Earthquakes

Forces in Earth’s Crust The movement of Earth’s plates creates enormous forces that _________ or ________ the rock in the crust as if it were a candy bar. These forces are examples of __________, a force that acts on rock to change its shape or volume. A rock’s __________ is the amount of space the rock takes up. Stress adds __________ to the rock.

Forces in Earth’s Crust Types of Stress Three different kinds of stress can occurs in the crust. ______________ Tension, compression, and shearing work over __________________ to change the _________________ of rock.

Forces in Earth’s Crust Tension _______________________________ _______________________________ _______________________________ The __________ on rock is somewhat like pulling apart a piece of warm ______________. Occurs where _________ plates are moving apart.

Forces in Earth’s Crust The stress force called ______________ pulls on the crust, stretching rock so that it becomes _____________ in the middle.

Forces in Earth’s Crust Compression _______________________________ _______________________________ _______________________________ One plate pushing ____________ another can compress rock like a giant ___________________.

Forces in Earth’s Crust The stress force called _______________ squeezes rock until it folds or breaks.

Forces in Earth’s Crust Shearing _______________________________ _______________________________. Can cause rock to break and slip apart or to change its shape.

Forces in Earth’s Crust Stress that pushes a mass of rock in two _________________ is called ____________________.

Forces in Earth’s Crust Kinds of Faults When enough stress builds up in rock, the rock breaks, creating a fault. Recall that a ____________ is a break in the rock of the crust where rock surfaces slip past each other. The rocks on both sides of a fault can move up or down or sideways.

Forces in Earth’s Crust Kinds of Faults Most faults occur along ________________, where the forces of plate motion push or pull the crust so much that the crust breaks. There are _________ main types of faults: _________________

Forces in Earth’s Crust _____________________ Tension in Earth’s crust pulls rock ____________. _______________________________ _______________________________ _______________________________ The block that lies _________ is called the ____________________. The rock that lies _________ is called the ____________________.

Forces in Earth’s Crust Normal Faults When movement occurs along a normal fault, the hanging wall slips ___________. _______________________________ _______________________________. For example, normal faults are found along the __________________ in New Mexico, where two pieces of Earth’s crust are under ____________.

Forces in Earth’s Crust _____________ in Earth’s crust pulls rock apart, causing normal faults. Blue arrows are the force deforming the crust. Red arrows is the movement along the fault.

Forces in Earth’s Crust _____________________ In places where the rock of the crust is pushed together, __________________ causes ______________ faults to form. Has the same structure as a _______________, but the blocks move in the _______________ direction. The rock forming the _____________ of a reverse fault slides up and over the _________. Movement along reverse faults produced part of the northern ____________________ in the western United States and Canada.

Forces in Earth’s Crust A reverse fault has the same structure as a _______________, but the blocks move in the opposite direction.

Forces in Earth’s Crust Strike-Slip Faults ______________________________________ ____________________________________. The rocks on either side of the fault slip past each other sideways, with little up or down _____________. A strike-slip fault that forms the boundary between two plates is called a ____________________. The ______________________ in California is an example of a strike-slip fault that is a transform boundary.

Forces in Earth’s Crust In a strike-slip fault, the rocks on either side of the fault slip past each other sideways, with little up and down motion.

Forces in Earth’s Crust The forces produced by the movement of Earth’s plates can _______________________________ the crust. Over millions of years, the forces of plate movement can change a flat plain into landforms such as _____________ and synclines, ________________, fault- block mountains, and _____________.

Forces in Earth’s Crust Folding Earth’s Crust Sometimes plate movement causes the crust to ______________. Rock stressed by ________________ may bend without ________________. Folds are _____________ in the rock that form when compression shortens and thickens part of Earth’s crust. A fold can be only a few _______________ across or hundreds of ________________ wide. You can often see small folds in the rock exposed where a ____________ has been cut through a hillside.

