Notes on Stress and Faults

          There are three different kinds of faults, and three different kinds of stress.  The different types can create mountains, valleys, earthquakes, tsunamis; a variety of different natural phenomena.  The different stresses can cause different faults, which change the physical features of the land.
          Stress is a force that squeezes or pulls crust rock.  It continually adds energy to the tectonic plates, and that energy is stored, and builds up, until the stone eventually breaks or changes shape.  Stress can work for over 1,000,000 years to change the shape of the original rock, and it either breaks brittle stone immediately, or bends them slowly.   There are three kinds of stress; tension, compression, and shearing.  Tension pulls apart the plates, making the rock in the middle thin.  It is caused by two plates moving apart.  Compression is when the tectonic plates are squeezed together, so that they either fold or break.  It is caused by one plate pushing the other.  Shearing is when two masses of rock slip in opposite directions.  This type of stress causes rock to either break and slip apart or change shape. 
          Faults are caused when too much stress builds up in a rock until it breaks.  Most faults occur along plate boundaries, where their forces either push or pull at the rock on the crust until it breaks.  The different types of faults are normal faults, reverse faults, and strike-slip faults.  A normal fault happens when tension pulls rocks apart.  The fault breaks at an angle, where one rock slides up, and the other goes down.  The rock that's higher up is called a "hanging wall," and the one below it has been dubbed "foot wall."  A reverse fault is caused when the earth's crust is pushed together through compression.  The reverse fault ends up basically the same way as a normal fault, it's just that the blocks move in opposite directions.  A strike-slip fault is caused by shearing tectonic plates.  Two rocks on either side of each other slip past each other sideways, without very much up-and-down motion.

Wave Stimulator Reflection

          While watching and experimenting with this wave stimulator, I noticed a couple different things. The higher the wave frequency, the lower the amplitude.  Even if you have the amplitude button as high as it will go, if you have a high frequency, the waves will not be very tall at all.  Instead, you will get a lot of waves, but with very low heights.  If you have a very, very low frequency level, but a super high amplitude, you will get one HUGE wave, and that's about it.  To get satisfactory large waves, you need to have a low frequency, though not necessarily a very low frequency level.  If you use two drops instead of one drop to create waves, they are, as can be expected, much larger, with higher amplitudes. 
When you add a barrier to the waves, they are divided into many smaller waves with less amplitude. 
          All in all, this website was very interesting, and I learned a lot about how waves work and how you can create higher amplitudes and wave frequencies by changing the sizes and speed of drops.  

Reflecting Waves Lab Report

Guiding Question: How do reflecting waves interact at different frequencies?

Hypothesis: I think that if we have a slower frequency of waves, hitting a surface straight on, we might get more standing waves, whereas if we have a higher frequency of waves, there might be destructive interferences.  If we create the waves at an angle, they will just reflect and move back in the opposite direction to which they got sent.

Exploration:

Materials:
Marker or Styrofoam Ball (1)
Plastic Tray (1)
Water (enough to fill tray)

Procedure:

1.) Dip the styrofoam ball or marker in the tray of water slowly, creating waves.  Make sure that you are not making the waves hit the other side of the tray at an angle - they need score direct hits.  Observe what happens.

2.) Keep creating waves in the same place as where you started, and increase the speed with which your dipping the styrofoam ball or marker.  Observe the reactions of the waves, and record.

3.) Move your hand so that you’re now creating waves to hit the plastic end of the tray at an angle.  Slow the wave frequency down.  Observe what happens.

4.) Keep your hand in the same place it is in now, and increase the wave frequency.  Observe what happens, and record.

5.) Complete all the other lab requirements after finishing this process.  

