Minerals and Rocks
Which rock type appeared first on Earth? Why?
Igneous rocks came first, because sedimentary and metamorphic rocks are formed from preexisting rocks.
How do igneous rocks form?
Igneous rocks form from magma.
What type of igneous rock contains large mineral crystals? Explain why.
Intrusive igneous rock contains large mineral crystals. The large crystals in intrusive igneous rocks form when magma cools very slowly. Magma that is trapped beneath Earth's surface is insulated by surrounding rocks, and cools and hardens over very long periods.
What is the difference between extrusive and intrusive igneous rocks?
Intrusive igneous rocks are cooled down slowly beneath Earth's surface, and large crystals form. Extrusive igneous rocks cool down rapidly on Earth's surface, and crystals do not form at all or are very small.
How are metamorphic rocks formed?
Metamorphic rocks are formed by rocks that are changed by heat and pressure.
What rock type does the principle of superposition apply to and how is the principle of superposition used to study the history of life on Earth?
The principle of superposition applies to sedimentary rock. It is used to study the sequence of life on Earth. Sedimentary rocks are the only rocks that contain fossils and therefore, a record of ancient life. By applying the principle of superposition, scientists know that fossils in the upper layers are the remains of animals that lived more recently than the animals that were fossilized in lower layers.
What is the principle of superposition?
The principle of superposition states that in undisturbed rock layers, the oldest layer of rock will be on the bottom, while the youngest layer will be on the top.
In an earthquake-prone area, which earth material - igneous rock or sedimentary rock - would be better for constructing buildings? Explain your answer.
The rock with the most solid structure will be the best choice for construction in an earthquake-prone area. Because sedimentary rock is formed as the result of compaction and cementation of preexisting rock particles, sedimentary rock isn't as rigid and doesn't have the same strength as igneous rock. As magma cools and solidifies, the minerals crystallize, forming igneous rock. Igneous rock forms a stronger, more stable base on which to build. The mineral cement that holds rock particles together in sedimentary rock can be shaken loose and broken in an earthquake.
Radioactive isotopes are used to determine the ____________ (absolute/relative) age of rocks.
absolute
Sedimentary rocks are the only rocks that can potentially contain ____________ (fossils/minerals).
fossils
