Presentation on theme: "2010 Dynamic Planet: Earthquakes and Volcanoes Presented by Linder Winter."— Presentation transcript:
2010 Dynamic Planet: Earthquakes and Volcanoes Presented by Linder Winter
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1. DESCRIPTION Students will use process skills to complete tasks related to earthquakes and volcanoes. A team of up to: 2 Approximate time: 50 minutes
2. EVENT PARAMETERS Each team may bring one 8.5” x 11” two-sided page of notes containing information in any print format from any source. Each participant may also bring a “non-graphing” calculator.
THE COMPETITION Participants will be presented with one or more tasks, many requiring the use of process skills (i.e. observing, classifying, measuring, inferring, predicting, communicating and using number relationships – source: AAAS) for any of the following topics: Each addressed separately.
Coaching Tips and Hints: Resources Resources are to knowledge events as projects are to construction events. Students develop their own resources; no hand-me-downs! Participant-produced resources provide an oppor-tunity for coaches to frequently and easily monitor participant progress. Encourage continual revision of resources, i.e. after each level of competition, when participants feel confident with their knowledge of specific topics, etc.
Coaching Tips and Hints: Resources Suggested items to include in student resources: Definitions Characteristics of the various types of volcanoes Diagrams and illustrations Characteristics of P, S and surface seismic waves
Coaching Tips and Hints With the growing complexity of the events, it is very difficult, if not impossible, to coach all the events without assistance. Should you find someone willing to coach the Earthquakes and Volcanoes event, give him/her a copy of this PowerPoint presentation to provide an overview of the event.
Representative Activities Interpretation of charts, tables, diagrams (many of the diagrams included in this presentation may be developed into an activity. Locating the epicenter of a volcano Patterns of volcanic and earthquake patterns around the world (mapping) Identification of volcanic features Match volcanic features with popular examples, i.e. Devil’s Tower – Volcanic Neck; Crater Lake – Caldera
Coaches’ Resources Information on all topics identified in the event rules may easily be found on the web. Choice of “key words and phrases” are the keys to success! Be certain to caution participants to use only professional websites in their search for information. These include the USGS, college sites, etc. Middle/Junior/Senior High Earth Science Textbooks, and even Introductory college textbooks *The Game of Earth, NEW 2010 Edition *The Theory of PLATE TECTONICS CD *http://www.otherworlds-edu.com
a. Worldwide distribution patterns of earthquakes and volcanoes
Types of Volcanoes: Shield Volcanoes Shield volcanoes are huge in size. They are built up by many layers of runny lava flows spilling out of a central vent or group of vents. The broad shaped, gently- sloping cone is formed from basaltic lava which does not pile up into steep mounds.
Types of Volcanoes: Stratovolcanoes (Composite) Tall, conical volcanoes with many layers (strata) of hardened lava, tephra and volcanic ash Characterized by steep profiles and periodic, explosive eruptions Lava tends to be viscous (very thick) Common at subduction zones where oceanic crust is drawn under continental crust
Types of Volcanoes: Cinder Cones A cinder cone is a steep conical hill of volcanic fragments that accumulate around and downwind from a volcanic vent. The rock fragments, often called cinders or scoria, are glassy and contain numerous gas bubbles "frozen" into place as magma exploded into the air and then cooled quickly. Cinder cones range in size from tens to hundreds of meters tall. Cinder cones are made of pyroclastic material.
CONTROLS ON EXPLOSIVITY: Possible interpretive activity SiO2 MAGMATEMPERATURE VISCOSITY GAS ERUPTION STYLE TYPE(centigrade)CONTENT ~50%mafic~1100 low nonexplosive ~60%intermediate ~1000 intermediate ~70%felsic ~800high explosive
Explosive vs. Effusive
Types of Volcanoes: Active, Dormant, Extinct (According to U.S.G.S.) An active volcano to volcanologists is a volcano that has shown eruptive activity within recorded history. A dormant volcano is somewhere between active and extinct. A dormant volcano is one that has not shown eruptive activity within recorded history, but shows geologic evidence of activity within the geologic recent past. An extinct volcano is one that is both inactive and unlikely to erupt again in the future. An extinct volcano is a volcano that has not shown any historic activity, is usually deeply eroded, and shows no signs of recent activity.
