CHAPTER 2: SECT. 1:
EARTHQUAKES
• EARTHQUAKE:
–A VIOLENT SHAKING OR
TREMBLING OF THE EARTH’S
CRUST THAT RESULTS FROM
MOVEMENT OF ROCK BENEATH
THE EARTH’S SURFACE
Types of Stress in the Crust:
-Shearing Stress• Stress: a force that can cause rock to
change it’s shape or volume
• Shearing Stress: pushes rock in two
opposite, horizontal directions
• Example: San Andreas Fault in California
– One plate moves South and the other one
moves North
Types of Stress in the Crust:
-Tensional• A force that pulls on the crust, stretching
rock so that it becomes thinner in the
middle.
• This occurs when two plates move apart
• Example: North East African Rift Zone
Types of Stress in the Crust:
-Compressional• Stress that squeezes rock until it folds or
breaks
• This occurs when one plate collides with
another
• Example: India and Eurasia; the
Himalayan Mountains are continuing to
grow due to compressional stresses
Faults
• Breaks in the
Earth’s crust
where
movement
occurs
• Usually occur
along plate
boundaries
Three Types of Faults
• Strike-slip Faults:
– Occur along transform boundaries; shearing
stresses
• Normal Faults:
– Occur along divergent boundaries; tensional
stresses
• Reverse Faults:
– Occur along convergent boundaries;
compressional stresses
Mountain Building
• Over millions of year, stresses can turn flat
land surfaces into towering mountains
Mountains from Folding
• Compressional stresses cause rocks to
bend upward or fold
• These folds can create alternating hills
(anticlines) and valleys (synclines)
Mountains from Faults
• Faults can cause areas to be uplifted
thousands of feet
• Fault-Block Mountains:
– Areas where paired normal faults uplift blocks
of rock forming mountains
– Ex: plateaus
Chapter 2: Sect. 2:
Measuring Earthquakes
• Earthquake Focus:
– The location within the Earth where rocks break
releasing earthquake energy
• Earthquake Epicenter:
– The point on the Earth’s surface directly above the
Focus; greatest damage here
• Seismic Waves:
– Three types of shock waves the are emitted from the
focus of an earthquake; used for study
Types of Seismic Waves
• Primary Waves (P-waves):
– First waves to arrive at a seismograph; compression
and expansion; travel through solids and liquids.
• Secondary Waves (S-waves):
– Second waves to be recorded; move the ground up
and down; back and forth
– Travel through solids only
• Surface Waves:
– Very slow; cause severe ground movement; most
damaging form of seismic waves
Detecting Seismic Waves
• Seismograph:
– Device that records ground movements
causes by seismic waves
From Prentice Hall 2000
Rating Earthquake Strength
• Richter Scale
– Rating earthquake
size using a Richter
Seismograph
– Works well for small,
local earthquakes
– Most widely used
method for public
reporting
– Scale of 1 - 10
• Moment Magnitude
Scale
– Used most often by
geologists
– Works for all
earthquakes
– Takes amount of
movement and the
intensity into account
– Much more accurate
Locating an Epicenter
• Collect P and S-wave data from three
seismic monitoring stations
• Calculate the difference in arrival times
between P and S-waves
• Determine the distance to the epicenter
• Draw circles around all three stations with
radii proportional to the distance
• They will intersect at the epicenter!
Earthquake Hazards
• Liquefaction:
– Ground shaking is amplified by loose soil;
buildings sink
• Aftershocks:
– Smaller quakes that occur after a larger one
• Tsunamis:
– Tidal waves that occur when earthquakes
occur under the ocean
Making Buildings Safer
• Choice of building location:
– Locate buildings on shallow slopes, and on
solid ground; bedrock is best
• Base-isolated building:
– A means of building where the foundation of a
building is separated from the rest of the
building by large springs or shock absorbers
– This allows the ground to move but the
building to remain stationary
Inside Earth Chapter 3
Volcanoes
Chapter 3: Sect 1:
What is a Volcano?
• A weak spot in the
crust where molten
material, magma,
comes to the surface
• Magma:
underground liquid
rock
• Lava: liquid rock at
the Earth’s surface
Where are volcanoes
found?
• Ring of Fire:
– A geographic region that rings the Pacific
Ocean
– Many volcanoes occur due to the many plate
boundaries that exist in this region
– Plate boundaries provide a weak spot in the
crust that is necessary for volcano formation
Hot Spot Volcanoes
• A special volcano that is not located on a plate
boundary, but in the center of a plate
• Magma melts through the Earth’s crust to spill
out onto the Earth’s surface
• May be causes by a super-heated plume of
magma (scientists are not sure)
• Hawaii
Chapter 3: Sect 2
Volcanic Activity
What makes a Volcano Erupt?
