Geodynamics Quiz 2: plate motions, con’t
Read Chapter 2 from section 2.4.1 to the end of the chapter (peruse section
2.4.2, we’ll go over this in more detail in lab)
1 Since the earth is actually not flat, we have to think about plate motions on a spherical earth, using
angular velocities. The symbol for angular velocity is ________, and clockwise motion (as viewed from
the center of the earth) is ____________
a) ω, negative
b) V, positive
c) ω, positive
d) V, negative
2 When plates move on a spherical earth, they are actually rotating about an Euler Pole. The Euler Pole
e) Is the “imaginary pole”, or point on the surface of the earth, that the plate is rotating around
f) may be located within the plate, or outside of the plate
g) can be found by looking at the alignment of transform faults connected to spreading ridges
h) is the pole that the firemen use at the fire station
i) e, f, and g are all true
3 On a spherical earth, the relative velocity between two plates at a point (X) is
v=ωRsinΘ
where Θ is the angular distance from the Euler pole to the
point X. Thus, the closer you get to the Euler pole (the smaller Θ is), the
relative velocity becomes
j) Faster
k) Slower
l) The same
m) approaching the speed of light
4 Once you determine the spreading rate at various locations along a ridge, you can use the equation
v=ωRsinΘ
το
n) estimate the angular velocity
o) estimate the location of the Euler pole
p) do both n and o
q)
5 just like we use vector addition on the flat earth to determine relative plate velocities, we can use
vector addition on the spherical earth. The equation we use is:
a) BϖC=CϖA + AϖB
b) CϖB=CϖA + AϖB
c) BϖC=AϖC + AϖB
d) BϖC=AϖB + BϖC
Imagine you live in a house at the “T” on plate A, and your Professor lives in a house on plate C, in the circle
near the boundary with Plate A.
6 What will happen to your house:
r) Nothing
s) It will eventually go down the subduction zone
t) It will always stay above the subduction zone
u) It will move north relative to plate C
v) Both s and u are true
7 What will happen to your Professor’s house?
w) It will continue to slide south relative to plate A
x) It will eventually go down the subduction zone
y) It will always stay above the subduction zone
z) It will eventually be next to plate B
aa) Both w and z are true
8 A triple junction:
bb) Is An awesome bar in Mendocino
cc) Is A location where three plates meet
dd) May be unstable
ee) Both aa and bb are true
9 The triple junction shown ----------------------------------------------- over here
is unstable because
ff) The geometry of the triple junction does not change with time
gg) The geometry of the triple junction will be different in the future
hh) The relative velocities between the plates will be different in the future
ii) All of the above are true
10 it is difficult to determine absolute plate motion (vs relative) because
jj) we need a frame of reference that is fixed
kk) all spots on the surface of the earth are moving
ll) absolute vodka is hard to find
mm) hh and ii are true