Table:

Hitting Angle:	Straight	Straight	Angle	Angle
Frequency:	High	Low	High	Low
Reaction:	-Waves are larger -Waves expand to hit all surfaces of tray -All waves bounce back, but not conspicuously -Waves aren’t completely circular (like round squares)	-Waves are not as distinct -Waves expand to hit all surfaces of tray -Waves bounce back more visibly -Waves bouncing back are very light.	-From early on, waves spread out in flower form (3 petals) -Waves hit surfaces + bounce back multiple times -Creates plaid-like surface -Never reaches far corner of tray	-Waves are circular, followed by petals -Waves gradually fade -Waves hit surface + bounce back, but they are barely visible

Analysis of Data:  I noticed that in all circumstances, the waves hit the edge of the tray with enough energy to bounce back.  In almost all cases, the waves bouncing back were not easily visible when bouncing back, but they did, all the same.  In many cases, the waves either spread out to hit all the edges of the tray, or they take on some strange shape - flower petals, rounded rectangles, regular waves followed by flowers... When I made the waves hit the tray at a straight angle, they were more likely to visibly expand better.  When I made the waves hit the edges at angles, they did expand, but not as well.

Conclusion: I think that reflecting waves interact in basically the same way even at different frequencies and angles.  Waves reflecting at a high frequency bounce off the edge of the tray and overlap, creating standing and destructive waves.  My hypothesis was incorrect, because at both frequencies, destructive waves were created, slowing down the ones that had collided.  I still don’t really understand why this happens, but I do understand that it does happen.

Further Inquiry:  The major causes of error occurring in my experiment could have been that my eyes weren’t sharp enough.  I might have thought I saw a destructive interference, when really it was something completely different.  To prevent this from happening, I could take a video of it next time, and watch the tape multiple times in slow motion to really understand what is happening in my tray, and attempt to find more patterns.  Some more questions I could ask could be, “What happens when waves reflect through deeper and shallower water,” or “How do waves reflect in smaller spaces?”

What Happens when a Wave Hits a Surface

Process:
          What we did to learn about how waves react when they hit a surface was to use differently shaped spheres as our waves.  We rolled the balls at a wall, and followed their paths with marker.  To conduct this experiment, we used styrofoam spheres, a small, pink, plastic ball, a marble, a big marble, a ping pong ball, and a golf ball.
          The small marbles never even made it to the wall.  They curved to the right before they could touch it.  The pink plastic ball hit the wall and came almost straight back down.  The big marble hit the wall at an angle and came back down the opposite way, forming a triangle-like shape.  The ping pong ball made another point, and the golf ball made one twice on each trial.  Lastly, the styrofoam ball hit the wall and came straight back down.
         
Conclusion:
          I think that the results of our experiments mean that waves/spheres will bounce off any surface they hit, and go in the direction of the angle opposite to the one they hit the wall at, creating peaks.  If the wave hits the barrier straight on, then it will come straight back.  If it hits it going this way: /, it will come back this way: \, and vice-versa.  This is called reflection.  It makes sense, because if there was an imaginary mirror reflecting the wave, it would look like a reflection! That is basically what a wave does when it hits a surface.

Reflection - How do waves interact in a tub of water?

1.) No Barriers:
          I think that waves interact best without any barriers.  I noticed that when our blocks of clay were absent, the waves were able to overlap and slow each other down.  Barriers obstruct the movement of waves, and therefore prevents them from interacting.  Without that obstruction, waves are free to interact without being hindered.

No Barriers

2.) One Barrier:
          It depends on where the barrier and the points of energy where the waves are formed are placed, but in most cases, the waves end up interacting all right.  The farther the wave gets away from its energy source, the wider it becomes, so once it reaches the barrier, the wave is too wide to be completely stopped by it, and goes around the obstruction without much trouble.  This is called diffraction, because it is bending and then broadening again after passing the barrier.

One Barrier

3.) Two Barriers:
           When you have both barriers protruding out from the sides of the plastic container, just leaving a small space for the waves to interact between them, the waves don't usually meet.  They will spread out as far as the barriers allow them, but will leave the space between the two untouched.  According to our observations, the water between the two obstructions hardly moves at all.  Although they aren't able to go through/around the barriers, the waves do bounce back, and they cause standing waves, which look like they're staying still, when really both waves are moving in the opposite directions.

          As you can see in each of the pictures on this blog post, they are parts of my notebook sketches of the different ways the waves interacted with the barriers.

Two Barriers