8th Grade: What Do You Know About Earth Science?
The countryside around us, including the built environment, is often influenced by what lies underneath our feet - the rocks. Rocks form the Earth's crust and belong to one of three main groups - sedimentary, igneous and metamorphic. Their formation is linked by the rock cycle.
- 1.
Which of the following statements is incorrect?
- A.
Igneous rocks are made from grains of other rocks that have been cemented together
- B.
Sedimentary rocks normally form in layers
- C.
Both metamorphic and sedimentary rocks can contain visible layers
- D.
Igneous and metamorphic rocks often contain crystals
Correct Answer
A. Igneous rocks are made from grains of other rocks that have been cemented togetherExplanation
Igneous rocks are not made from grains of other rocks that have been cemented together. Igneous rocks are formed from the solidification of molten material, such as lava or magma. This process results in the formation of interlocking crystals, rather than grains of other rocks.Rate this question:
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- 2.
Which of the following is the correct sequence that describes the formation of a sedimentary rock?
- A.
Suspension, deposition, compaction, cementation
- B.
Sedimentation, deposition, cementation, compaction
- C.
Suspension, compaction, cementation, deposition
- D.
Deposition, cementation, sedimentation, suspension
Correct Answer
A. Suspension, deposition, compaction, cementationExplanation
The correct sequence that describes the formation of a sedimentary rock is suspension, deposition, compaction, cementation. Suspension refers to the process of particles being carried by water or wind. Deposition occurs when these particles settle and accumulate. Compaction is the process of the accumulated particles being compressed due to the weight of overlying layers. Cementation is the final step where minerals dissolved in water fill the spaces between particles, binding them together to form a solid rock.Rate this question:
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- 3.
Which of the following statements is NOT true?
- A.
Sedimentary rocks are usually formed under water
- B.
Metamorphic rocks have been melted
- C.
Igneous rocks are often associated with volcanoes
- D.
Metamorphic rocks can be made from igneous, sedimentary or other metamorphic rocks
Correct Answer
B. Metamorphic rocks have been meltedExplanation
Metamorphic rocks have not been melted. Instead, they are formed through the process of heat and pressure acting on existing rocks, causing them to change their form and structure. This process occurs deep within the Earth's crust, where the temperature and pressure are high enough to alter the minerals and textures of the rocks without melting them completely. Therefore, the statement that metamorphic rocks have been melted is not true.Rate this question:
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- 4.
Which type of rock is made from molten magma that has cooled down and solidified?
- A.
Igneous
- B.
Metamorphic
- C.
Sedimentary
- D.
All three
Correct Answer
A. IgneousExplanation
Igneous rocks are formed from molten magma that has cooled down and solidified. Magma is molten rock that is found beneath the Earth's surface, and when it cools and solidifies, it forms igneous rocks. These rocks can have a variety of textures and compositions, depending on the cooling rate and the minerals present in the magma. Examples of igneous rocks include granite, basalt, and obsidian.Rate this question:
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- 5.
In a sequence of sedimentary rock layers, where would you find the most recently formed rock?
- A.
It would be the lowest layer
- B.
It would be the middle layer
- C.
It would be the topmost layer
- D.
It is impossible to tell without carbon dating the rocks
Correct Answer
C. It would be the topmost layerExplanation
In a sequence of sedimentary rock layers, the most recently formed rock would be found in the topmost layer. This is because sedimentary rocks are formed over time as layers of sediment accumulate on top of each other. The oldest layers are at the bottom, while the youngest layers are on top. Therefore, the topmost layer would be the most recently formed rock.Rate this question:
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- 6.
At which type of plate boundaries are you most likely to find igneous rocks forming?
- A.
Conservative and destructive
- B.
Destructive and constructive
- C.
Constructive and conservative
- D.
They will form at all three types of plate boundary
Correct Answer
B. Destructive and constructiveExplanation
Igneous rocks are formed through the solidification of molten magma or lava. At destructive plate boundaries, where one plate is being subducted beneath another, magma is often generated as the subducting plate melts. This magma can then rise to the surface and solidify, forming igneous rocks. Similarly, at constructive plate boundaries, where two plates are moving apart, magma can also be generated through the partial melting of the asthenosphere. This magma can then rise to the surface and solidify, forming igneous rocks. Therefore, igneous rocks are most likely to form at both destructive and constructive plate boundaries.Rate this question:
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- 7.
Which word describes an ingneous rock that is formed deep within the crust of the Earth?
- A.
Extrusive
- B.
Intrusive
- C.
Extra-terrestrial
- D.
Intra-terrestrial
Correct Answer
B. IntrusiveExplanation
An intrusive rock is formed deep within the Earth's crust. This type of rock is formed when magma cools and solidifies slowly beneath the surface. As the magma cools slowly, it allows for the formation of large mineral crystals within the rock. This is in contrast to extrusive rocks, which are formed when magma cools quickly on the Earth's surface, resulting in smaller mineral crystals or even a glassy texture. Therefore, the word "intrusive" accurately describes an igneous rock that is formed deep within the Earth's crust.Rate this question:
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- 8.
Which rock type is formed by high pressures and temperatures?
- A.
Igneous
- B.
Metamorphic
- C.
Sedimentary
- D.
All three
Correct Answer
B. MetamorphicExplanation
Metamorphic rock is formed by high pressures and temperatures. This process causes the original rock to undergo physical and chemical changes, resulting in a new rock with different mineral composition and texture. Igneous rocks are formed from the solidification of molten material, while sedimentary rocks are formed through the accumulation and compaction of sediments. Therefore, the correct answer is metamorphic, as it specifically describes the rock type formed by high pressures and temperatures.Rate this question:
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- 9.
The timescale of the rock cycle is:
- A.
Months
- B.
Decades
- C.
Millenia (a millenium is one thousand years)
- D.
Millions of years
Correct Answer
D. Millions of yearsExplanation
The rock cycle is a geological process that involves the formation, transformation, and recycling of rocks over time. This process includes different stages such as weathering, erosion, deposition, and lithification. These processes take a significant amount of time to occur, as rocks undergo slow changes over millions of years. Therefore, the correct answer is "millions of years."Rate this question:
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- 10.
Which of the following is NOT a type of weathering?
- A.
Saltation
- B.
Solution
- C.
Freeze-thaw
- D.
Exfoliation
Correct Answer
A. SaltationExplanation
Saltation is not a type of weathering. Weathering refers to the breakdown of rocks and minerals on the Earth's surface, while saltation refers to the process of particles being transported by wind or water in a bouncing or hopping motion. Weathering processes include solution, freeze-thaw, and exfoliation, which involve chemical reactions, physical forces, and expansion/contraction cycles. Saltation, on the other hand, is a transportation process rather than a weathering process.Rate this question:
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Mar 21, 2023Quiz Edited by
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