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How are Rocks Formed? Igneous, Metamorphic, and Sedimentary Rocks

How are Rocks Formed? Igneous, Metamorphic, and Sedimentary Rocks

Ever wonder why are there several types of rocks and where do they come from? Did you know that rocks have many lives? Not obviously, but rocks can die and live again and again. As in rocks can be deformed and can be formed again.

how rocks are formed_ igneous, sedimentary, metamorphic

Rocks can be differentiated based upon their characteristics and how they are formed. And these processes involved in how rocks formed are melting & cooling, weather & erosion, and heat & pressure.

How are rocks formed?

  • Melting and cooling– rocks in the earth surfaces that are subducted through the earth’s inner layer are melted to form lava. When the lava reaches the ground from a volcanic vent. For example, it is now called magma. The magma will be cool down. Therefore, the magma will be solidified to form a rock. It is considered as an Igneous rock just like granite, basalt, and obsidian.
  • Weathering and erosion– In this process, the rocks will be broken down into sediment and will undergo compacting and cementation that will produce sedimentary rock like sandstone, shale, and limestone.
  • Heat and pressure– rocks from deep under the ground become soft and will be squeezed. It will be foliated to form metamorphic rocks like slate, phyllite, and gneiss.

Rocks go underneath the earth’s surface and will rise again through some processes. It is also called the rock cycle.

How are igneous rocks formed?

How are igneous rock formed

Igneous rocks are formed under the following conditions when magma cools down.

Types of Igneous Rocks:

  • Intrusive – Takes thousands of years to cools down
  • Extrusive – Fast cooling time
  • Plutonic – Takes millions of years to cool down

Igneous rock can change into a sedimentary rock if that rock undergoes weathering and erosion as well as a metamorphic rock if heat and pressure are applied to it.

Examples of Igneous Rocks:

  • Granite
  • Obsidian
  • Scoria
  • Pumice


How is granite formed?

Granite is formed when magma cools down.


How are sedimentary rocks formed?


Sedimentary rocks can be formed into igneous rocks if it is melted underneath the earth’s surface and cooled on the ground. It can also turn into a metamorphic rock if heat and pressure take place.

To keep it simple, the sedimentary rocks are formed under the following circumstances:

  • When igneous or metamorphic rocks undergo weathering and erosion
  • When sediments are compacted and cemented.


Examples of Sedimentary Rocks:

  • Sandstone
  • Limestone
  • Shale
  • Conglomerate
  • Gypsum


How are metamorphic rocks formed?


Metamorphic rocks are formed when igneous and sedimentary rocks are subjected to heat and pressure.

Examples of Metamorphic Rocks:

  • Slate
  • Gneiss
  • Quartzite
  • Marble


How is magma formed?

Magma is formed when igneous and metamorphic rocks are melted.

You can’t really notice these rocks change because it will take more than a human life span before it undergoes some different processes.