earthquakes and volcanos earth science mr.mckay earthquakes earthquake – the shaking and trembling...
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Earthquakes and
Volcanos
Earth Science
Mr.McKay
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Earthquakes• Earthquake – The shaking and
trembling that results from the sudden movement of part of the Earth’s crust– Pebble in pond– Scientists predict over 1,000,000
earthquakes happen each year– Faulting is most common reason for
Earthquakes• San Andreas Fault
– Fault Video
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Tsunamis• Tsunami- A huge wave
caused by an earthquake on the floor of the ocean– They can travel at speeds
of 700 to 800 MPH– They can reach Heights of
20 meters• The height of a 6 Story
Building• Tsunami Off of Thailand• Trouble in Paradise
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Seismic Waves• Earthquake waves are
known as seismic waves– Focus- The point beneath
the Earth’s surface where rocks break and move
• The focus is the point of origin for the earthquake
– Epicenter- Directly above the focus on the Earth’s surface
• Earthquake waves reach the epicenter first
• Seismic Waves
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Seismic Waves• Primary waves-
– P-waves: Seismic waves that travel the fastest
• They arrive at a given point before any other type of wave
• They travel through– Solids– Liquids– Gases
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Seismic Waves• Primary waves-
– They move through the Earth differently depending on the material they are traveling through
– As they move deeper into the Earth, where it is more dense, they move faster
– They are push-pull waves
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Seismic Waves• Secondary Waves
– S-Waves – Seismic waves that do not travel through the Earth as fast as P-waves do
– S-waves arrive at a given point after P-waves do– S-waves travel through solids but not liquids and
gases
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Seismic Waves
• Surface Waves– L-waves: They are the slowest moving seismic waves
• They arrive at a given point after P and S waves– They start at the epicenter and move along the Earth’s surface– Earth’s surface moves up and down like water waves do– They cause the most damage to the Earth because they bend
and twist the surface
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Seismograph• Seismograph – An
instrument that detects and measures seismic waves– Crude Seismographs
around for hundreds of years
– The first practical was made in 1893 by John Milne
– Consists of • A weight attached to a spring
or wire• A pen attached to the weight
that records the movement of the Earth on a paper, that is wound tightly around a constantly moving drum
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• Seismologists – Scientists who study earthquakes– PSP Seismograph– They can determine the strength of
an earthquake by studying the height of the waves
• They look at a Seismogram• They match the seismogram to a chart
called the Richter Scale– Invented in 1935– The scale is from one to ten, with any
earthquake above 6 being very destructive
Seismograph
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• Formation
• High temperature• High Pressure• Liquid State• Found in pockets called magma
chambers
– Magma constantly moves and works its way through cracks toward the surface by melting the solid rock
Volcanoes
–Magma: Rock deep within the Earth
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• Formation– Lava – Magma that has reached
the Earth’s Surface– The place where magma becomes
lava is called a Volcano– The opening through which lava
erupts is called a vent• Volcanoes can have more than one
vent– Lava will poor from the sides of a
volcano as well as the top
Volcanoes
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• All are not Alike– Some are quiet
• Lava oozes from a vent
– Others are violent• With lava and other material hurled
hundreds of feet in the air• Gases and earth material mix to be seen
from miles away
– The opening through which lava erupts is called a vent
• Volcanoes can have more than one vent– Lava will poor from the sides of a
volcano as well as the top
– Eruption
Eruptions
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• Scientists study the makeup of the lava that spews from the Volcanoes vents to gain knowledge about the interior magma
• Types of Lava– Dark-colored/ Water– Light-colored/ little Water– Chemical composition of both– Large amounts of gases
• Steam and carbon dioxide
Eruptions
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Eruptions• During eruptions many rock fragments are blown
into the air– Smallest = volcanic dust– Medium = volcanic ash– Large = volcanic bombs
• Small volcanic bombs the size of golf balls are called Cinders
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Types ofVolcanoes
• Different types of volcanic eruptions form different types of volcanoes– Cinder Cones - made mostly of cinders and other rock
particles that have been blown into the air• Form from explosive eruptions• Cones are not high• Narrow base & steep sides
– Shield Volcanoes – composed of mostly quiet lava flows
• Gently sloping, domed shaped mountain forms– Composite Volcanoes – Built up of alternating layers
of rock particles and lava• First is a violent eruption• Then a quiet eruption• After many alternating eruptions a cone shape is formed
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Types ofVolcanoes
• At the top of a funnel-shaped pit or depression is a pit– Called Crater
• If it becomes to large it is called a Caldera• Super Eruption• Discovery Channel :: Virtual Super volcano
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• Three Major Zones– Nearly all the way around the edge of the
Pacific Ocean• Called the Ring of Fire
– Near the Mediterranean Sea• Called the Mediterranean Zone
– Third Extends through Iceland to the middle of the Atlantic Ocean
• Mid-Atlantic Ridge – Long ridge of volcanoes
Zones