Download Ch 6 Lesson 3 EARTHQUAKES AND vOLCANOES - Gallion-Wiki

Chapter 6 Lesson 3
Earthquakes p. 246
 Earth’s plates bend and break under pressure.
Vocabulary
Fault –a break in the Earth’s crust where
rocks can slide past each other.
Earthquake-The snap and slide of rocks
as energy is released in Earth’s crust.
Focus-The point inside Earth where an
earthquake begins
Epicenter-The point on Earth’s surface
directly above the focus of an earthquake
Fault
 A fault is the term used when rocks break. A fault is
a break in the Earth’s crust where rocks can slide
past each other.
 Most faults form along plate boundaries but can also
form within a plate.
Focus
 The point inside the Earth where the earthquake
begins.
 It can be near the surface or deep within the Earth.
Earthquakes p. 246
 Plates move; pressure builds up.
 Rocks bend and stretch. If they snap, they release
energy suddenly in the form of an earthquake.
Epicenter
 The point on the Earth’s surface directly above the
focus of the earthquake
Earthquake Waves
 P waves-Primary waves Travel through the interior.
 Energy travels away from the focus.
 P waves are the fastest waves and
are the first to be detected.
 They compress and expand the
ground. (like an accordion)
Earthquake Waves
 S waves-Secondary waves Travel through the interior
 These waves travel across
the direction that the P waves
are moving.
 They move up and down and
side to side.
Earthquake Waves
 -Surface waves travel along the Earth’s surface.
 Some shake the ground from side to side.
 Some roll like ocean waves.
 Both of these cause most of the damage done to
buildings that is done by an earthquake.
Measuring Earthquake Strength and
Damage p. 250
 Seismographs measure and record motion caused by
an earthquake’s energy waves.
Measuring Earthquake Strength and
Damage p. 250
Measuring Earthquake Strength and
Damage p. 250
 Seismographs measure and record motion caused by
an earthquake’s energy waves.
 The time between the arrival of the P and the S
waves is recorded. The more time that elapses, the
further away is the epicenter.
Richter Scale
Richter Scale
1935, Charles Richter developed a scale
to measure earthquake strength.
Uses the size of waves recorded on a
seismograph to determine how strong
an earthquake is.
Scale estimates the amount of energy
released by an earthquake.
2.0 is minor
4.0 can be felt but causes little damage.
6.0 or greater can cause major damage.
Moment Magnitude Scale
 Measures the distance rock along the fault moves.
This is used to determine the energy released.
 Numbers are similar to the Richter scale but is
believed to be more accurate.
 Measures earthquake strength.
Mercalli Intensity Scale
 Measures damage caused.
 Uses Roman numerals.
 XII means buildings were completely destroyed.
Tsunami
 When an earthquake happens under the ocean the
sea floor will rise and fall.
 The movement of water can cause a giant wall of
water (May be more than 30m.)
 May cause massive damage to buildings near shore.
Tsunami
Volcanoes
Volcanoes
Some mountains are formed when rocks
at convergent boundaries are deformed
and lifted.
Volcanoes
Some mountains are volcanoes and are
formed when molten rock, or magma is
pushed to the surface and builds up.
Volcanoes
Most volcanoes are along the
boundaries of plates.
Volcanoes
Some form along divergent boundaries
where plates are pulling apart and
magma rises to the surface.
Volcanoes
Some form along convergent
boundaries where oceanic crust is
pushed down.
3 Types of Volcanoes
Shield
Cinder Cone
Composite
Shield Volcano
Shield Volcano
Formed by NON-EXPLOSIVE eruptions
Layer after layer builds up slowly.
Broad, slightly dome shaped
May erupt many times
Shield Volcano
Cinder Cone Volcano
Formed by EXPOLSIVE eruptions, composed
of ash and rock thrown out of vent
Erode quickly
Steep sides
Erupt for a short period of time.
Few are taller than 300m or 1000 ft.
Cinder Cone Volcano
Cinder Cone Volcano
Composite Volcanoes
Formed by a mixture of explosive and
non explosive eruptions
May erupt off and on for many years.
Compostie Volcano
Composite Volcano
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Hawaiian Volcanoes
Hawaiian Volcanoes
These volcanoes are NOT formed at
plate boundaries.
Hawaiian Volcanoes
Sometimes magma occurs at another
area of a plate, called a hot spot.
Hawaiian Volcanoes
The magma pushes up, and if it erupts
above the surface, it can form a volcano.
Hawaiian Volcanoes
As the plates move over the hot spot,
the volcano that was formed stops
erupting and a series of new volcanoes
may form.
Hawaiian Volcanoes
If the hot spot lies under the oceanic
crust, the series of volcanoes may
become a chain of islands.
Hawaiian Volcanoes
The youngest island, Hawai’i, has three
active volcanoes.
They have been constantly erupting
since 1983.
Hawai’i
Oahu
Kauai