Introductory Earth & Earthquake-science Lectures

How can I describe Earth and plate-tectonic processes?

Earthquake science can be daunting to teach, and how it is presented affects understanding. In this series of videos, analogies are used to clarify complex topics as we cover the fundamentals of plate tectonics and the basics of earthquakes.

 The treatment of plate tectonics emphasizes how the distribution and properties of plates and the motions at different kinds of plate boundaries explain global-scale patterns of earthquakes and volcanoes. Themes of the introduction to earthquakes are the nature of seismic waves, the geographic, depth, and size distribution of earthquakes, and the interplay of forces, faults, and friction that account for where and when earthquakes occur.

These clips are taken from an educational workshop on earthquakes and plate tectonics for middle-school, Earth-science teachers in 2007. Dr. Robert Butler explains clearly and clears up misconceptions. How Earth science is presented affects understanding.

Key Points:

Topics covered:

  • Layers of the Earth
  • Plate tectonics
  • Earthquake magnitude
  • Seismic wave behavior.
  • Analogies are used to clarify concepts

Earth Vs. the Egg: Measuring Earth's Layers

This classroom lecture presents a simple conceptual model of the relative thicknesses of the Lithosphere by measuring a simple hard-boiled egg. The hard-boiled egg is used as a scale model for the zones of the Earth. The shell is to the egg as the lithosphere is to the Earth. This demonstration highlights the idea that the lithosphere is a thin shell.

Video Novice
Tectonic (lithospheric) Plates: Commonly confused with crust

Video lecture on four basic types of plate tectonic boundaries: divergent (spreading), transform (strike-slip), and convergent (subduction and continental collision) types of plate boundaries. Clarifies what the tectonic, or lithospheric plates are. Lithospheric plates have two parts consisting of crust and upper mantle. This was recorded at a workshop for middle-school Earth-science teachers in 2006 by Dr. Robert Butler

Video Novice
Asthenosphere: Using Silly Putty as an Analogy

There are many misconceptions about the asthenosphere. This classroom demonstration on the viscoelastic properties of the asthenophere region of Earth's mantle below the lithospheric plates. Silly Putty is used as a model to show how the asthenosphere is elastic when exposed to short-duration forces (like seismic waves) but plastic when exposed to long-duration forces (like the load of the Hawaiian Islands on the Pacific Plate). Lecture by Dr. Robert Butler, University of Portland, Oregon.

Classroom activity is included.

Video Novice
Brittle Vs. Ductile: Big Hunk as a Model for Earth's Crust & Mantle

Video lecture on how temperature controls mechanical behavior of materials, including rocks. A Big Hunk candy bar is used as a model for the behavior of materials in the lower lithosphere. The cold candy bar is brittle while the warm candy bar is ductile or plastic.

Dr. Robert Butler, University of Portland, OR shows that a material can be either ductile or brittle; temperature can control the mechanical behavior of a material; and a Big Hunk candy bar can be used as a model for the lithosphere

Video Novice
Pasta Quake: Modeling magnitude scale using Spaghetti

And how can uncooked spaghetti noodles help teach about the logarithmic nature of the magnitude scale? 

Understanding the magnitude change, thus the relative energy released from say, magnitude 7 to magnitude 8 can be challenging. Dr. Robert Butler (Univ. Portland) uses spaghetti to illustrate the concept by breaking pasta to show how each step up in magnitude represents a huge jump in the size of the pasta bundles. Each step in magnitude is represented by 32 times more spaghetti noodles.

In this video Dr. Butler rounded down to a factor of 30 to simplify the multiplication. 

But, technically speaking, whole unit of magnitude represents approximately 32 times (actually 10**1.5 times) the energy, based on a long-standing empirical formula that says log(E) is proportional to 1.5M, where E is energy and M is magnitude. This means that a change of 0.1 in magnitude is about 1.4 times the energy release.

This explains why big quakes are so much more devastating than small ones. The amplitude ("size") differences are big enough, but the energy ("strength") differences are huge. The amplitude numbers are neater and a little easier to explain, which is why those are used more often in publications. But it's the energy that does the damage.

Video Novice
Elastic Rebound Demonstration using a Yardstick

Dr. Butler talks about elasticity and brittle material using a yardstick as a mechanical analog for the lithosphere. The yardstick is a brittle material that has elastic properties, yet, like the lithosphere, is capable of generating earthquakes.

