How Rocks are Formed | The Rock Cycle Explained !!
Summary
Rocks, which are on average around 100 million years old, undergo constant change on Earth. They are classified based on mineral quantity, chemical composition, and formation process. The rock cycle involves three main classes: igneous, formed from magma or lava; sedimentary, resulting from compression and cementation of small rock pieces; and metamorphic, arising from the transformation of older rocks due to heat and pressure. Igneous rocks can be intrusive, with slow cooling and large crystals, or extrusive, with quick cooling and small crystals. Sedimentary rocks often contain layers of sediment deposited over time in lakes and oceans.
Formation and Classification of Rocks
Rocks are constantly changing on Earth, with most rocks being around 100 million years old. They are formed in different ways and classified based on mineral quantity, chemical composition, and formation process.
The Rock Cycle
Earth acts as a giant recycling machine where rocks are redistributed and transformed from one type to another. The rock cycle involves three main classes of rocks: igneous, sedimentary, and metamorphic.
Types of Igneous Rocks
Igneous rocks are formed from magma or lava. They can be intrusive, with slow cooling allowing large crystals to form, or extrusive, forming from lava cooling quickly and containing small crystals like basalt and granite.
Formation of Sedimentary Rocks
Sedimentary rocks are formed from the compression and cementation of small rock pieces transported by weathering processes. They often contain layers of sediment deposited over time in lakes and oceans, including minerals and organic matter.
Types and Transformation of Metamorphic Rocks
Metamorphic rocks are formed from the physical or chemical transformation of older rocks due to heat and pressure. They can be formed from other metamorphic, sedimentary, or igneous rocks, like nicest from granite or metabasalt from basalt.
FAQ
Q: How are rocks classified?
A: Rocks are classified based on mineral quantity, chemical composition, and formation process.
Q: What are the three main classes of rocks in the rock cycle?
A: The three main classes of rocks in the rock cycle are igneous, sedimentary, and metamorphic.
Q: How are igneous rocks formed?
A: Igneous rocks are formed from magma or lava.
Q: What are the two types of igneous rocks based on cooling rate?
A: The two types of igneous rocks based on cooling rate are intrusive and extrusive.
Q: How are sedimentary rocks formed?
A: Sedimentary rocks are formed from the compression and cementation of small rock pieces transported by weathering processes.
Q: What do sedimentary rocks often contain?
A: Sedimentary rocks often contain layers of sediment deposited over time in lakes and oceans, including minerals and organic matter.
Q: How are metamorphic rocks formed?
A: Metamorphic rocks are formed from the physical or chemical transformation of older rocks due to heat and pressure.
Q: From what types of rocks can metamorphic rocks be formed?
A: Metamorphic rocks can be formed from other metamorphic, sedimentary, or igneous rocks.
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