Transcript 1-10 levels at which an earthquake

And
Earthquakes
• Shaking and trembling of the
earth’s crust.
• The waves travel in all
directions
• More than 1,000,000 occur a
year or one every 30 seconds
• Faulting is the most common
cause
• Earthquakes continue until all
the energy is used up
• TSUNAMIS- earthquake on
the ocean floor: causing waves
to become greater than 20
meters high
Seismic Waves
FOCUS
underground point of origin
EPICENTER-
above ground origin; most
violent shaking occurs at the
epicenter
Types of Waves
• Three main types
of seismic waves
are: P waves, S
waves and Surface
Waves
P Waves
• Primary waves
• Arrive first at the
epicenter
• Can travel
through solids,
liquids, and gases
• They are pushpull waves
S Waves
• Secondary waves
• Can travel through
solids, but NOT
through liquids and
gases
• Move in up-down
motion
Surface Waves
• Slowest moving
seismic waves
• Travel on top of
Earth’s surface
• Cause most of
damage to Earth,
because they bend
and twist the surface
Normal Fault
• Tension force
• Stretching or pulling
force
• Occurs at divergent
boundary
• Blocks of crust that
are pulled away from
each other slide along
normal faults
Reverse Fault
• Compression force
• Force pushing
something together
• Occurs at a
convergent boundary
• Blocks of crust that
are pushed together
slide along Reverse
Faults
• Strike Slip Force
• Shear force
• Force that operates
against a body from
different sides
• Occurs at a transform
boundary
• Blocks of crust slide
horizontally past each
other.
John Milne- 1893
Seismograph
measures and detects seismic
waves
Seismogram
Paper record of waves
Seismologist
scientist who study earthquakes
Richter Scale
a scale that allows scientists to
determine earthquake strength
based on many readings
1-10 levels at which an earthquake
is measured on amount of damage
caused; Above a 6 is very
destructive
VOLCANOES
Volcano
place on Earth’s surface
that allows magma and
other material to erupt
Magma
found beneath the
Earth’s surface, it is
liquid rock
Lava
magma that reaches
the Earth’s surface
Volcanic Fragments
Volcanic Dust
• less that 0.25 mm in
diameter (flour)
Volcanic Ash
• more than 0.25 less
than 5 mm (rice)
Volcanic Bombs
• few cm to several
meters
Cinder
• volcanic bombs the
size of golf balls
Types of Volcanoes
Cinder Cones
made of mostly of
cinders; formed from
explosive eruptions
Shield
of quiet lava flows,
world’s largest
volcanoes
Composite
made up of alternating
layers of rock particles;
explosive eruptions,
then quiet lava flows
Composite Volcano
Shield Volcano
Cinder Cone
Volcano
Hot Spot Volcanoes- Hawaiian Islands
Types of Lava
Viscosity
• how lava flows
• High viscosity is stiff
• Low viscosity is more
fluid
Aa Lava
• Pours out quickly and
forms a brittle crust,
crust torn into jagged
pieces as molten lava
continues to flow
underneath
Pahoehoe
• Lava flows slowly, like
wax dripping from a
candle. Glassy
surface with rounded
wrinkles
Pillow Lava
• Forms when lava
erupts underwater.
Forms round lumps
(often shape of
pillows)
Blocky Lava
• Cool, stiff lava that
does not travel far
from the erupting
vent. Oozes and
forms piles of sharpedged chunks
Volcanic Terminology
Crater
Caldera
• Funnel shaped pit, or
depression at the top
of a volcano
• When a crater
becomes too large, it
collapses: also can
form when the top of
a volcano collapses
or explodes
Dormant
Extinct
Active
• sleeping volcano
• not known to have
erupted in modern
history
• Erupts fairly regularly
Ring of Fire
Water content
• Higher water content
more likely to have
explosive eruption
Benefits of volcanoes
• Despite the dangers, humans do benefit
from volcanoes.
• Rock from lava is used in roads
• Pumice is used for polishing items
• Weathered volcanic ash improves soil
• In some areas, volcanic steam is used for
heat
EXTRA! EXTRA!
• Mount St. Helens is a volcano
in Washington State
• San Andreas Fault in
California
• New Madrid Fault is where we
live