Volcanic Hazards Potential activity!
Primary Volcanic Hazards: Pyroclastic Flows Pyroclastic flows are fast-moving, avalanche-like, ground- hugging incandescent mixtures of hot volcanic debris, ash, and gases that can travel at speeds in excess of 150 km per hour.
Primary Volcanic Hazards: Lahars Lahars, also known as mud flows or debris flows, are slurries of muddy debris and water caused by mixing of solid debris with water, melted snow, or ice.
Primary Volcanic Hazards: Tephra Tephra (ash and coarser debris) is composed of fragments of magma or rock blown apart by gas expansion. Tephra can cause roofs to collapse, endanger people with respiratory problems, and damage machinery. Tephra can clog machinery, severely damage aircraft, cause respiratory problems, and short out power lines up to hundreds of miles downwind of eruptions.
Primary Volcanic Hazards: Gases The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride and hydrogen fluoride. A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen, carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides.
Primary Volcanic Hazards: Lava Flows Lava flows are generally not a threat to people because generally lava will move slowly enough to allow people to move away; thus they are more of a property threat.
Primary Volcanic Hazards: Flood Basalts A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Image: Moses Coulee showing former, multiple flood basalt flows of the Columbia River Basalt Group.
Secondary Volcanic Hazards: Flooding Drainage systems can become blocked by deposition of pyroclastic flows and lava flows. Such blockage may create a temporary dam that could eventually fill with water and fail resulting in floods downstream from the natural dam. Volcanoes in cold climates can melt snow and glacial ice, rapidly releasing water into the drainage system and possibly causing floods.
Secondary Volcanic Hazards: Famine Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degrees Fahrenheit for periods of one to three years. Tephra falls can cause extensive crop damage and kill livestock which may lead to famine.
Types of Earthquakes: Spreading Center An oceanic spreading ridge is the fracture zone along the ocean bottom where molten mantle material comes to the surface, thus creating new crust. This fracture can be seen beneath the ocean as a line of ridges that form as molten rock reaches the ocean bottom and solidifies
Types of Earthquakes: Subduction Zone Major earthquakes may occur along subduction zones. The most recent sub- duction zone type earth- quake occurred in Scientists believe, on average, one subduction zone earthquake occurs every years.
Types of Earthquakes: Transform Fault A transform fault is a special variety of strike- slip fault that accommo- dates relative horizontal slip between other tectonic elements, such as oceanic crustal plates
Types of Earthquakes: Intraplate Intraplate seismic activity occurs in the interior of a tectonic plate. Intraplate earthquakes are rare compared to earthquakes at plate boundaries. Very large intraplate earthquakes can inflict very heavy damage. Distribution of seismicity associated with the New Madrid Seismic Zone since 1974.
Primary Earthquake Hazards: Rapid Ground Shaking Ground shaking, a principal cause of the partial or total collapse of structures, is the vibration of the ground. The first wave to reach the earth's surface, the P wave, causes a building to vibrate. The most damaging waves are shear waves, S waves, which travel near the earth's surface and cause the earth to move at right angles to the direction of the wave and structures to vibrate.
Secondary Earthquake Hazards: Rapid Ground Shaking Alterations to Water CoursesFire resulting from an earthquake
Earthquake Hazards: Shake Map The Shake Map for the 1994 magnitude 6.7 Northridge, CA earth-quake shows the epicenter at the location of the green star. The intensity of shaking created by the earthquake is shown by the different color gradients on the map. The magnitude of the earthquake is 6.7 no matter where you are, but the intensities vary by location.
Structural Engineering Practices Early alert capabilities in some cases will allow some systems to automatically shut down before the strong shaking starts so that the services and people using them will be safe. Such systems may include elevators, utilities such as water and gas, and factory assembly lines.
