Tuesday, 26 February 2019

Earth Science Olympiad - Previous Questions 6

Earth Science Olympiad - Previous Questions 6

1. It is observed in the field that a limestone is intruded by a dolerite dyke. A volcanic flow overlies the limestone. Which of the following statements is more likely to be true?
Limestone is chemically precipitated simultaneous to an underwater volcanic eruption that emplaced dolerite dyke and volcanic flow
Limestone is the oldest rock of the three while the volcanic flow is the youngest
dolerite dyke and volcanic flow occurred simultaneously prior to the limestone deposition
Dolerite dyke is the youngest rock while the volcanic flow is the oldest.

2. Elevation of Earth’s crust is bi-modal on an average- continents being above sea-level and oceanic crust is below sea level. This is because:
There are mountains on the continents, while there are no such high elevation regions on oceans
Oceanic crust is denser while the continental crust is lighter
oceanic crust has depressions caused by meteorite impacts during the early history of the Earth
oceans are formed by melting of continental glacial

3. The mantle convection is caused by
Plate movements
rotation of the Earth
temperature and density difference
upwelling of pressurized liquid mantle

4. Magmatism takes place at divergent plate boundary because of
Decompression of mantle below the diverging plates
percolation of sea-water into the mantle
frictional heat during divergence of plates
generation of mantle plume

5. Which of the following layers inside the Earth is dominantly liquid?
Upper mantle
Lower mantle
Outer core
Inner core

6. The density of materials inside the Earth
Increases with increase in depth
decreases with increase in depth
is maximum in mantle
remains unchanged with depth

7. A given mass weighs slightly different at pole and equator of the Earth. This is because of
the combined effect of Earth’s oblate shape and its rotation, gravity is slightly more at equator than at pole resulting in higher weight at equator
the combined effect of Earth’s oblate shape and its rotation, gravity is slightly less at equator than at pole resulting in lower weight at equator
the presence of polar ice of lower density, gravity is less at pole resulting in lower weight at poles
the convergence of magnetic lines at poles, the weight is measured more at pole.

8. Which of the following minerals is not a silicate?

9. Cations such as Mgand Fereplace each other in certain minerals like olivine and pyroxene. It is possible because of
change in chemical composition in the surrounding environment of these minerals
similar charge and size of these cations
these minerals lack a fixed crystal structure
larger abundance of these elements in these minerals

10. Two different primary igneous rocks undergo metamorphism at same pressure and temperature. Both these rocks, subsequent to metamorphism would have
Identical mineral assemblage reflecting the metamorphic facies characteristic to that pressure and temperature
different mineral assemblage because of difference in their bulk chemical composition
no change in their mineral assemblage but their bulk chemical composition would have changed
identical bulk composition but different mineral assemblage

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