The lithosphere is brittle yet elastic. A yardstick is also brittle yet elastic and both are capable of storing energy and rebounding elastically. Both are also cabable of breaking and generating earthquakes. This demo shows why it is difficult to predict earthquakes.

Video lecture of Dr. Robert Butler, University of Portland speaking to middle-school teachers.

Video Novice
Faulting & Folding (Foam Faults Demo)

Video lecture demonstrates the use of foam faults to demonstrate faults, and a deck of cards to demonstrate folds and fabrics in rock layers. Different types of faults include: normal (extensional) faults; reverse or thrust (compressional) faults; and strike-slip (shearing) faults.

Video Novice
Plate Boundaries: Convergent, Divergent, Transform

Video lecture on divergent, transform, and convergent types of plate boundaries. Recorded during a 2007 teacher workshop on earthquakes and tectonics. Speaker is Dr. Robert Butler, University of Portland Oregon

Three main types of plate boundaries:

  • Divergent: extensional; the plates move apart. Spreading ridges, basin-range
  • Convergent: compressional; plates move toward each other. Includes: Subduction zones and mountain building.
  • Transform: shearing; plates slide past each other. Strike-slip motion.
Video Novice
Epicenter and Focus (hypocenter) of an Earthquake
Epicenter is the place on Earth's surface directly above the focus, or hypocenter, where the earthquake happened. (Recorded during a 2007 teacher workshop on earthquakes and tectonics. Speaker is Dr. Robert Butler, University of Portland Oregon)
Video Novice
Human Wave: Modeling Seismic Waves in the Classroom

How can I get across the idea in a classroom activity using no props?
Given the motion behavior for the human wave, can you guess which wave, P or S will be faster?Can I model a liquid core using this method?

Roger Groom* has his class model P and S seismic waves through solids and liquids.

This is a DRAFT version to be updated. Caveats include:  The arms-over-shoulders method is a far better analogy to hand-holding method for best physics as noted in subtitles in the video. With hand holding, energy propagates down the line due to internal energy from the particles (the brain telling the other arm to raise)  rather than transferring from one particle to the next as in the arms-over-shoulders method that happens automatically.

NOTES FOR TEACHING:

This demo is a simplified model of natural phenomena. As such it is especially important to emphasize both the strengths and weaknesses of the model to students. Such an explicit discussion helps students focus on the model as a conceptual representations rather than a concrete copy of reality. See Key points below.

*Mount Tabor Middle School, Portland OR

Video Novice
Seismic Slinky: Modeling P and S waves in the classroom

Roger Groom, science teacher at Mount Tabor Middle School, demonstrates how a slinky is a good analogy for P & S seismic waves. He also points out where the model fails to fully mimic seismic-wave behavior.  Slinkies prove to be a good tool for modeling the behavior of compressional P waves and shearing S waves. We recommend reading about the behavior of seismic waves and watching the variety of animations linked to this animation to understand how they travel, and how the P, S, and surface waves differ from each other.

Video Novice
Seismic Waves: P, S, and Surface

Video lecture on wave motions and speeds of three fundamental kinds of seismic waves: Primary (P = pressure) waves; Secondary (S = shear); and Surface waves. A seismic wave is an elastic wave generated by an impulse such as an earthquake or an explosion. Seismic waves may travel either along or near the earth's surface (Rayleigh and Love waves) or through the earth's interior (P and S waves). (Recorded during a 2007 teacher workshop on earthquakes and tectonics. Speaker is Dr. Robert Butler, University of Portland Oregon)

Video Novice
Types of Seismic Wave Paths Through the Earth

Video lecture describing speeds and paths of different seismic waves within Earth from an earthquake to a distant seismic station. P & S waves travel through the Earth; Surface waves travel around the perimeter of the Earth.

Video Novice
Travel Time Curves Described
Dr. Robert Butler briefly describes how to use seismic travel-time curves. You can observe the P- and S-wave arrivals on a seismogram to calculate how far away an earthquake was from your station. A traveltime curve is a graph of arrival times, commonly P or S waves, recorded at different points as a function of distance from the seismic source. Seismic velocities within the earth can be computed from the slopes of the resulting curves.
Video Novice
Build a Better Wall Demo: Why Buildings Fail

The two most important variables affecting earthquake damage are (1) the intensity of ground shaking caused by the quake coupled with (2) the quality of the engineering of structures in the region. The level of shaking, in turn, is controlled by the proximity of the earthquake source to the affected region and the types of rocks that seismic waves pass through en route (particularly those at or near the ground surface).