Volcanic Monitoring: Geologic History The first thing scientists do is determine a volcano's eruption history. A volcano is classified as active, dormant or extinct based upon when it has last erupted. Active volcanoes are in the process of erupting or show signs of eruption in the very near future. Dormant volcanoes are "sleeping." This means they are not erupting at this time, but they have erupted in recorded history. An extinct volcano has not erupted in recorded history and probably will never erupt again.
Volcanic Monitoring: Associated Earthquake Activity Each type of ground-shaking event usually generates a unique seismic "signature" that can be recognized and identified as having been "written" by a specific event.
Volcanic Monitoring: Magma Movement Earthquake activity beneath a volcano almost always increases before an eruption because magma and volcanic gas must first force their way up through shallow underground fractures and passageways. When magma and volcanic gases or fluids move, they will either cause rocks to break or cracks to vibrate. When rocks break high-frequency earthquakes are triggered. However, when cracks vibrate either low-frequency earthquakes or a continuous shaking called volcanic tremor is triggered.
Volcanic Monitoring: Satellite Data Satellites can record infrared radiation where more heat or less heat shows up as different colors on a screen. If a volcano is seeming to become hotter, then an eruption may be coming soon.
Volcanic Monitoring: Hazard Maps
Earthquake Monitoring: Identification of Faultlines New Madrid, TennesseeSan Andreas Faultline
Earthquake Monitoring: Remote Seismograph Positioning Scientists consider seismic activity as it is registered on a seismometer. A volcano will usually register some small earthquakes as the magma pushes its way up through cracks and vents in rocks as it makes its way to the surface of the volcano. As a volcano gets closer to erupting, the pressure builds up in the earth under the volcano and the earthquake activity becomes more and more frequent.
Earthquake Monitoring: Analog vs. Digital Below is a digital seismogram. The data is stored electronically, easy to access and manipulate, and much more accurate and detailed than the analog recordings. This is an image of an analog recording of an earthquake. The relatively flat lines are periods of quiescence and the large and squiggly line is an earthquake.
Earthquake Monitoring: Tiltmeter When a volcano is about to erupt, the earth may bulge or swell up a bit. Tiltmeters attached to the sides of a volcano detect small changes in the slope of a volcano. Installing a tiltmeter
Earthquake Monitoring: Changes in Groundwater Levels Hydrogeologic responses to large distant earthquakes have important scientific implications with regard to our earth’s intricate plumbing system. The exact mechanism linking hydrogeologic changes and earthquakes is not fully understood, but monitoring these changes improves our insights into the responsible mechanisms, and may improve our frustratingly imprecise ability to forecast the timing, magnitude, and impact of earthquakes.
Earthquake Monitoring: Observations of Strange Behaviors in Animals The cause of unusual animal behavior seconds before humans feel an earthquake can be easily explain-ed. Very few humans notice the smaller P wave that travels the fastest from the earthquake source and arrives before the larger S wave. But many animals with more keen senses are able to feel the P wave seconds before the S wave arrives. If in fact there are precursors to a significant earthquake that we have yet to learn about (such as ground tilting, groundwater changes, electrical or magnetic field variations), indeed it’s possible that some animals could sense these signals and connect the perception with an impending earthquake.
Volcanism at Plate Boundaries Encyclopædia Britannica, Inc.
Volcanism Over Hot Spots (Oceanic and Continental)
Volcanism: Hydrothermal Vents A hydrothermal vent is a geyser on the seafloor. In some areas along the Mid- Ocean Ridge, the gigantic plates that form the Earth's crust are moving apart, creating cracks and crevices in the ocean floor. Seawater seeps into these openings and is heated by the molten rock, or magma, that lies beneath the Earth's crust. As the water is heated, it rises and seeks a path back out into the ocean through an opening in the seafloor.
Plate Boundaries: Divergent Plate Boundaries Divergent plate boundaries are locations where plates are moving away from one another. This occurs above rising convection currents.
