Earthquakes And Volcanoes Chapter 4 Lesson 2 Earthquakes And Volcanoes

Earthquakes

Earthquakes Earthquake – sudden movement of Earth’s crust The actual place underground where the rocks break producing vibrations is called the focus The place on the surface directly above the focus is called the epicenter

Normal Fault http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en

Reverse Fault http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en

Strike-Slip Fault http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en

San Andreas Fault

Seismic Waves Originate at the focus and travel outward in all directions Magnitude – the measure of the amount of energy released by an earthquake Aftershocks: Are adjustments in the crust after in earthquake

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

Volcanoes 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 Built from layers of lava Non-explosive eruptions Not very steep, but can be big

Types of Volcanoes Cinder Cone Volcano Built from pyroclastic material Moderately explosive, short eruptions Small in size, steep slopes

Types of Volcanoes Composite Volcanoes Most common type Explosive eruptions and lava flow Built from pyroclastic material AND lava

Mt. St. Helen before the explosive eruption

Volcanoes

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 Hotspots