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Winter 2007: Ocean 115
Class-Test 1A
GLENDALE
COMMUNITY
COLLEGE
Answer question items 1-30 on the
scantron sheet as contextually relevant
True/False propositions and Part III as
short descriptive notes.
Oceanography
Dr. Poorna Pal
Part I: Each question-item below, 1 through 10, is either TRUE or FALSE.
1. A marine magnetic profile such as the one
alongside suggests that the basaltic ocean floor
has alternate bands of ‘normal’ and ‘reversed’
magnetization.
2. Hydrological cycle is the continuous circulation of water between atmosphere and the Earth.
3. Lithosphere is the Earth’s rigid outermost shell, with an average density of 2.75 gm/cm3, that is
30-35 km thick beneath the continents where it mostly comprises granites.
4. Of the two views of the globe alongside, the one on the left
is that of the Pacific Ocean.
5. The oldest ocean floor rocks are found to be less than 200
million years in age.
6. Glendale’s latitude of 34.17˚N means that it is located south
of the Tropic of Cancer.
7. Earthquakes typically characterize the plate boundaries,
except that a spreading submarine ridge like the East Pacific Rise has seismicity even though it
is not a plate boundary.
8. Mariana Trench, the deepest point on Earth’s surface, formed by convergent tectonism
involving the continental edge of one plate and oceanic edge of another.
9. Mid-Atlantic Ridge is located in the middle of the Atlantic Ocean because it was produced by
seafloor spread whereas East Pacific Rise is located towards the eastern Pacific, apparently
because it did not evolve by way of any seafloor spread.
10. Abyssal sea floor is generally the deepest part of the ocean floor.
Part II: Answer question-items 11-30 below as contextually relevant True/False propositions.
A. This map of earthquake epicenters worldwide
suggests that …
11. abyssal seafloor is the World ocean’s largest
physiographic province.
12. abyssal seafloor, World ocean’s largest physiographic province, generally lacks seismicity.
13. all spreading submarine ridges have seismicity.
B. Looking at the data tabulated on the left, could we
argue that …
14. Earth’s total surface area is ~510 million km2?
15. Pacific ocean covers ~50% of Earth’s surface?
16. the average seafloor is ~4 km in depth?
Surface Area (million Km2)
Pacific Ocean 165.2
Atlantic Ocean 82.4
Indian Ocean 73.4
C. Mt. Annapoorna, the Himalayan peak pictured on the
right, comprises limestones with ~200 Ma old ammonite
fossils. This suggests that …
17. an ocean covered the present site of Himalayas about
200 million years ago.
18. limestones form on high mountain peaks and deep sea
floor
19. Indian subcontinent was once located about 5000 km to
the south, adjacent to Africa.
Other waters 40.0
All the waters 361.0
all land area 148.0
Height or Depth (Km) relative to MSL
D.
Looking at the graph alongside, can we say that …
8
0.5%
1.1%
4
20.
21.
2.2%
4.5%
0
3.1%
6.0%
-4
0%
14.9%
22.
22.5%
15.0%
0.9%
0.05%
-8
20.8%
8.5%
10%
20%
Proportion of Earth’s Surface
oceans cover ~70% of the Earth’s surface?
over one-half of the Earth’s surface lies 3-6 km below the
mean sea level (MSL)?
deep sea trenches,
the deepest and the
darkest part of the
ocean, cover
1-1.5% of the
Earth’s surface, at
the most?
E. Does this map on the right show …
23.
24.
the deep sea trenches such as the Mariana trench
and the Java trench?
a spreading submarine ridge like the Mid-Atlantic
ridge?
F. Venus is located at ~0.7 AU (astronomical unit = mean
Earth-Sun distance) but the surface of that planet
receives the same amount of Solar heat per unit area as
the Earth. Why?
25.
26.
27.
G.
As the surface of Venus is very hot, more Solar heat clearly reaches the surface of Venus,
per unit area, than what reaches the Earth’s surface.
The surface of Venus is too hot to allow the existence of any hydrological cycle on Venus.
The atmosphere of Venus filters ~75% of the Solar heat reaching that location whereas
the much thinner atmosphere of Earth filters roughly one-half of Solar heat that reaches
Earth’s surface.
The reconstruction of landmasses ~200 Ma ago, shown
alongside, was first proposed by Alfred
28.
29.
30.
Part III:
oceans cover over two-thirds of the Earth’s surface and
have an average depth of ~4 km below the sea level
surface.
the relative geography of oceans and continents on
Earth has changed over the geologic time.
Central Atlantic, produced by the separation of North
America from Africa, clearly formed well before the
formation of the South Atlantic.
rth
No ica
r
e
Am
So
Am uth
er
ic
a
Eurasia
Af r
ica
India
Au s
a
trali
Antarctica
Write short descriptive notes (50-75 words each) on ANY TWO of the
following (feel free to add line drawings and/or conceptual diagrams).
15 points
each
(a) What is hydrological cycle? Why do we say that, had it not been for plate tectonics, the
hydrological cycle on Earth would have disappeared in a matter of ~200 Ma.
(b) What would be the possible reason (or reasons) why Mars lacks the kind of abundance
of water that the Earth has? Explain.
(c) How does spreading at the submarine ridges create the new ocean floor? Does it explain
why the ocean floor is basaltic?
(d) Do deep sea trenches form at divergent or convergent plate boundaries? Explain what
kinds of plate interactions produce them. Give suitable examples.