Chapter 4 Lesson 2 Earthquakes And Volcanoes
Jan 07, 2016
Chapter 4Lesson 2
EarthquakesAnd
Volcanoes
o Earthquake – sudden movement of Earth’s crust
o The actual place underground where the rocks break producing vibrations is called the focusfocus
o The place on the surface directly above the focus is called the epicenterepicenter
Earthquakes
http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en
http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en
http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en
San Andreas Fault
Originate at the focus and travel outward in all directions
Magnitude – the measure of the amount of energy released by an earthquake
AftershocksAftershocks: Are adjustments in the crust after in earthquake
Seismic Waves
Volcano – opening in the Earth’s crust• Eruption –
outpouring of melted rock, ash, and gases
• Lava – magma that reaches the Earth’s surface
• Crater – a • depression
around a vent
Ring of Fire The ring around the Pacific Ocean that has most of the world’s
volcanoes
VolcanoesVolcanoes
Quiet lava flows
• Dike – magma that hardens in a vertical crack
• Sill – magma that hardens between horizontal layers of earth
• Laccolith – magma in a sill that pushes upward
• Batholith – large, underground magma formation
Types of Volcanoes
• Shield Volcano
a) Built from layers of lava
b) Non-explosive eruptions
c) Not very steep, but can be big
Types of Volcanoes
• Cinder Cone Volcano
a) Built from pyroclastic material
b) Moderately explosive, short eruptions
c) Small in size, steep slopes
Types of Volcanoes
• Composite Volcanoes
a) Most common type
b) Explosive eruptions and lava flow
c) Built from pyroclastic material AND lava
Mt. St. Helen before the explosive eruption
VolcanoesVolcanoes
Mt. St. Helen after the eruption
• Island chain – line of volcanic mountains
• Hot spot – stationary pool of magma
• Island arc – volcanic islands that are made my subducting ocean floor plates
Mid-Plate HotspotsMid-Plate Hotspots