Shake, Rattle, and Roll
(based on an acitivity at http://ravensweb.150m.com/APES/Classwork/earthquake.htm)
Shake It Up Baby! Twist & Shout!
The Dynamics of Plate Tectonics: Earthquakes, Volcanoes, & Change
(http://www.pbs.org/wnet/savageearth/)
(http://cse.ssl.berkeley.edu/lessons/indiv/davis/hs/reading.html)
(http://wps.prenhall.com/esm_thurman_introocean_9/0,7305,348130-,00.html)
(http://www.ucmp.berkeley.edu/geology/anim1.html)
Plate Tectonics
The theory of plate tectonics indicates that earth's surface sits on a large floating island
of rock. Although it feels solid and hard beneath our feet, the outer surface of the Earth
is a thin crust of fragile rock, fractured like the cracked shell of an egg. The pieces of the
shell are Earth's tectonic plates -- there are 12 major ones -- and they float across a
layer of soft rock like rafts in a stream, their motions driven by forces generated deep in
the Earth. At their boundaries, the plates spread apart, converge, and slide past one
another. Access the following link to read and observe the most common plate
boundaries that occur as a result of tectonic plate theory. Then, access the link below it
to experiment with the phenomena.
Savage Earth Plate Boundaries Descriptions
Savage Earth Plate Boundaries Applications
As you proceed, answer all items in your lab notebook. Answer items 1 & 2 below.
Earthquakes & Seismograms
Most earthquakes happen near the boundaries of tectonic plates, both where the plates
spread apart and where they crunch or grind together (although large temblors also
strike from time to time in the normally stable interior of continents). Along plate
boundaries, the brittle outer part of the Earth fractures along faults. As plates move,
blocks of crust shift along the faults. The infamous San Andreas fault is not a single
crack where the North American and Pacific plates slide past each other. It's the largest
of a thicket of faults that collectively absorb the motion of the plates.
A typical earthquake sends out at least three types of waves. These waves travel
differently in the earth and make different patterns on the seismogram, a read-out from
a sensitive detecting instrument called a seisometer measuring tectonic activity. These
are quite useful in detecting the epicenter or the location on the surface of the earth
directly above the focus of an earthquake.
Following an earthquake, the body waves strike first. The fastest kind are the primary
waves, or P-waves. People often report a sound like a train just before they feel a
quake, which is the P-wave moving as an acoustic wave in the air. Then the secondary,
or S-waves, arrive. A person in a building perceives the arrival of S-waves as a sudden
powerful jolt, as if a giant has pounded his fist down on the roof. Finally, the surface
waves strike. In very strong earthquakes, the up-and-down and back-and-forth motions
caused by surface waves can make the ground appear to roll like the surface of the
ocean, and can literally topple buildings over. The L-waves or surface waves usually
cause the most damage.
Primary Waves (P)
Secondary Waves (S)
Surface Waves (L)
Look carefully over the eight seismograms from the seismic stations around the world at
the following link:
Seismograms from a Recent Earthquake
Answer items 3-18 below.
Volcanic Eruptions & Weather/Climate Change
Though environmental scientists argue that global warming is a real phenomena
causing significant reaching effects on a variety of global systems, outspoken skeptics
argue that climate change is a fabrication and fallacy. Media personality Rush
Limbaugh has repeatedly asserted his opinion that "natural phenomena such as
volcanic eruptions emit pollutants in volumes that dwarf those produced by human
activity, thus proving that fears of global climate change are fabricated."
More than 80 percent of the Earth's surface -- above and below sea level -- is of
volcanic origin. Gas emissions from volcanic vents over hundreds of millions of years
formed the Earth's earliest oceans and atmosphere, which supplied the ingredients vital
to evolve and sustain life. Over geologic eons, countless volcanic eruptions have
produced mountains, plateaus, and plains, which subsequent erosion and weathering
have sculpted into majestic landscapes and formed fertile soils. But, although there are
hundreds of active volcanoes worldwide, most erupt only intermittently. A few erupt
often, such as Hawaii's Mauna Loa, but most erupt only once every few decades to
once in several centuries. A few massive eruptions have occurred during the past
several thousand years, e.g., Mt. Mazama in Oregon, whose remains make up Crater
Lake National Park. And once every few hundred thousand years, a truly gigantic
eruption occurs, producing deposits such as California's Bishop Tuff and having
profound local and regional effects on climate and life.
Within the past few centuries, several volcanic eruptions have had well-documented
temporary effects on terrestrial climate. One such event occurred in the late 1880's, the
eruption of Krakatau in what is presently Indonesia. Such eruptions are so powerful that
they blast vast quantities off ash and gas into the stratosphere (upper atmosphere)
above the zone of atmospheric turbulence. This ash and gas layer stays in the
atmosphere for up to several years and is distributed globally by prevailing high-altitude
winds. The ash and gas reflect the solar radiant energy back to space before it can
reach the lower atmosphere or the planet's surface, thus resulting in cooling the Earth
called the albedo effect. This cooling may last, as in the case of the eruption of Mt.
