At the end of this lesson you should be able to:

At the end of this lesson you should be able to: • define earthquakes and identify causes • identify how earthquakes are predicted and measured and how they are located • discuss how waves affect a variety of mediums • identify the effects of volcanoes • discuss how we can use models to predict earthquakes or volcanic eruptions

On the white board below, type what you believe causes Earthquakes and/or volcanoes.

Geologic events, such as earthquakes and volcanic eruptions, can be deadly. The basis for all geologic events is plate tectonics: the movements of Earth’s lithospheric plates. Earth's lithospheric plates are in constant motion. Therefore, earthquakes and volcanic eruptions are possible any time. Many of these events are potentially dangerous. Destruction wrought by earthquakes and volcanic eruptions can cost billions of dollars and kill thousands of people. Earthquake.usgs.gov

Locations of Volcanoes The popular conception of a volcano is a high mountain with a hole at the top where the volcano erupts. In fact, a volcano is any location where molten rock and other materials make their way to Earth’s crust and onto the surface. Usually, but not always, volcanoes build mountains, as the once-molten rock hardens on Earth’s surface. Volcanoes are found worldwide, often where two tectonic plates meet. Many of the world’s volcanoes are along the Ring of Fire surrounding the Pacific Ocean. The map below shows the locations of Earth’s tectonic plates and the location of volcanoes.

Effects of Volcanoes Magmais molten rock that forms under Earth’s surface. Lava is molten rock that reaches the surface. There are different kinds of volcanic eruptions Some volcanoes erupt more or less continuously. These eruptions comprise “thinner” lava that oozes out of the volcano, without a violent eruption, they have a type of “quiet” eruption. The lava flows onto the ground and hardens.

Effects of Volcanoes Eruptions can be violent, spewing forth hot chunks of rock, gases, dust and lava. Violent eruptions result when “thick” lava and magma plug the volcano, allowing trapped gases to build up. When the volcano can no longer contain the trapped gases, a violent eruption shoots clouds of dust, gas, and smoke high into the atmosphere. Some eruptions can blow off the top of a mountain, leaving a large crater. The mixture of rock, lava, and ash that spews from a violent eruption is called pyroclastic material. (Pyro-means “fire,” and –clastic mean “pieces.”)

Types of Volcanoes The various types and locations of eruptions lead to different classifications for volcanoes. Composite Volcanoes – are generally steep-sided slopes with violent eruptions. Pyroclastic material and lava build layers within the volcano, making a tall cone. Mount Etna in Italy (Sicily) is a composite volcano. Other examples include Mount St. Helens in Washington and Mount Fuji in Japan.

Cinder Cone Volcano – Cinder is another term used to describe the ash and dust ejected from a volcano. Layers of cinder and lava form mounds of material. Cinder cone volcanoes are usually located near other types of volcanoes. This cinder cone is located on the side of Mount Etna.

Shield volcanoes generally have gently sloping sides. They form because “quiet” lava eruptions build layers over time. The Hawaiian islands are formed by shield volcanoes The Mauna Loa volcano in Hawaii is a shield volcano. The volcano rises from the seafloor, making it the largest volcano on Earth.

Lets test what you have learned so far: 1. The basis for all geologic events is: Aliens Plate Tectonics Earth’s rotation

Lets test what you have learned so far: 1. Many of the world’s volcanoes are along: The equator Sahara Desert The Ring of Fire

Lets test what you have learned so far: 1. These types of volcanoes generally have steep-sided slopes with violent eruptions: Cinder Cone Composite Shield

Earthquakes occur anywhere rock structures are under stress from movement. The upper portion of Earth’s crust is brittle. Tectonic plate motion can cause the crust to break, resulting in an earthquake.

Earthquakes occur most often at transform plate boundaries. The best-known transform plate boundary runs through California. Here, the eastern side of the Pacific Plate meets the western side of the North America Plate. The two plates slide past each other, building stress within the rock structures. The stress causes the rocks to bend. The rocks deform as more stress builds

The deformation transfers energy from the movement of tectonic plates to rock structures. Therefore, deformed rocks along fault lines contain a high amount of potential energy. At some point the rocks can no longer bear the stress and suddenly give way. All the stored energy is released, and an earthquake occurs.