 Generally, the bigger, closer, and shallower the earthquake, the stronger the shaking. But there have been large earthquakes with very little damage either because they caused little shaking in populated areas, or because the buildings were built to withstand that kind of shaking. In other cases, moderate earthquakes have caused significant damage either because the shaking was locally amplified, or more likely because the structures were poorly engineered.

 

Video Novice

Related Posters

This poster combines a visualization of ground motion resulting from the February 21, 2008 M 6.0 earthquake that occurred near Wells, NV, with the image of a faucet to illustrate a classic Earth science functional analogy: "Seismic waves radiate outward from an earthquake's epicenter like ripples on water".

Poster Novice

Seismic waves from earthquakes ricochet throughout Earth's interior and are recorded at geophysical observatories around the world. The paths of some of those seismic waves and the ground motion that they caused are used by seismologists to illuminate Earth's deep interior.

Poster Intermediate

Related Fact-Sheets

Earthquakes create seismic waves that travel through the Earth. By analyzing these seismic waves, seismologists can explore the Earth's deep interior. This fact sheet uses data from the 1994 magnitude 6.9 earthquake near Northridge, California to illustrate both this process and Earth's interior structure.

Fact-Sheet Novice

Knowing precisely where an earthquake occurred is an important piece of scientific information. It can help seismologists identify and map seismic hazards. It is also a fundamental piece of information necessary for facilitating studies of Earth's internal structures. This fact sheet provides an overview of the S-P process to locate an earthquake.

Fact-Sheet Novice

Earth is an active place and earthquakes are always happening somewhere. In fact, the National Earthquake Information Center locates about 12,000-14,000 earthquakes each year! This fact sheet illustrates information on the frequency of earthquakes of various magnitudes, along with details on the effects of earthquakes and the equivalent energy release.

Fact-Sheet Novice

Related Lessons

Learning occurs as students work first in small groups and then as a whole class to compare predicted seismic wave travel times, generated by students from a scaled Earth model, to observed seismic data from a recent earthquakes. This activity uses models, real data and emphasizes the process of science.

Lesson Novice

Through a demonstration lead by the teacher, the discrepant concept of rocks exhibiting elastic behavior is physically illustrated with an easily obtained, inexpensive model.

Lesson Novice

Silly Putty™ allows students to discover that the structure we see in rocks provides evidence for they type of stress that formed. Students apply this idea by examining images of faults and folds experimentation with sponge models.

The faults and folds in rocks provide evidence that the rocks are subjected to compressional, tensional, and/or shear stress.

Lesson Novice

The slinky is an effective tool for the demonstration seismic wave characteristics and wave propagation. Slinkys can be used both individually and in various combinations to demonstration different concepts.

Lesson Novice

Remember the “stadium wave,” when one person stands and raises his hands in the air and the motion is translated completely around the arena? This simple kinesthetic demonstration uses a similar principal by sending seismic waves through a line of people to illustrate the difference between P waves and S waves propogating through various materials.  Lined up shoulder-to-shoulder, students to "become" the material that P and S waves travel through so that once "performed," the principles of seismic waves will not be easily forgotten.

Lesson Novice

A candy bar, made almost entirely from nougat, is a useful model for connecting strain in rocks to faulting (earthquakes) and folding.

Lesson Novice

Learn about the earthquake magnitude scale and changes in the amount of energy released at each step by breaking different size bundles of uncooked spaghetti noodles! Students can both see and feel the differences in the energy released from a M4 - M8 quake. 

 

Lesson Novice

In this activity students will evalaute Silly Putty and Oobleck, both of which demonstrate proprieties of both solid and liquids, as a potential concrete model for Earth's Asthenosphere.

Lesson Novice

To understand plate tectonic processes and hazards, and to better understand where future earthquakes are likely to occur, it is important to locate earthquakes as they occur. In this activity students use three-component seismic data from recent earthquakes to locate a global earthquake.

Lesson Novice

Related Animations

In a normal fault, the block above the fault moves down relative to the block below the fault. This fault motion is caused by tensional forces and results in extension. Other names: normal-slip fault, tensional fault or gravity fault. Examples: Sierra Nevada/Owens Valley; Basin & Range faults.

