Earthquakes
&
Volcanoes
Earthquakes
• Occur mostly at boundaries of
tectonic plates
• Stress of moving plates becomes so
great it breaks rock
•Seismic waves – energy released
from shifting. Produces shaking
• Focus – exact point inside the earth
where the earthquake originates.
• Epicenter – the point on the surface
of the earth directly above the focus.
3 types of waves
1. __P or Primary waves___________________
• Originate at the focus
• move faster than other waves
• they are longitudinal waves
2. _____S – secondary waves________________
• Originate at the focus
• Travel more slowly than P waves
• They are transverse waves
3. __Surface Waves_____
• Move only across the earth’s
surface
• Cause the most destruction
• Generates rolling action at the
earth’s surface
Seismology
• Study of earthquakes.
• Seismograph – instrument that detects
earthquakes.
• 3 seismograph stations are necessary to
locate the epicenter of an earthquake.
Richter Scale – describes the amount of energy an
earthquake has, cannot predict
amount of damage that will occur
Volcanoes
• Any opening in the earth’s crust through
which magma has reached
• Vent – term for opening in the earth
• Lava – magma that has reached the earth’s
surface.
• There are 3 types
Shield Volcanoes
• fluid iron and magnesium rich magma
• mild eruptions which happen many times
• form some of the largest volcanoes
• Examples Mauna Loa, Haleakala
Composite Volcanoes
• Alternating layers of ash, cinder, and
lava
• thick ,lava, rich in silica
• trapped gas causes eruptions to
alternate between lava flows and
explosive activity that produces cinders
and ash
• Examples Mt. Fuji
Cinder Cone • smallest and most abundant
• lava contains large amount of gas. Causes
eruptions with a large amount of ash.
• active for only a short period of time, then
go dormant
• Examples Paricutin