Earthquakes and volcanoes

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.

Lava flows

BasalticIs lava that contains a lot of water and rich in iron and magnesium. Poor Silica content. 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).

Tephra

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 cinders – are smaller volcanic bombs.

Volcanic Bombs – Are large rock particles that are blown out during a volcanic eruption.

Cinder cone volcano – Volcanoes make 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. Granitic lava

Shield volcano – Volcanoes composed of quiet lava flows. Gently sloping sides with a very wide base. Basaltic lava

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. Andesitic lava flows

Batholiths - giant pools of magma that cool seperate from the main magma chamber of a volcano that solidfy and can become exposed to the surface due to erosion.

Sill - magma that penitrates cracks in rock that runs paralell with the rock.

Dike - magma that penitrates cracks in rock that cuts across existing rock layers.

earth_crust

Caldera – A roughly circular, steep-sided pit at the top of a volcanic cone whose diameter is at least three time its depth. Dormant – (sleeping) has erupted but not in modern time.

Extinct – Not known to have erupted in recorded time. Usually weathered down to base.

Active – active in modern time.

ZONES

Ring of fire – is the zone of active earthquakes and volcanoes do to very active tectonic plate movement.

Mid-Atlantic ridge – chain of ridges caused by sea floor spreading.

Mid Atlantic Ridge

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 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. And the most destructive.

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 - The 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. Read this section in the book!!

Earthquakes

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 above ground.

epicenter


Seismic waves – earthquake waves. *Three types.

  1. Primary waves (P-waves) – arrive at a given point before any other type of seismic wave. (fastestof the three)
  2. p-waves













  3. Secondary Waves (S-waves) – arrive at a given point after the P wave. (second fastest
  4. s-waves
















  5. Surface waves (L-waves) – slowest moving seismic waves. Arrives last. Most destructive!
Earthquake Surface Waves - the most deadly
   
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