Animation Novice

In a reverse fault, the block above the fault moves up relative to the block below the fault. This fault motion is caused by compressional forces and results in shortening. A reverse fault is called a thrust fault if the dip of the fault plane is small. Other names: thrust fault, reverse-slip fault or compressional fault]. Examples: Rocky Mountains, Himalayas.

Animation Novice

In a strike-slip fault, the movement of blocks along a fault is horizontal. The fault motion of a strike-slip fault is caused by shearing forces. Other names: transcurrent fault, lateral fault, tear fault or wrench fault. Examples: San Andreas Fault, California; Anatolian Fault, Turkey.

Animation Novice

An asperity is an area on a fault that is stuck or locked. Scientists study areas along long fault zones that have not had earthquakes in a long time in order to determine where the next earthquake may occur. As long faults move, all areas of it will, at some point, become "unstuck" causing an earthquake relative to the the size of the asperity that finally breaks.

Animation Novice

View looking into a fault zone with a single asperity. Regional right lateral strain puts stress on the fault zone. A single asperity resists movement of the green line which deforms before finally rupturing.

Animation Novice

Oblique-slip faulting suggests both dip-slip faulting and strike-slip faulting. It is caused by a combination of shearing and tension or compressional forces. Nearly all faults will have some component of both dip-slip (normal or reverse) and strike-slip, so defining a fault as oblique requires both dip and strike components to be measurable and significant.

Animation Novice

A transform fault is a type of strike-slip fault wherein the relative horizontal slip is accommodating the movement between two ocean ridges or other tectonic boundaries. They are connected on both ends to other faults.

Animation Novice

Animation shows the buildup of stress along the margin of two stuck plates that are trying to slide past one another. Stress and strain increase along the contact until the friction is overcome and rock breaks.

Animation Novice

The subduction zone iswhere two tectonic (lithospheric) plates come together, one subducting (diving) beneath the other. The plates are locked together and periodically overcome the friction causing the leading edge of the overlying plate to surge back, lifting a wall of water producting a tsunami.

Animation Novice

New oceanic crust is created at this boundary when basalt magma, formed in the mantle, rises into fractures in the crust and solidifies. Spreading ridges are high elevation because the young oceanic plate at the ridge crest is hot and less dense than the older, colder and more dense plate on the flanks of the ridge. 

Animation Novice

Oblique view of a highly generalized animation of a subduction zone where an oceanic plate is subducting beneath a continental plate. (See sketch below for parts.) This scenario can happen repeatedly on a 100-500 year cycle. The process which produces a mega-thrust earthquake would generate a tsunami, not depicted here.

Animation Novice

Stratigraphy is the branch of geology that studies rock layers; structure includes the faults and folds that result from regional & local forces acting on the area. A hypothetical cross section is studied by going back to the beginning to study its progressive geologic history.

Animation Novice

Seismic waves travel through the earth to a single seismic station. Scale and movement of the seismic station are greatly exaggerated to depict the relative motion recorded by the seismogram as P, S, and surface waves arrive.

Animation Novice

We use exaggerated motion of a building (seismic station) to show how the ground moves during an earthquake, and why it is important to measure seismic waves using 3 components: vertical, N-S, and E-W. Before showing an actual distant earthquake, we break down the three axes of movement to clarify the 3 seismograms. 

Animation Novice

A cow and a tree in this narrated cartoon for fun and to emphasize that seismic waves traveling away from an earthquake occur everywhere, not just at seismic stations A, B, C, and D. A person would feel a large earthquake only at station A near the epicenter. Stations B, C, D, and the cow are too far from the earthquake to feel the seismic waves though sensitive equipment records their arrival.

Animation Novice

This companion to the animation "Four-Station Seismograph network"  shows the arrival of seismic waves through select wave paths through the Earth (P and S waves) and over the surface of the Earth. The movement at distant stations occurs at a microscopic scale. While that doesn't result in noticeable movements of the buildings, the arrivals are recorded on sensitive seismometers.

Animation Novice

A gridded sphere is used to showt: 1) the seismic stations don't need to be lined up longitudinally to create travel-time curves, as they appear in the first animation, and 2) a single station records widely separated earthquakes that plot on the travel-time curves.

Animation Novice

A travel time curve is a graph of the time that it takes for seismic waves to travel from the epicenter of an earthquake to the hundreds of seismograph stations around the world. The arrival times of P, S, and Surface waves are shown to be predictable. This animates an IRIS poster linked to this animation.

