Plate Tectonics /Earthquakes Test Review
Answer questions on a separate sheet of paper. Practice sheets for #1 available.
1. Given the lag time between three sets of P and S waves, a time travel chart, a map,
and a compass, find the epicenter of an Earthquake.
Students were provided with practice materials. 1. Calculate time between arrival of
P wave and S wave. 2. Find the time lag on the y axis of the time travel chart, and
mark it on an index card. 3. Slide the card to the right until the height of the line
reaches the distance between the P curve and the S curve on the chart. 4. Look at the
x axis to determine the distance. 5. Create a circle around the origin that extends the
distance found for the location. Repeat for 2 more locations. Epicenter is the point
where three circles intersect.
2. What is the difference between EQ Magnitude and Intensity, and what are the scales
for each?
Magnitude refers to the energy released at the moment of slippage, Intensity refers to
the damage caused by an Earthquake. The Intensity is measured on the Modified
Mercalli scale and can differ based on the distance from the epicenter. The
Magnitude is measured on the Moment Magnitude scale.
3. What is the difference between the Moment Magnitude scale and the Richter scale?
Which is more current and accurate?
The Richter scale is an older, now outdated method of measuring EQ magnitude,
based on the height of the waves on a seismogram. Moment magnitude is the current
scale used to measure EQ magnitude, based on seismograms and a number of other
factors including area of rock that moved, distance of displacement, and the strength
of the rock.
4. Who first looked for scientific evidence to support the idea that the continents once fit
together? Alfred Wegener
5. What evidence did this person find, and why was it not enough to convince the
scientific community?
Evidence included 1) Rock formations on the coast of S.America and N. America that
matched the age and type of rock on the coast of Africa and in the British Isles. 2)
Fossils that matched organisms living in S. America and Africa, and Australia that could
not have travelled across large expanses of ocean. Glosspetris, a plant, and
Mesosaurus, a fresh water reptile. 3) Telltale signs of glacier motion on bedrock in
Africa, Australia, and S. America that could not have formed if the continents were not
connected, because glaciers do not form on water then move onto land.
6. Describe at least one type of technology that was developed during the cold war that
helped lead to the development of the Theory of Plate Tectonics.
1) The development of more sensitive equipment to detect earthquakes came from
technology that scientists developed to monitor the testing of nuclear weapons by
the Soviet Union.
2) The development of technology using magnets to detect soviet submarines
resulted in the surprise discovery that the ocean floor stores the record of
magnetic polarity reversals. PALEOMAGNETISM
7. How many major tectonic plates are there? 15
8. What are the three classifications of plate boundaries?
Divergent, Convergent, and Transform
9. What is a transform boundary, and give an example. The San Andreas Fault is a
Transform boundary. Two plates meet, neither subducts, but they slide past each
other.
10. Give one example each for the two different types of divergent boundaries.
Seafloor Spreading – The MidAtlantic Ridge
Continental Rifting – East Africa Rift Valley
Essay:
Describe what happens at each of the convergent boundaries below. Tell which plate
subducts and why, and what geologic activity occurs. Correctly include the terms island arc,
volcanic arc, earthquake/s, and mountain building. Give one example of each plate
boundary.
Continental – Continental
The Himalayas where India meets the Eurasian plate is an example of Continental –
Continentaly convergence. Neither plate subducts, and mountain building occurs.
Oceanic – Continental
The Juan De Fuca plate is an Oceanic plate that is subducting under the N American plate. In
an oceanic-continental convergence, the oceanic plate will subduct because it is denser.
Volcanic arcs form on the continent, and earthquakes also occur.
Oceanic- Oceanic
When two oceanic plates collide, the older will subduct because the older ones are denser.
At oceanic –oceanic convergences, island arcs form. An example of this is the Phillipine
Islands ore the Aleutian islands.
You will be able to use your reference table of the tectonic plates for this exam.
STUDY JAM:
There will be a study party on Friday after school in McN 7. Students who have scored lower
than a B on any major test this year are strongly encouraged to attend! Snacks will be
provided!