Daily Science Dec 3 What are the three different types of volcanoes? Give one characteristic of each. What are the 3 different types of magma and how do they differ? Which type of magma causes the most violent eruption? What are plutons? Describe the anatomy of a volcano.

Earthquakes Pg. 59

Stress and strain Most occur when rocks fracture or break deep within Stress exceeds the strength of the rock Three types of stress: ◦Compression ◦Tension ◦shear

Faults Surface along which movement takes place is called fault plane Arrows are used to show direction in diagrams Types of faults ◦Reverse faults-horizontal compression ◦Normal faults- horizontal tension (partially horiz. Partially vert.) ◦Strike-slip faults- horizontal shear (San Andreas Fault)

Types of faults

Earthquake waves Earthquakes caused by movement in faults 3 types of seismic waves (vibrations in earth) ◦Primary waves-rocks will change shape ◦Secondary waves ◦Surface waves-moves in two directions P and S waves travel though Earth’s interior

Instruments used to measure Seismometer-uses a rotating drum and suspended mass connected to a pen Transfers to a seismogram Seismologists have been able to record the times for s and p waves to travel and have constructed travel-time curves P waves arrive first Can use seismic waves to predict the interior of the earth

Seismometer

Measuring and locating earthquakes On the Richter scale each increase in number represents an increase of a factor of 10 in magnitude most seismologists use the moment magnitude scale Can also use the modified Mercalli scale

Locating an earthquake Spot inside the earth where an earthquake occurs is called the focus The spot directly above the focus on the surface is called the epicenter Can use travel-time curves to determine the location of the epicenter Must have data from 3 stations to locate an epicenter Determined by the P-S wave separation Can determine lag-time (time between s and p waves) Most earthquakes occur in seismic belts- narrow areas