Plate Boundaries: Ocean-Ocean Convergence When two oceanic plates converge one is usually subducted under the other and in the process a deep oceanic trench is formed. Oceanic-oceanic plate convergence also results in the formation of undersea volcanoes.
Plate Boundaries: Ocean-Continent Convergence When an oceanic plate pushes into and subducts under a continental plate, the overriding continental plate is lifted up and a mountain range is created. This type of convergent boundary is similar to the Andes or the Cascade Range in North America.
Plate Boundaries: Continent to Continent Convergence When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust tends to buckle and be pushed upward or sideways.
Plate Boundaries: Divergent Plate Boundaries - Oceanic When a divergent boundary occurs beneath oceanic lithosphere, the rising convection current below lifts the lithosphere producing a mid-ocean ridge.
Plate Boundaries: Divergent Plate Boundaries - Continental When a divergent boundary occurs beneath a thick continental plate, the pull-apart is not vigorous enough to create a clean, single break through the thick plate material. Here the thick continental plate is arched upwards from the convection current's lift, pulled thin by extensional forces, and fractured into a rift-shaped structure.
Plate Boundaries: Transform Plate Boundaries at Mid-Ocean Ridges Transform-Fault Boundaries are where two plates are sliding horizontally past one another. These are also known as transform boundaries or more commonly as faults. Most transform faults are found on the ocean floor. They commonly offset active spreading ridges, producing zig-zag plate margins, and are generally defined by shallow earthquakes.
Plate Boundaries: Rifting of Continental Plates
Plate Tectonics: Seafloor Spreading Sea-floor spreading — In the early 1960s, Princeton geologist Harry Hess proposed the hypothesis of sea-floor spreading, in which basaltic magma from the mantle rises to create new ocean floor at mid-ocean ridges. On each side of the ridge, sea floor moves from the ridge towards the deep-sea trenches where it is subducted and recycled back into the mantle
Geographical features associated with Plate Tectonics Mid-ocean ridges - Long mountain chains on the sea-floor that are elevated relative to the surrounding ocean floor. Trenches - Deep, arcuate features, typically at the borders of the oceans where oceanic crust meets continental crust. Trenches also occur where one oceanic plate is diving below another oceanic plate.
Geographical features associated with Plate Tectonics Fracture zones - Lie outboard of transform faults where the fault ends and so the same plate borders both sides of the "fault." The fracture zones record sites of past faulting activity. Mid-Plate volcanoes - A broad term to explain the many volcanoes found far away from the spreading center, or mid-ocean ridge. The volcanoes formed either due to hot spots, or actually formed at the spreading center but were carried away along with the plate. Over time, the volcanoes stop accreting new material and sink below sea level as the oceanic crust cools. Sea mounts are volcanoes below sea level, and guyots are volcanoes below sea level in which the top has been planed off. Very old submerged volcanoes can become abyssal hills.
Geographical features associated with Plate Tectonics Island or volcanic arcs - Found adjacent to trenches. Site where the rising magma from the subducting plate reaches the surface. These chains are arcuate owing to the spherical geometery of the Earth. Typically, these volcanoes have a mixed lithology between continental and oceanic crust (andesite).
Evidence of Sea Floor Spreading: Magnetic Reversals Magnetism on the ocean floor is orderly, arranged in long strips. The strips on the Atlantic ocean floor, in particular, are parallel to the mid- Atlantic ridge. Their structure and distribution are remarkably symmetric on both sides.
Evidence of Sea Floor Spreading: Age of Sea Floor as Opposed to Continents Scientists use the magnetic polarity of the sea floor to determine the age. Very little of the sea floor is older than 150 million years. This is because the oldest sea floor is subducted under other plates and replaces by new surfaces. The tectonic plates are constantly in motion and new surfaces are always being created. This continual motion is evidenced by the occurrence of earthquakes and volcanoes.