Pinatubo in 1991, for several years. In 1815, the volcano Tambura erupted in the East
Indies, producing the so-called "year without a summer" in parts of the Northern
Hemisphere such as New England, where snow fell in July, and much of western
Europe, where crops failed.
Do volcanic eruptions have long-term effects? Pinatubo's eruptive volume was
estimated at 9 billion cubic yards (yd3). We will study the effects of the eruption in 1991
to determine if it played a role in changing weather patterns or inspiring global climate
change.
Some Useful Conversions:
1 yd3 = 0.76 m3
1 ton = 2000 lb
1 metric ton (tonne) = 1000 kg = 2200 lbs
1 kg = 1000 g = 2.2 lb
454 g = 1 lb
Answer items 19-23 below.
Continental Drift and Plate Tectonics
In 1912, Alfred Wegener proposed that continental drift has provided a mechanism for
the diversification of life on the planet and provides an explanation for the similarities
between species on continents completely separated by oceans. According to the
theory of plate tectonics, large plates under the Earth's surface drifted away from one
another at a rate of 2cm/year and are still moving away from one another. The original
supercontinent, Pangaea, gradually broke apart into pieces as the plates drifted, caused
by degassing of the Earth's hot magma interior. The movement of plates has led to the
further understanding of speciation and biogeography, the geographical distribution of
flora and fauna. Support for Wegener's hypothesis is found in the location of marsupials
(ex/ kangaroos) as far away from Australia as the United States (ex/ opossum). As well,
lungfishes are found in three continents suggested that they rose from a common
ancestor on Pangaea.
Continental Drift Timeline:
Era
Time
(mya)
Action
Result
Paleozoic 543
Pangaea is a single
continent.
Migration and movement of species
between temperate & tropical climates.
Mesozoic 180
Pangaea begins to
separate
Gondwanaland (south) and Laurasia (north)
Cenozoic 65
Modern continents
begin to separate
Formation of 5 continents; Australia
continues to move south.
1. What is tectonic plate theory?
2. Identify and describe the major types of plate boundaries indicating causes and
effects?
3. Which location experienced the greatest shock? How can you tell?
4. Which location is probably closest to the epicenter?
5. Which location is the farthest from the epicenter?
6. Name the four locations on the seismogram that received all three types of
waves (P, S, and L) and identify the times each of the three waves arrived.
7. Which type of wave is the fastest?
8. Which type of wave is the slowest?
9. At which location did the P and S waves arrive closer together -- San Francisco
or Hawaii? What does this tell you about the location of the epicenter?
10. At some locations, not all of the three waves arrived. Which locations appear to
have received only P and L waves, but no S waves?
11. Which locations appear to have received only L waves?
12. Did San Francisco receive a P wave? did Los Angeles?
13. Compared to the size of the earth, these two cities are close to each other. Why
do you think the P wave arrived in one of these cities but not in the other? Make
a good hypothesis to explain this observation.
14. Look at the L waves for Kingston, for Jamaica and for Miami, Florida. Which Lwave -- Kingston or Miami -- is probably closer to the epicenter? How can you
tell from the seismograms?
15. Did Kingston receive a P wave? did Miami receive a P wave?
16. These two cities are not very far from each other on the earth. Why did the P
wave arrive in one of these cities but not in the other? Make a good hypothesis
again.
17. A good average for Mt. Pinatubo's eruptive density is 2000 kg/m3, consisting of
ash, pumice, and some basalts. How much did the entire eruptive mass weigh?
18. If 1% of this mass was gas, what was the mass of the gas within the eruptive
material?
19. The U.S. Geological Survey estimates CO2 content at 15% of the total gas mass,
84% was water vapor, and 1% was trace gases such as heavy metals. What is
the approximate weight of CO2 from the Mt. Pinatubo eruption?
20. The total anthropogenic (human-produced) CO2 is approximately 7700 million
tons per year. What percentage of this number is the calculated CO2 content of
the Mt. Pinatubo eruption? How many Mt. Pinatubos would have to erupt to
produce 10% of the total annual anthropogenic CO2? On the basis of these
calculations, do you conclude that volcanic eruptions dwarf human sources of
CO2? Likewise, do they create long-term climatic changes?
21. Access this link and determine if volcanoes can have short-term effects upon
weather patterns. Use information from at least two case studies to support your
hypotheses.
22. According to the data provided and estimates for the reate of separation, how far
had Gondwanaland and Laurasia separated before they each began to break
apart?
23. How wide should the Atlantic Ocean be at its WIDEST point?
24. If the Atlantic Ocean is estimated to be 2.575 km wide at its widest point
according to modern cartographic data, how has the rate of continental drift
changed?
25. Explore the animation below to identify several species that evolved during each
or the primary eras described above. Then view the animation at the second link
below to help you visualize how the geology of the surface of Earth changed
during specific time periods. Ude this information to explain how continental drift
may have contributed to the specific diversity or change that defined each
species.
Deep Time & Speciation
Continental Drift Animation
(Clicking Refresh will replay the animation.)