Forces in Earth’s Crust Geologists use the terms _____________ and _____________ to describe upward and downward folds in rock. A fold in rock that bends upward into an arch is an _______________. A fold in rock that bends downward to form a valley is a ________________. Anticlines and synclines are found in many places where __________________ forces have folded the crust. The central _________________________ in Pennsylvania are folded mountains made up of anticlines and synclines.

Forces in Earth’s Crust Over millions of years, the forces of plate movement can change a flat plain into landforms such as anticlines and synclines, folded mountains, fault-block mountains, and plateaus.

Forces in Earth’s Crust The ___________________ of two plates cause compression and folding of the crust over a wide area. Folding produced some of the world’s largest __________________________. The _______________in Asia and the _________in Europe formed when pieces of the crust folded during the collision of two _________________.

Forces in Earth’s Crust Stretching Earth’s Crust When two normal faults cut through a block of rock, a ______________________ forms. How does this process begins? _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ ______________________________________.

Forces in Earth’s Crust Over millions of years, the forces of plate movement can change a flat plain into landforms such as anticlines and synclines, folded mountains, fault-block mountains, and plateaus.

Forces in Earth’s Crust Uplifting Earth’s Crust The forces that raise mountains can also uplift, or raise, ______________. A ___________ is a large area of flat land elevated high above __________. Some plateaus form when forces in Earth’s _________push up a large, flat ___________ of rock. A plateau consists of many _________flat layers, and is wider than it is tall.

Earthquake and Seismic Waves An ________________ is the shaking and trembling that results from the movement of rock beneath Earth’s surface. The forces of ___________________ cause earthquakes. Plate movements produce ___________ in Earth’s ______________, adding energy to rock and forming faults.

Earthquake and Seismic Waves Stress _________________ along a fault until the rock breaks. An earthquake begins. Most earthquakes begin in the _____________ within about _______ kilometers of Earth’s surface. The ___________ is the area beneath Earth’s surface where rock that is under _________ breaks, triggering an earthquake. The point on the surface directly above the focus is called the ______________.

Earthquake and Seismic Waves Types of _________________ An earthquake produces ____________ called ___________. These waves carry __________ as they travel ______________. During an earthquake, seismic waves race out from the ________ in all directions. ________________ are vibrations that travel through Earth carrying the energy released during an earthquake.

Earthquake and Seismic Waves Seismic waves carry energy from an earthquake away from the focus, through Earth’s ___________, and across the ______________. There are ______ main categories of seismic waves. ________________ An earthquake sends out ______ types of waves from its focus: ____________________________ When these waves reach Earth’s surface at the epicenter, ________________ develop.

Earthquake and Seismic Waves Seismic waves carry energy from an earthquake away from the focus, through Earth’s interior, and across the surface.

Earthquake and Seismic Waves P waves The ____________ waves to arrive are ______________ waves or P waves. Seismic waves that compress and expand the ground like an _______________. ____________________.

Earthquake and Seismic Waves

___________________ After P waves come _____________ waves, or S waves. Seismic waves that vibrate from _____________ as well as _____________. They shake the __________ back and forth. When they reach the surface, they shake structures _______________. Unlike P waves, which travel through both __________________, S waves cannot move through ________________.

Earthquake and Seismic Waves

_______________ Waves When P waves and S waves reach the ______________, some of them become ______________ waves. Move more __________ than P waves and S waves, but they can produce ___________________ movements. Some make the ground roll like _________ waves. Others shake buildings from ___________.

Earthquake and Seismic Waves

Measuring Earthquakes There are at least _______ different measures for rating earthquakes, each with its strengths and short comings. ___________ commonly used methods of measuring earthquakes are: ____________________

Earthquake and Seismic Waves The Mercalli Scale _______________________________ _______________________________ _______________________________. The _____ steps of this scale describe an earthquake’s effects. The same earthquake can have __________ Mercalli ratings because it caused different amounts of ground motion at different locations.

The Mercalli Scale

Earthquake and Seismic Waves ________________________ An earthquake’s _______________ is a number that geologists assign to an earthquake based on the earthquake’s size. Geologists determine magnitude by measuring the ____________ and __________ movement that occur during an earthquake. The Richter Scale is a ____________ of an earthquake’s _____________ based on the _______ of the earthquake’s seismic waves.