Animation Novice

Seismic shadow zones have taught us much about the inside of the earth. This shows how P waves travel through solids and liquids, but S waves are stopped by the liquid outer core.

Animation Novice

The wave properties of light are used as an analogy to help us understand seismic-wave behavior.

Animation Novice

The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves. The different phases show how the initial P wave changes when encountering boundaries in the Earth.

Animation Novice

Graphing time vs. distance using the classic block-and-sandpaper "earthquake machine"

Animation Novice

Seismic tomography is an imaging technique that uses seismic waves generated by earthquakes and explosions to create computer-generated, three-dimensional images of Earth's interior. Human CAT scans are often used as an analogy. Here we simplify things and make an Earth of uniform density with a slow zone that we image as a magma chamber.

Animation Novice

The Earth has 3 main layers based on chemical composition: crust, mantle, and core. Other layers are defined by physical characteristics due to pressure and temperature changes. This animation tells how the layers were discovered, what the layers are, and a bit about how the crust differs from the tectonic (lithospheric) plates, a distinction confused by many.

Animation Novice

The "moment magnitude" scale has replaced the Richter scale for large earthquakes. Scientists have developed far-more sensitive seismometers that, with faster computers, have enabled them to record & interpret a broader spectrum of seismic signals than was possible in the 1930's, when the Richter magnitude was developed. Find out what scientists learn from seismograms.

Animation Novice

Related Videos

Video lecture about elastic rebound and brittle material in the crust using a yardstick as a mechanical analog. This demonstrates elasticity, brittle fracture, and why it is difficult to predict earthquakes.

Video Novice

The Earthquake Machine is a model of the earthquake process using a wood block, sandpaper, and rubber bands. This model shows how elastic energy is slowly stored as the rubber back stretches, and then rapidly releases the energy as the block jerks in an "earthquake".

Video Novice

Demonstration shows that rocks are elastic by squeezing a slit core of rock.

Video Novice

THE two-block "Earthquake Machine" uses two blocks with different grit sandpaper to model interactions between adjacent patches along a fault.

Video Intermediate

Conceptual model of the relative thicknesses of the Lithosphere relative to the diameter of the Earth uses a hard-boiled egg to gain understanding about the scale of the lithospheric plates.

Video Novice

Silly Putty is used as a model to show how the asthenosphere is elastic when exposed to short-duration forces (like seismic waves) but plastic when exposed to long-duration forces (like the load of the Hawaiian Islands on the Pacific Plate).

Video Novice

The arrival times of P and S waves are used to determine the distance to an earthquake using standard travel-time curves. 

Video Novice

Video lecture shows parts and tools needed to build an effective foam fault model. 

Video Novice

Demonstration by Dr. Robert Butler on how to design a structure to withstand shaking during an earthquake. This video walks you through the parts needed to construct the model, and shows you how to build it. 

Video Novice

How can I get across the idea in a classroom activity using no props?

The human wave is used as an analogy for travel times of P and S seismic waves.
This draft video uses arms over shoulders as well as hand holding methods, so read the caveats about the best method (arms over shoulders). 

Video Novice

Related Interactives

Roll over the buttons to see the difference between P- and S-wave seismic paths as well as their respective shadow zones.

Interactive Novice

Each station on the interactive map recorded an earthquake with a characteristic seismogram. Roll over the stations to see the epicenter triangulated. Touch buttons to watch movie of seismic waves, or touch "Walk-run" button to see wave travel can be demonstrated with a class.

Interactive Novice

Interactive map of tectonic plates from the US Geological Survey plate tectonic map reveals the plate names when you scroll over the plate. Scrolling over green button shows relative motions.

Interactive Novice

How are the tectonic plates related to earthquakes and volcanoes?

 Interactive relief and bathymetric map reveals tectonic plates, as well as world-wide earthquakes and volcanoes.

Interactive Novice

Related Software-Web-Apps

Seismic Waves is a browser-based tool to visualize the propagation of seismic waves from historic earthquakes through Earth’s interior and around its surface. Easy-to-use controls speed-up, slow-down, or reverse the wave propagation. By carefully examining these seismic wave fronts and their propagation, the Seismic Waves tool illustrates how earthquakes can provide evidence that allows us to infer Earth’s interior structure.

Software-Web-App Novice