Evidence of Sea Floor Spreading: Fossil Evidence
Density Differences between Continental and Oceanic Plates Continental margin - Because of the density difference between continental and oceanic crust, a particular geometry develops where the two types of crust meet. Starting from the continent, there is first a broad, flat zone called the "continental shelf." Then, near the end of continental crust, the angle increases and the area is called the "continental slope." Further out, at the actual border between the two crusts, the slope decreases, thus the "continental rise."
Faults: Dip-Slip - Normal Normal faults happen in areas where the rocks are pulling apart (tensile forces) so that the rocky crust of an area is able to take up more space. The rock on one side of the fault is moved down relative to the rock on the other side of the fault. Normal faults will not make an overhanging rock ledge. In a normal fault it is likely that you could walk on an exposed area of the fault.
Faults: Dip-Slip - Reverse Reverse faults happen in areas where the rocks are pushed together (compression forces) so that the rocky crust of an area must take up less space. The rock on one side of the fault is pushed up relative to rock on the other side. In a reverse fault the exposed area of the fault is often an overhang. Thus you could not walk on it. Thrust faults are a special type of reverse fault. They happen when the fault angle is very low.
Transform (strike-slip) Faults The movement along a strike slip fault is horizontal with the block of rock on one side of the fault moving in one direction and the block of rock along the other side of the fault moving in the other direction. Strike slip faults do not make cliffs or fault scarps because the blocks of rock are not moving up or down relative to each other.
Faults: Normal and Reverse Normal – Normal faults form when the hanging wall drops down. The forces that create normal faults are pulling the sides apart (extensional). Reverse – Reverse faults form when the hanging wall moves up. Forces creating reverse faults are compressional, pushing the sides together.
HANGING WALL VS FOOTWALL Vertical faults are the result of up or down movement along a break in the rocks. Actually, both blocks may move up or both blocks may drop, or one might go up and one might go down. It is the end result of the movement that classifies the relationship between the blocks.
HANGING WALL VS FOOTWALL The hanging wall block is the one on the left and the foot wall block is the one on the right.
Faults: Strike-Slip Strike-slip faults have walls that move sideways, not up or down. The forces creating these faults are lateral or horizontal, carrying the sides past each other.
Faults: Transform Transform boundaries occur when the two plates move past one another. This is primarily a function of equal density of the plates; however, it also occurs due to the direction of movement. That is, if the direction of movement of the two plates is parallel but opposite, the plates will neither subduct nor diverge. The boundary of movement is called the transform fault. In reality, it is rarely a singular fault but rather a zone. Outlying the transform faults are records of past tectonic activity called "fracture zones."
Climatic Effects of Volcanic Ejecta Volcanic dust blasted into the atmosphere causes temporary cooling. Volcanoes that release huge amounts of sulfur compounds affect the climate more strongly than those that eject just dust. Combined with atmospheric water, they form a haze of sulfuric acid that reflects a great deal of sunlight which may cause global cooling for up to two years. Much more at:
Tsunamis: Origin Tsunamis can be generated by: Large Earthquakes (megathrust events such as Sumatra, Dec. 26, 2004) Underwater or near-surface volcanic eruptions (Krakatoa, 1883) Comet or asteroid impacts (evidence for tsunami deposits from the Chicxulub impact 65 mya) Large landslides that extend into water (Lituya Bay, AK, 1958) Large undersea landslides (evidence for prehistoric undersea landslides in Hawaii and off the east coast of North America)
Tsunamis: Wave Characteristics Tsunami wave propagation characteristics – note that as water depth becomes smaller, waves slow down, become shorter wavelength, and have larger amplitude.
Tsunamis: Warning System A tsunami warning system is a system to detect tsunamis and issue warnings to prevent loss of life and property. It consists of two equally important components: (1) a network of sensors to detect tsunamis and (2) a communications infrastructure to issue timely alarms to permit evacuation of coastal areas. Tsunami Monitoring Buoy: Reports rises in the water column and tsunami events
Stages in the “life” of a Tsunamis : Initiation Near the source of sub- marine earthquakes, the seafloor is "permanently" uplifted and down-dropped, pushing the entire water column up and down. The potential energy that results from pushing water above mean sea level is then transferred to horizontal propagation of the tsunami wave (kinetic energy).