Scientists model the buildup and release of energy in rocks as elastic rebound. In this process, Earth’s rocks are equated to a rubber band. If you pull back a rubber band, it gains potential energy. If you pull far enough, the rubber band snaps, with a sudden release of that energy. In other words, the excessive deformation of the rubber band results in elastic rebound, which we experience as the release of potential energy suddenly transformed to kinetic energy. A similar process takes place when the potential energy of stressed rock is transformed to the kinetic energy of moving rock, an earthquake.

The sudden release of energy where rock ruptures causes seismic waves to move outward in all directions. A seismic wave is any ground movement that results from energy released during an earthquake. The point in the Earth’s crust where the rock ruptures is the focus. The point on Earth’s surface directly above the focus is the epicenter.

Earthquake Waves Earthquakes cause intense shaking of the ground. The shaking is caused by waves moving through the ground. Scientists study the seismic waves using a seismograph (also called a seismometer). These machines record ground movement by making lines on paper. The recorded lines on paper are called a seismogram. Both a seismograph and a seismogram are shown in the images below:

There are two main types of waves, as follows: I. 1st type: Body waves A. P waves 1. Also know as primary waves or compression waves 2. Travel through the solid and liquid parts of Earth 3. Fastest earthquake waves a. Travel about 5 km per second b. Always the 1st waves to appear on seismogram 4. Cause ground to move horizontally back and forth through compression

There are two main types of waves, as follows: I. 1st type: Body waves B. S waves 1. Also know as secondary waves or shear waves 2. Can travel through Earth’s solid portions only 3. When they hit the liquid core, S-waves are no longer able be detected a. P-waves bounce off the liquid core. S-waves are absorbed at the core 4. Cause ground to move back and forth in an S-shaped pattern.

There are two main types of waves, as follows: II. 2nd type: Surface waves A. Rayleigh waves 1. Also known as R-waves 2. Cause intense damage to the surface, especially to buildings 3. Have a rolling motion, like the waves of the ocean

There are two main types of waves, as follows: II. 2nd type: Surface waves B. Love waves 1. Also know a L-waves 2. Cause intense damage to the surface, especially to buildings 3. Have a side-to-side motion similar to the movement of a snake.

Lets test what you have learned so far: 1. Examples include S-waves and P-waves: Body waves Surface waves Ocean waves

Lets test what you have learned so far: 1. The point inside Earth where rock ruptures: Epicenter Elastic Rebound Focus

Lets test what you have learned so far: 1. A machine used to record ground motion: Seismograph Epicenter Seismogram

Predicting earthquakes Stress in rock structures can be measured. Earthquakes are usually sudden, but some rock structures can give clues. For example, there is obvious stress on rocks in the following image. At some point, the rocks will be unable to withstand the stress and will suddenly rupture, causing an earthquake.

Dangers of earthquakes and volcanoes • Dangers associated with earthquakes and volcanoes can include landslides and tsunamis. • A tsunami is a high-speed, long-wavelength wave that happens when large volumes of ocean water are displaced by earthquakes, volcanoes, or underwater landslides. The waves are often mistakenly called “killer waves.” The common depiction of a tsunami as a giant, curved wall of water is also incorrect.

Dangers of earthquakes and volcanoes List one impact that you think earthquakes or volcanoes have on us or the environment:

Lab

Lab: Seismograph 2 Once you click on the seismograph station of your choice, this diagram will appear.

Lab: Measuring P to S Waves To start, you will need to highlight where the P-wave begins and continue highlighting to the start of the S-wave. Did I correctly measure from the P-Wave to the S-Wave? Click the red X for no or the green check for yes

Graphing the Distance

Locating the Epicenter

Epicenter The area where all three circles intersect is known as the _____________. A. P Wave B. S Wave C. Epicenter

Completing the Lab • Once you have completed the lab you will need to complete the questions on the lab document. • When I transfer the lab document to you, you will want to save it and use this later to answer your questions on.

At the end of this lesson you should be able to: