Warm Up 09/26/2016 What are the three types of boundaries and explain the motion that occurs at each? What is produced at a Transform Boundary? What happens at a Subduction Zone? What does Plate Tectonics Explain? What layer of the Earth contains convection currents?

Earthquakes 2.1.1 Describe the anatomy of an earthquake

Essential Question How can I locate the epicenter of an earthquake? Video http://studyjams.scholastic.com/studyjams/jams/scie nce/rocks-minerals-landforms/earthquakes.htm

What is an earthquake? An earthquake is a shaking of the ground caused by the sudden breaking and movement of large sections (tectonic plates) of the earth's rocky outermost crust. Most earthquakes occur along the fault lines when the plates slide past each other or collide against each other. More than 95% occur along PLATE BOUNDARIES

The main cause of an earthquakes is the Elastic rebound Theory - The elastic rebound theory is an explanation for how energy is spread during earthquakes.  Rocks become strained and shift. - Most earthquakes are the result of the sudden elastic rebound of previously stored energy.

Ring of Fire 80% of the world’s earthquakes occur in a ring that borders the pacific ocean This ring is called “the Ring of Fire”

This photo shows the Mission District of San Francisco burning after the 1906 earthquake. The greatest damage in earthquakes is often not from the ground shaking but from the effects of that shaking.

1906 San Francisco Earthquake Gas mains break, fires shaken out of furnaces. Water mains break, cannot fight fires. Debris in streets, Fire department cannot reach fires.

Anatomy of an Earthquake

Focus Release of energy starts here... An Earthquake starts at a location inside the Earth called a “focus” (foci). Where the slip happens below ground. Release of energy starts here...

The Focus of an earthquake can occur at many depths CLASSIFICATION DEPTH OF FOCUS Shallow Focus 0 – 70 km Intermediate Focus 70 – 300 km Deep Focus > 300 km Most Earthquakes have focus less than 100 km deep Earthquakes occur at various depths, depending on the type of tectonic plate interaction involved. Earthquake at a subduction zone could be deeper than one at a transform plate boundary. A shallow focus earthquake causes greater destruction than a deep focus one. About 3% of quakes Shallow Focus earthquakes cause more damage 11

EPICENTER The “epicenter” is the point on the EARTH’s SURFACE directly above the focus. Epicenter is where the shaking is first felt above ground directly above the focus. It is not the center where the Earthquake starts!

Fault Line A fault line is a fracture along which the crust has moved.

Fault FAULT: A surface or narrow zone along which one side has moved relative to the other. Faults are classified based upon their direction of movement.

Three major Faults Normal Reverse Strike-slip

Normal Fault The hanging wall moves down relative to the foot wall. This fault type is caused by tensional stress.

Normal Fault

Reverse Fault The hanging wall moves up relative to the foot wall. This fault is caused by Compressional stress. Hanging Wall is the part of the Earth's crust above the plane of the fault

Reverse Fault

Strike-Slip Fault The fault exists between two pieces of crust and the Movement occurs horizontally where the sides slide past each other. This fault type is caused by shear stress.

Strike Slip Fault

Fault Movement = Earthquakes An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.

Aftershocks Aftershocks are earthquakes that follow the largest shock of an earthquake sequence. They are smaller than the main shock and within 1-2 rupture lengths distance from the main shock. Aftershocks can continue over a period of weeks, months, or years.

Exit Ticket 2.1.1 Match the following terms with their definitions. 1. ___ divergent boundary 2.___ rift valley 3.___ convergent boundary 4.___ transform boundary 5. ___subduction zone 1. B 2. E 3. A 4. D. 5. C