Transcript EarthquakesandVolcan..

Earthquakes
and
Volcanoes
Earthquakes
Earthquake – is the shaking and
trembling that results from the sudden
movement of part of the Earth’s crust.
Tsunamis – A giant sea wave produced
by an earthquake.
Seismic Waves
Focus – The point beneath the Earth’s
surface where the rocks break and
move, the underground origin of the
earthquake.
Epicenter – The point directly above
the focus, on the earth’s surface where
the origin of an earthquake is above
ground.
Seismic waves – earthquake waves. *Three
types.
1. Primary waves (P-waves) –
arrive at a given point before any other type
of seismic wave. Will pass through solid,
liquid and gas.(fastest of the three)
2. Secondary Waves (S-waves) –
arrive at a given point after the P wave.
(second fastest) Will only travel thru solids.
Will NOT pass through liquids and gases thus
creating a shadow zone.
3. Surface waves (L-waves) –
slowest moving seismic waves.
Arrives last.
Seismograph – is an instrument that detects
and measures seismic waves.
Seismogram – is the record of waves.
(paper record)
Seismologists – scientists who study
earthquakes.
Richter scale – calculation of the strength
or magnitude of an earthquake.
For every 1 point rise 30 times the
energy is released.
Magnitude - Height of a line traced on a
seismogram.
Liquefaction – Shaking up of wet soil making it
unstable. This causes surface object to sink.
Earthquake preparedness – Tie down heavy objects,
take objects off of high shelves. Build on an
earthquake proof foundation. Have a plan and
emergency items.
Volcanoes
Volcano – the place in the Earth’s surface
through which magma and other
materials reach the surface.
Magma – rock that exists as a hot liquid
deep within the earth.
Lava – is magma that reaches the Earth’s
surface.
Vent – an opening from which lava
erupts.
Crater – Steep walled depression around
a volcano’s vent.
Hot Spot – Hot rock that is a result of
unusually hot areas in the mantle and core
where volcanoes form on the Earth’s
surface. Hawaii is the result of a hot spot.
Lava flows
• Basaltic – Is lava that contains a lot of
water and rich in iron and magnesium.
Thin and quiet eruptions.
• Granitic - this lava contains very little
water and is rich in silicon and aluminum.
Thick heavy lava causing gases to trap
underneath producing large violent
eruptions.
Andesitic - is a combination of both granitic
and basaltic lava flows (quieter than granitic but
more violent than basaltic).
Gas filled lava – This lava cools to form hole
filled rock that has the appearance of a sponge
or loaf of bread. This rock type is typically light
in weight. Pumice and scoria are examples of
this type of igneous rock.
Tephra – bits of rock or solidified lava dropped from
the air.
Volcanic Dust – Is fragments of rock that are blown
into the air during a volcanic eruption. (very small
particles)
Volcanic Ash – Is particles blown into the air from a
volcano that are bigger than volcanic dust yet smaller
than anything else.
• Volcanic Bombs – Are large rock particles that are
blown out during a volcanic eruption.
• Volcanic cinders – are smaller volcanic bombs.
• Cinder cone volcano – Volcanoes made mostly of
cinders and other rock particles that have been
blown into the air. Narrow bases with steep sides
due to loosely arranged cinder type eruptions.
Shield volcano – Volcanoes composed of quiet lava
flows. Gently sloping sides with very wide base.
Composite Volcanoes – are made of alternating layers
of rock particles and lava. Violent eruptions followed
by quiet lava flows are the reasoning for the
alternating layers.
Caldera – A roughly circular, steep-sided pit at the top
of a volcanic cone whose diameter is at least three
times its depth.
Dike –
Batholith –
Sill -
Dormant – (sleeping) has erupted but not in modern
time.
Extinct – Not known to have erupted in recorded
time. Usually weathered down to base.
Active – well, it is active in modern time.
ZONES
Ring of fire – is the zone of active earthquakes and
volcanoes due to very active tectonic plate movement.
Mid-Atlantic ridge – chain of ridges caused by sea
floor spreading.