Transcript Earth Processes

Earth Processes
Geology =
the scientific study
of our planet Earth
• How would you
describe the
Earth’s Surface?
• How did the
surface get this
way?
Plate Tectonics
• The lithosphere is broken into 20 sections
called PLATES
• Each PLATE is a huge slab of rock that
includes the crust
• Fit together like a jigsaw puzzle
• Page 218
• Plates float on layer of partly melted rock
• Can move 2cm – 15cm/yr
Why do they move??
• CONVECTION CURRENTS cause plates
to move
• Convection currents cause hot matter to
rise while cool matter sinks
• MAGMA moves up and spreads out
sideways in a circular pattern
• Magma carries the plates with it
To Review…
•
The sections of the lithosphere are called
A. Crusts
B. Plates
C. Puzzle pieces
•
Convection currents cause
A.
B.
C.
D.
E.
Cool magma to rise and hot magma to sink
Hot magma to rise and cool magma to sink
The movement of the Earth’s plates
Both B & C
Both A & C
Plate Tectonics
• Changes will occur in the Earth’s
crust where 2 plates meet
• A FAULT is a crack in the Earth’s
crust along which rock moves
• Each plate boundary is a huge fault
(226)
Faults
1. Fracture boundary = two plates sliding
past each other
• San Andreas Fault
Faults
2. Spreading
boundary –
plate moving
away from each
other and new
crust added to
the surface
• Great Rift
Valley
Faults
3. Colliding
boundary =
plates move
toward each
other =
mountains
• Himalayas
To Review
•
•
•
At which type of fault would the plates
move into each other and cause
mountains to form?
At which type of fault would plates slide
past one another?
At which type of fault would plates move
away from each other?
A. Fracture boundary
B. Spreading boundary
C. Colliding boundary
Writing for Science
• Write a letter to a 2nd grader telling them
what you learned about Plate Tectonics
today
• Must include:
– What the earth’s crust is made of
– What causes the plates to move
– How much the plates move in a year
– What a fault is
Earthquakes
• Plates will get caught on each other
• Pressure builds until rock breaks
and lurches forward
• An earthquake is a sudden shaking
or vibrating of the Earth’s crust
• Most occur along plate boundaries
(228)
• Built up energy is released
Earthquakes
• The focus is where the first rock
moves
• Waves move out that make the
ground shake = ground rolling,
shaking or lifting
• The Epicenter is directly above on
the Earth’s surface
Earthquakes
•
Types of Seismic Waves –
– S-waves (secondary)
• Make rock move up and down and side to
side, deep underground
– P-waves (primary)
• Deep below the ground they stretch and
squeeze the rock particles
– L-waves (long)
• Travel along the surface
• Causes the most damage
Earthquakes
•
•
Seismograph is the instrument records the
seismic waves of energy that radiate from the
focus of an earthquake
Richter Scale is a series of numbers used to
describe the total amount of energy released,
or magnitude of an earthquake (1930)
–
•
Each increment is 10x stronger
Tsunamis are caused by earthquakes under
the sea that generate a powerful wave that
travels to the surface
To Review
•
Which type of wave moves along the surface of
the earth during an earthquake?
A. S-waves
B. L-waves
C. P-waves
• The first rock moves at the ________.
A. Epicenter
B. Focus
To Review
• What is the name of the instrument that
records the seismic wave that occur
during an earthquake?
A. Richter Scale
B. Seismograph
C. Tiltmeter
Volcanoes
•
•
•
•
•
An opening in the Earth’s surface
through which magma rises
Most occur at the plate boundaries and
hot spots
Many on the ocean floor
Try to predict to save lives
Tiltmeter – detects change in slope of
volcano = magma might be moving
Volcanoes
CRATER
ASH & CINDERS
LAVA
VENT
MAGMA
Volcanoes
•
Eruptions depend on
– Water vapor and gases in magma
• If escaping easily = quiet eruptions
• Under pressure = explosive eruption
– Lava
• Vicious lava (thick and sticky) has gas
that escapes with force and throws ash
high in the air
• Non-viscous lava is thin and runny and
lava will flow from the vent
Volcanoes
•
At a subduction/colliding boundary
1. Sinking crust melts into magma as it enters
the mantle
2. Hot magma is less dense than solid rock
3. Magma rises through openings in crust
4. Gases in magma cause pressure to build
5. When pressure is great enough – magma
breaks through surface as LAVA
Volcano Types
Composite = formed from
alternating eruptions of
cinders /ash & lava
• Above subduction
zones
• Mt. Saint Helen’s
Volcanoes
•
At a Hot Spot
1. Areas in mantle hotter than others
2. Magma has melted through the crust
3. This will form several volcanoes that
will turn in to islands (Hawaii)
Volcano Types
Shield = quiet eruptions that spread
out in flat layers
• Forms a broad volcano with gently
sloping sides
• “New real estate”
• Hawaiian Islands
Volcano Types
Cinder cone = steep sided volcano
• Form from explosive eruption of lava,
ash and cinders
• Steep with small
crater
• Form rapidly
• Paricutin
To Review
•
Quiet volcanic eruptions result from
A. Water vapor and gases under tremendous
pressure
B. Water vapor and gases escaping easily
To Review
•
The type of volcanoes that are created at
subduction zones are
A. Cinder
B. Composite
C. Shield
To Review
•
The type of volcanoes that are created at
areas where the mantle is hotter than the
crust are
A. Cinder
B. Composite
C. Shield
To Review
•
When magma reaches the surface of a
volcano it is called
A.
B.
C.
D.
A crater
A vent
Cinder
Lava
Soil Formation
• Why is soil important?
• Soil = mixture of weathered rock and
decayed plant and animal (organic) matter
formed over a long time
• Also includes mineral fragments, water and
air
• Weathering = process of rock breaking into
smaller and smaller fragments
• Humus = dark colored organic matter made
of pieces of decaying plants and animals
• Worms mix the humus with rock fragments
Soil Profile
• Topsoil –
– Dark
– Contains humus
– Worms
• Subsoil–
– Little or no humus
– Some plant roots
– Minerals washed down
from topsoil
• Bedrock –
– Weathered rock
– No humus
– Beginning the process of
becoming soil
Rock Cycle