Stages in the “life” of a Tsunamis: Split Within several minutes of the earthquake, the initial tsunami is split into a tsunami that travels out to the deep ocean (distant tsunami) and another tsunami that travels towards the nearby coast (local tsunami).
Stages in the “life” of a Tsunamis: Amplification Several things happen as the local tsunami travels over the continental slope. Most obvious is that the amplitude increases. In addition, the wavelength decreases. This results in steepening of the leading wave--an important control of wave runup at the coast.
Stages in the “life” of a Tsunamis: Runup Tsunami runup occurs when a peak in the tsunami wave travels from the near-shore region onto shore. Runup is a measure-ment of the height of the water onshore observed above a reference sea level.
Seismic Waves: Primary (P) P-waves are the fastest type of seismic wave. As P- waves travel, the surrounding rock is repeatedly compressed and then stretched. (Note: S and P waves are classified as “body” waves.)
Seismic Waves: Secondary (S) S-waves arrive after P- waves because they travel more slowly. The rock is shifted up and down or side to side as the wave travels through it.
Seismic Waves: Surface Waves Rayleigh waves, also called ground roll, travel like ocean waves over the surface of the Earth, moving the ground surface up and down. They cause most of the shaking at the ground surface during an earthquake. Love waves are fast and move the ground from side to side.
Seismic Waves: Primary (P) The fastest wave, and therefore the first to arrive at a given location. Also known as compressional waves, the P wave alternately compresses and expands material in the same direction it is traveling. Can travel through all layers of the Earth. USGS
Seismic Waves: Secondary Waves (S) The S wave is slower than the P wave and arrives next, shaking the ground up and down and back and forth perpendicular to the direction it is traveling. Also know as shear waves. USGS
Seismic Waves: Surface Waves Surface waves follow the P and S waves. Also known as Rayleigh and Love waves. These waves travel along the surface of the earth. USGS
Seismic Waves Measurement: Intensity vs. Magnitude Intensity scales measure the amount of shaking at a particular location. The intensity of an earthquake will vary depending on where you are. Magnitude scales, like the Richter magnitude and moment magnitude, measure the size of the earthquake at its source. Magnitude does not depend on where the measurement of the earthquake is made. On the Richter scale, an increase of one unit of magnitude (for example, from 4.6 to 5.6) represents a 10-fold increase in wave amplitude on a seismogram or approximately a 30-fold increase in the energy released.
Seismic Waves Measurement: Intensity I. Not felt except by a very few under especially favorable conditions. II. Felt only by a few persons at rest, especially on upper floors of buildings. III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated. IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably. V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop. VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight. VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. VIII. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. IX. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. X. Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent. XI. Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly. XII. Damage total. Lines of sight and level are distorted. Objects thrown into the air.
Seismic Waves Measurement: Focal Depth The vibrations produced by earthquakes are detected, recorded, and measured by instruments call seismographs. The zig-zag line made by a seismograph, called a "seismogram," reflects the changing intensity of the vibrations by responding to the motion of the ground surface beneath the instrument. From the data expressed in seismograms, scientists can determine the time, the epicenter, the focal depth, and the type of faulting of an earthquake and can estimate how much energy was released.
5. Scoring Points will be awarded for the quality and accuracy of responses. Ties will be broken by the accuracy and/or quality of answers to pre-selected questions.
7. NATIONAL SCIENCE EDUCATION STANDARDS Content Standard D. Structure of the Earth System; Earth’s history.
Additional Resources Volcanic Hazards & Prediction of Volcanic Eruptions: m m NSTA PowerPoint Presentation on Tsunamis unami!.ppt Hydrothermal vents 2/geology/vents.html Plate boundaries
Additional Resources PowerPoint of Seafloor Spreading _Ch19_03.pdf Windows to the Universe: Earthquakes quake_1.html