• Magma rises toward the Crust because it
is hot and less dense than the solid rock
around it, however, it gets trapped under
the crust
• Gases dissolved in the magma build up
• Eventually, the gas must escape; and an
eruption occurs
• The escaping gas pushes the magma
out
Types of Eruptions:
Quite Eruptions
• Quiet Eruptions occur with a very fluid, low
silica, low gas magma
• Example: Mt. Kilauea, Hawaii
• Lava slowly oozes out of the volcanic vent
Types of Eruptions:
Explosive Eruptions
• Explosive eruptions occur with a more
viscous (thicker), higher silica, high gas
magma
• Example: Mt. St. Helens, Washington; May
18, 1980
• Gas cannot escape the thick lava so it
builds up and eventually explodes violently
Mt. St. Helens after 1980 eruption
Other Volcanic Activity
• Hot Springs
Homework
Page 102; 1-4
Chapter 4: Sect. 1
Properties of Minerals
• Mineral:
– A naturally occurring, inorganic, solid,
which a definite crystal structure, and a
definite chemical composition
Identifying Minerals
• Scientists use a mineral’s
characteristics to determine its
identity
• However, they never rely on just one
characteristic because different
minerals may have several
characteristics in common
Identifying Characteristics
• Hardness:
– The tendency of a mineral to be scratched
– Mohs Hardness scale:1(softest) – 10(hardest)
• Color:
– Easily observed but not reliable for
identification; many minerals are the same
color
• Streak:
– Color of a mineral’s powder; very useful
Identifying Characteristics Con’t
• Luster:
– How a mineral reflects light; metallic,
nonmetallic, etc.
• Density:
– Each mineral has a characteristic density
– Very useful for mineral identification
• Crystal Shape:
– Each mineral fits into a one of six crystal
families; useful for classification
Crystal Shapes of Minerals
Identifying Characteristics Con’t
• Cleavage and Fracture:
– How a mineral breaks
– Cleavage is breaking along flat surfaces
– Fracture is breaking randomly
• Special Properties:
– Some minerals have unique characteristics
– Fluorescence: glowing under UV light
– Magnetism, radioactivity, etc.
Chapter 4: Sect. 2
How do minerals form?
• Crystallization from magma:
– Molten magma cools, minerals slowly harden and
settle out
– Ex: feldspars
• Crystallization from water:
– Hot groundwater cools as it travels through the
ground
– Minerals crystallize and adhere to surrounding rock
as the groundwater passes
– Ex: quartz
Chapter 5: Rocks
• Rocks are a combination of 1 or more
minerals
GRANITE
SANDSTONE
Chapter 5: Sect. 1
Classification of Rocks
• Geologists base rock classification on two
things:
– Texture: the size, shape, pattern, or lack of
the individual grains in a rock
– Mineral Composition: the actual mineralogy
of the rock
This helps to determine if the rock is Igneous,
Sedimentary, or Metamorphic
Chapter 5: Sect. 2:
Types of Rocks: Igneous rocks
• Igneous means “born of fire”
• Extrusive igneous rocks:
– Formed from lava at Earth’s surface
– Cool very quickly; fine grained or no grains
– Ex: basalt, obsidian
• Intrusive igneous rocks:
– Form from magma deep underground
– Cool very slowly; coarse grained
– Ex: granite, gabbros
Chapter 5: Sect. 3
Types of Rocks: Sedimentary rocks
• Form from compaction and cementation of
sediments
• 1. sediment is deposited, 2. compacted, 3.
cemented, 4. rock
• Clastic Rocks: made up of parts of other
rocks
• Only rocks with fossils
• Ex: shale, sandstone, conglomerate
Chemical Sedimentary Rocks
• Sedimentary rocks that have crystallized
out of a solution
• Halite (rock salt), Limestone, gypsum
• Form when bodies of water evaporate
over long periods of time
• Great Salt Lake, Utah: this occurs here
today
Chapter 5: Sect. 5
Types of Rocks: Metamorphic
• Igneous or sedimentary rocks that are
heated and squeezed
• The minerals are rearranged but not
melted
• Foliated texture:
– Minerals that are layered or banded in a
metamorphic rock
– Ex: gneiss or schist
Granitegneissschist
Chapter 5: Sect. 6
The Rock Cycle
• Due to weathering, erosion, and
deposition, rocks at the Earth’s surface are
continually being created and destroyed
• The Rock Cycle:
– The processes on and inside Earth that
change rock from one type to another
– Ex: Granite(igneous) weathering/deposition
 sandstone (sedimentary) heat/pressure
 quartzite (metamorphic)
The Rock Cycle
Prentice Hall, 2000