1. Which kind of rock is typically formed by the cooling and solidification of lava or magma?
Answer: A
Igneous rocks are typically formed by the cooling and solidification of lava or magma.
Igneous rocks are formed through the cooling and solidification of molten rock, either from lava that erupts onto the surface or from magma that cools underground. This process is fundamental to the formation of various types of igneous rocks, which are characterized by their crystalline structure.
A) Igneous
This option is correct because igneous rocks are explicitly defined as those formed from the cooling and solidification of lava or magma. This category includes both intrusive igneous rocks, which crystallize beneath the earth's surface, and extrusive igneous rocks, which solidify on the surface after volcanic eruptions.
B) Metamorphic
Metamorphic rocks are not formed from the cooling and solidification of lava or magma. Instead, they originate from existing rocks that undergo transformation due to high pressure, high temperature, or chemically active fluids. This process alters the mineral composition and structure of the original rock.
C) Clastic sedimentary
Clastic sedimentary rocks are formed from the accumulation and lithification of sediment particles derived from the weathering and erosion of pre-existing rocks. This process is distinct from the formation of igneous rocks, which involves molten material rather than solid fragments.
D) Chemical sedimentary
Chemical sedimentary rocks are formed by the precipitation of minerals from solution, often due to evaporation or biological activity. This type of rock formation is unrelated to the cooling of lava or magma, which is the defining process for igneous rocks.
Conclusion
Igneous rocks are the only type of rock listed that is directly formed from lava or magma, making option A the correct choice. The other options—metamorphic, clastic sedimentary, and chemical sedimentary—are formed through entirely different geological processes that do not involve the cooling and solidification of molten material. Thus, option A is definitively the correct answer.