Unit 4 The Restless Earth Part II Lessons 4, 5 & 6 The Big Idea: The movement of tectonic plates accounts for important features of Earth’s surface and.

Unit 4 The Restless Earth Part II Lessons 4, 5 & 6

The Big Idea: The movement of tectonic plates accounts for important features of Earth’s surface and for major geologic events.

http://wondrouspics.com/volcano-photos/

Magma Magic

Volcano- any place where gas, ash, or melted rock come out of the ground• Magma -melted rock is less

dense than solid rock, so it rises to the surface.

• Lava - magma that has reached Earth’s surface. Lava and ash erupt from a vent, or an opening of a volcano.

Unit 4 Lesson 4 Volcanoes

Volcanic Flow• Viscosity-

resistance to flow; shape and explosiveness of a volcano depend on the lava’s viscosity.

• Pyroclastic material- hot ash and bits of rock, may also be ejected into the atmosphere.

http://www.zeitnews.org/node/3350

http://www.studyblue.com/notes/note/n/how-the-earth-works-final/deck/1690726

Volcanic Landforms1. Shield volcanoes -

broad bases and gently sloping sides. • They are the result of mild

eruptions.

2. Cinder cones -small volcanoes with steep slopes. • They form from ash and

pieces of solidified lava that fall around a small vent.

Unit 4 Lesson 4 Volcanoes

3. Composite volcanoes- built

from alternating layers of hardened lava flows & pyroclastic material.

They generally develop into large, steep mountains. Have violent eruptions

4. Lava plateau-fissure eruptions produce flattened layer of cooled lava

Unit 4 Lesson 4 Volcanoes Volcanic Landforms continued

5. Caldera – magma chamber empties, the roof of the chamber can collapse, leaving a large basin-shaped depression

Magma chamber-expanded area of magma

Unit 4 Lesson 4 Volcanoes Volcanic Landforms continued

Eruption! Where do Volcanoes come from?

Tectonic plates -giant sections of lithosphere on Earth’s surface. Volcanoes can form at plate boundaries or within the middle of a plate.

1. Divergent boundaries-creates fissure eruptions & shield volcanoes, crust stretches & gets thinner. Most occur on ocean floor, creating undersea volcanoes, long underwater mtn range known as mid-ocean ridge. On land the crust stretches until a rift valley is formed.

Unit 4 Lesson 4 Volcanoes

http://ajs-geo-blog.blogspot.com/2012/03/rift-valley.html

2. Convergent boundaries- composite volcanoes or calderas can occur. Magma has high concentration of fluids, which form gas bubbles

3. Hot spots-far from any plate boundary, shield volcanoes, fissure eruptions & cinder cones can occur.

4. Ring of Fire –numerous explosive volcanoes that form on convergent boundaries surrounding the Pacific Ocean.

Unit 4 Lesson 4 Volcanoes

http://volcanoworld.wordpress.com/2011/12/12/what-is-a-hot-spot-and-what-is-a-mantle-plume/

http://www.eclp.com.na/demo/geography/mod1page24.html

Let’s Focus• Earthquakes are ground movements that occur when blocks of rock in Earth move suddenly and release energy.

The energy is releasedas seismic waves thatcause the ground to move.

Unit 4 Lesson 5 Earthquakes

http://www.fhmindia.com/tag/earthquakes/

What Causes Earthquakes?

1.Faults -release of energy that accompanies the movement of rock along a fault causes an earthquake.

2.Deformation-process by which the rock becomes deformed and changes shape caused by stress

As the stress on rock increases, the energy stored in it increases.When the stress is released, the rock may return to its original shape.When rock returns to nearly the same shape after the stress is removed, its called elastic deformation.

3.Elastic rebound- return of rock to its original shape after elastic deformation

Unit 4 Lesson 5 Earthquakes

What is an Earthquake?

Focus-place w/in Earth along a fault where the first motion of an earthquake occurs. Seismic waves flow outward in all directions

Epicenter- place on Earth’s surface directly above the focus

Unit 4 Lesson 5 Earthquakes http://pmikecolumbus.wordpress.com/2012/02/29/ripples-in-the-water/

http://geomaps.wr.usgs.gov/parks/deform/geqepifoc1.html

Where do Earthquakes happen?

Divergent boundaries- tension stress causes normal faults to form. Earthquakes tend to be shallow because the crust is thin.

Convergent boundaries- rock is squeezed, & the stress is called compression. Reverse faults are formed, and earthquakes can be strong and deep.

Transform boundaries- shear stress pushes tectonic plates in opposite directions. Earthquakes tend to be relatively shallow.

Unit 4 Lesson 5 Earthquakes

Shake, Rattle & RollSeismic waves -

vibrations that cause different types of ground motion. Their speed depends on what they travel through

1. Surface waves- travel along Earth’s surface

Unit 4 Lesson 6 Measuring Earthquake Waves

Seismic Waves continued2. Body waves- travel through Earth’s

interior A. P waves – pressure waves or primary

waves are the fastest B. S waves- shear waves secondary,

move side to side

Unit 4 Lesson 6 Measuring Earthquake Waves

Wave Action!Seismogram -

tracing of earthquake motion. It also records the arrival times of seismic waves at a seismometer station.

Page 259 to see triangulation.

http://www.qrg.northwestern.edu/projects/vss/docs/navigation/1-what-is-triangulation.html

Unit 4 Lesson 6 Measuring Earthquake Waves

Earthquake Measurement

Magnitude- measure of the energy released by an earthquake, larger magnitude = stronger earthquakeRichter scale-measures ground

motion from an earthquake to find the strength

Moment Magnitude scale-more accurate for large earthquakes, based on area of moving fault, avg distance the fault moves & rigidity of rocks in the fault.

http://www.panorama.am/en/society/2012/10/08/mes-az/Unit 4 Lesson 6 Measuring Earthquake Waves

Did you feel that? Intensity-effects of an earthquake and how the

earthquake is felt by peopleEffects of an Earthquake

1. Magnitude 2. Local geology3. Distance from the epicenter4. Type of construction used

Unit 4 Lesson 6 Measuring Earthquake Waves

http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/earthquake_effects.html

http://www.ga.gov.au/ausgeonews/ausgeonews200606/sediments.jsp