1.)a.)The density range of the earth is approximately: 2.7 - 13 g/cm3 20 - 32 g/
ID: 637416 • Letter: 1
Question
1.)a.)The density range of the earth is approximately:
2.7 - 13 g/cm3
20 - 32 g/cm3
30 - 125 g/cm3
3.3 - 8 g/cm3
70 - 2900 g/cm3
b.) Where do pillow basalts form?
in the core
on the abyssal plain
along the mid-ocean ridge
in ocean trenches
c.) Island arcs of volcanoes, such as Japan and the Philippines, are characteristic of a:
ocean-continental convergent boundary
ocean-ocean convergent boundary
ocean-ocean divergent boundary
continental-continental divergent boundary
hot spot
d.) We have drilled into the mantle, but not into the core.
True
False
e.) What is the maximum depth of the ocean at the deepest ocean trench:
0.5 km
1 km
11 km
100 km
5 km
Explanation / Answer
a) The density range of the earth is approximately:
Ans. 2.7 - 13 g/cm3. This is the range of density of earth. Below is the breakup of this density.
Crust – 2.2 to 2.9 g/cm3
Upper Mantle – 3.4 to 4.4 g/cm3
Lower Mantle – 4.4 to 5.6 g/cm3
Outer core – 9.9 to 12.2 g/cm3
Inner core – 12.8 to 13.1 g/cm3
b) Where do pillow basalts form?
Ans. Along the mid-ocean ridge – Mid-ocean ridges are seismically active regions in the middle of the oceanic basin. Pillow Basalts are formed when lava erupts underwater and the contact between the molten lava and the cool water results in rapid cooling of the outer skin of the lava while it is being elongated by more molten lava coming from underneath, giving it a pillow like shape.
c) Island arcs of volcanoes, such as Japan and the Philippines, are characteristic of?
Ans. ocean-ocean convergent boundary – This is where two oceanic plates collide into each other. The older one, since it is denser, subducts beneath the younger oceanic plate and melts as it is pushed deeper into the mantle. The magma, thus created, rises, erupts and forms a line of volcanoes; which is what we call island arcs.
d) We have drilled into the mantle, but not into the core.
Ans. False – we have drilled kilometres into the crust but are yet to drill into the mantle.
e) What is the maximum depth of the ocean at the deepest ocean trench?
Ans. 11 km – The deepest point in the earth’s oceans has been measured at 11 kilometres (10994 metres approx) below sea level. This point is called The Challenger Deep which is present in the Mariana Trench of the North Pacific Ocean.
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