Rocks vary in color, size, texture and shape. They are classified based on how they were formed. Which of the following deals with the study of rocks? A. Biology B. Geology C. Paleontology D. Petrology 2. Halite is made when a body of seawater becomes closed off and evaporates and salt precipitates out and is deposited as crystallized halite. What type of sedimentary rock is formed? A. Clastic B. Chemical C. Organic D. Pyroclastic 3. Igneous rock is divided into two groups, extrusive and intrusive. Extrusive igneous rocks form when magma makes its way to its surface as lava and cools forming rocks. Which will be the characteristics of the crystals? A. Crystals are coarse grained. B. Crystals are fine grained. C. Crystals are very large. D. Crystals are phaneritic 4. Regional metamorphism occurs due to changes in pressure and temperature over a large region of the crust. It may happen when rock is buried deep below the surface or where pieces of the Earth’s crust collide. Which is a metamorphic rock? A. Breccia B. Conglomerate C. Marble D. Sandstone 5. Igneous and metamorphic rock can be buried and undergo tremendous heating and stress. What is the process of transformation of one rock type into another? A. Compaction B. Lithification C. Metamorphism D. Weathering 6. What type of rocks are formed from sediments over a long period of time? A. Igneous Rocks B. Sedimentary Rocks 7. This refers to the type of rock that was heated and compressed over time. A. Igneous B. Sedimentary C. Metamorphic D. All are correct 8. What is the natural process that causes one kind of rock to change into another kind? A. Weathering
The Correct Answer and Explanation is
Sure! Here are the correct answers with detailed explanations for each question:
1. Rocks vary in color, size, texture and shape. They are classified based on how they were formed. Which of the following deals with the study of rocks?
Answer: D. Petrology
Explanation:
Petrology is the branch of geology that specifically studies rocks—their origin, composition, structure, and how they are classified. While geology is the broader science that studies the Earth, including its materials and processes, petrology focuses strictly on rocks. Biology studies living organisms, paleontology studies fossils and ancient life, and geology is the overall science of Earth including rocks, minerals, and landscapes, but petrology is the specialized subfield focused on rocks themselves.
2. Halite is made when a body of seawater becomes closed off and evaporates and salt precipitates out and is deposited as crystallized halite. What type of sedimentary rock is formed?
Answer: B. Chemical
Explanation:
Chemical sedimentary rocks form when minerals precipitate directly from solution, typically water. In the case of halite (rock salt), it forms when seawater evaporates, causing the salt to precipitate and crystallize. Clastic sedimentary rocks, on the other hand, are formed from fragments of other rocks, organic rocks come from accumulated plant or animal debris, and pyroclastic refers to volcanic fragments, not sedimentary rocks.
3. Igneous rock is divided into two groups, extrusive and intrusive. Extrusive igneous rocks form when magma makes its way to its surface as lava and cools forming rocks. Which will be the characteristics of the crystals?
Answer: B. Crystals are fine grained.
Explanation:
Extrusive igneous rocks cool quickly on the Earth’s surface, allowing little time for large crystals to form. This rapid cooling results in fine-grained crystals that may be microscopic or very small, such as in basalt or rhyolite. In contrast, intrusive igneous rocks cool slowly underground, allowing large, coarse-grained crystals to form, called phaneritic texture.
4. Regional metamorphism occurs due to changes in pressure and temperature over a large region of the crust. It may happen when rock is buried deep below the surface or where pieces of the Earth’s crust collide. Which is a metamorphic rock?
Answer: C. Marble
Explanation:
Marble is a metamorphic rock formed by the recrystallization of limestone under heat and pressure. Breccia and conglomerate are clastic sedimentary rocks composed of broken fragments, and sandstone is also a sedimentary rock made from sand-sized particles. Marble’s origin as a metamorphic rock makes it the correct answer.
5. Igneous and metamorphic rock can be buried and undergo tremendous heating and stress. What is the process of transformation of one rock type into another?
Answer: C. Metamorphism
Explanation:
Metamorphism is the process by which existing rocks are transformed into metamorphic rocks due to heat, pressure, and chemically active fluids without the rock melting. Compaction and lithification refer to sedimentary rock formation processes, and weathering is the breakdown of rocks on the Earth’s surface.
6. What type of rocks are formed from sediments over a long period of time?
Answer: B. Sedimentary Rocks
Explanation:
Sedimentary rocks form from the accumulation, compaction, and cementation of sediments such as sand, silt, clay, or organic material over long periods. Examples include sandstone, shale, and limestone.
7. This refers to the type of rock that was heated and compressed over time.
Answer: C. Metamorphic
Explanation:
Metamorphic rocks are those that have been changed from an existing rock type by heat, pressure, or chemically active fluids. This process alters the mineral composition and structure without melting the rock.
8. What is the natural process that causes one kind of rock to change into another kind?
Answer: Metamorphism
Explanation:
Metamorphism is the natural geological process where existing rocks undergo physical and chemical changes due to heat, pressure, or fluids, transforming into new rock types without melting. This explains the dynamic rock cycle where igneous, sedimentary, and metamorphic rocks continuously change into one another
The study of rocks and their formation is fundamental to understanding Earth’s geology. Petrology, a branch of geology, focuses specifically on rocks — their types, origins, and classification. Rocks are broadly categorized into three main types based on how they form: igneous, sedimentary, and metamorphic.
Igneous rocks form from the cooling and solidification of molten material called magma. When magma cools slowly beneath Earth’s surface, it forms intrusive igneous rocks with large, coarse crystals. Conversely, extrusive igneous rocks form from lava that cools rapidly on the surface, resulting in fine-grained crystals due to the quick cooling rate.
Sedimentary rocks originate from sediments deposited over time, often in bodies of water. These rocks are classified further into clastic (formed from fragments of other rocks), chemical (formed from precipitation of minerals from solution, such as halite), and organic (formed from accumulated biological material). For instance, halite forms chemically when seawater evaporates, leaving behind crystallized salt deposits.
Metamorphic rocks arise when existing rocks are transformed by heat, pressure, or chemically active fluids without melting. This process, called metamorphism, can happen deep underground or at tectonic collision zones, causing mineral realignment and recrystallization. Marble, for example, is metamorphosed limestone, recognized by its recrystallized calcite grains.
The rock cycle describes how rocks continuously change through various processes: igneous rock can become sedimentary by weathering and lithification; sedimentary rock can transform into metamorphic rock under pressure and heat; and metamorphic rock can melt into magma, restarting the cycle.
Understanding these processes is critical for fields like geology, environmental science, and resource management, as rocks reveal Earth’s history and contain valuable resources.