Earthquake and Seismic Waves The seismic waves are measured by a ________________. A seismograph is an ______________ that ________________ and _____________ seismic waves. The Richter scale provides ____________ measurements for small, nearby earthquakes.

Earthquake and Seismic Waves The ______________________ Scale A rating system that _____________ the total energy released by an earthquake. Can be used to rate earthquakes of all _____________, near or far. You may hear news reports that mention the Richter scale, but the number they quote is almost always the moment magnitude for that earthquake.

Earthquake and Seismic Waves To rate an earthquake on the moment magnitude scale, geologist first study ___________ from seismographs. The data show what kinds of __________________ the earthquake produced and how strong they were. The data also help geologists ______ how much movement occurred along the fault and the strength of the rocks that broke when the fault slipped.

Earthquake and Seismic Waves Comparing Magnitudes Earthquake’s _______________ tells geologists how much ___________ was released by the earthquake. Each _______________ increase in magnitude represents the release of roughly _________ times more energy. The effects of an earthquake ______________ with magnitude.

Earthquake and Seismic Waves Earthquakes with a magnitude below ___ are small and cause ________ damage. Those with a magnitude between __ and __ can cause moderate damage. Earthquakes with a magnitude ______ 6 can cause ________ damage. The most powerful earthquakes, with a magnitude of ____ or above, are rare.

Earthquake and Seismic Waves Locating the __________________ Geologists use ____________ waves to locate an earthquake’s epicenter. P waves arrive at a seismograph _______, with ____ waves following close behind. To tell how far the epicenter is from the seismograph, scientists measure the _____________ between the arrival times of the P waves and S waves. The ___________ away an earthquake is, the ___________ the time between the arrival of the P waves and the S waves.

Earthquake and Seismic Waves Geologists then draw at least three _____________ using data from different seismographs set up at ___________ all over the _____________. The ____________ of each circle is a particular seismograph’s location. The __________ of each circle is the distance from that seismograph to the ____________.

Monitoring Earthquakes The Seismograph A _____________ seismograph can consist of a heavy weight attached to a frame by a spring or wire. Seismic waves cause the seismograph’s _______ to vibrate. But the suspend weight with the pen attached moves very little. Therefore, the _____ stays in place and records the drum’s vibrations.

Monitoring Earthquakes Measuring Seismic Waves In a seismograph, it’s the pen that remains ______________ while the paper moves. All seismographs make use of a basic principle of ___________: Whether is it moving or at rest, every object resists

Monitoring Earthquakes Reading a Seismogram The pattern of lines, called a ______________, is the record of an earthquake’s seismic waves produced by a seismograph.

Monitoring Earthquakes

How Earthquakes Cause Damage When a major earthquake strikes, it can cause great damage. Causes of earthquake damage include shaking, liquefaction, aftershocks, and tsunamis.

Earthquake Risk

Monitoring Earthquakes Shaking Produced by seismic waves can trigger _______________________________. Can also damage or destroy _________ and ________, topple utility _______, and fracture gas and water _________. The types of _______________ determine where and how much the ground shakes. The most ______________ shaking may occur kilometers away from the epicenter. ____________ soil shakes more violently than _____________ rock.

Monitoring Earthquakes __________________ _______________________________ _______________________________ _______________________________. Is likely where the soil is full of _______________. As the ground gives way, buildings _______ and _______ apart.

Monitoring Earthquakes __________________ Sometimes, buildings weakened by an earthquake _______________ during an _________________. _______________________________ ______________________________. May strike ________, __________, or even ____________ later.

Monitoring Earthquakes _______________ When an earthquake __________ the ocean floor, _________________ causes the ocean floor to rise slightly and push water out of its way. The water ________________ by the earthquake may form a large wave. Spreads out from an earthquake’s _____________ and _____________ across the ocean. As a tsunami approaches ______________ water, the wave grows into a mountain of water.

Monitoring Earthquakes