Rocks formed due to alteration of original structure due to heat and excessive pressure are called
🪨 Understanding Rock Formation Processes
The key to answering this question lies in the definition of the three main rock types, which are classified based on how they are formed.
🔬 Detailed Analysis of the Options
C. Metamorphic Rocks
This is the correct answer. The word "metamorphic" comes from the Greek words 'meta' (meaning change) and 'morphe' (meaning form). Metamorphic rocks are literally "changed form" rocks. They are created when a pre-existing rock (called the parent rock or protolith) is subjected to intense heat and excessive pressure deep within the Earth. This process alters the original rock's mineral composition, texture, and structure without melting it.
A. Sedimentary Rocks
This is incorrect. Sedimentary rocks are formed by the deposition, compaction, and cementation of sediments on the Earth's surface. The process involves settling and hardening, not alteration by heat and pressure.
B. Igneous Rocks
This is incorrect. Igneous rocks are formed from the cooling and solidification of molten rock (magma or lava). The process is about a change in temperature from liquid to solid, not the alteration of an existing solid rock.
D. None of these
This is incorrect as the definition perfectly describes metamorphic rocks.
➡️ Common Examples of Metamorphism
Understanding how common rocks transform is key to remembering this concept.
| Parent Rock (Original) | Rock Type | Becomes... | Metamorphic Rock |
|---|---|---|---|
| Limestone | Sedimentary | ➡️ | Marble |
| Sandstone | Sedimentary | ➡️ | Quartzite |
| Shale | Sedimentary | ➡️ | Slate |
| Granite | Igneous | ➡️ | Gneiss |
💡 Study Tips
- "Morph" means "Change": This is the most important clue. If you see the word "alteration" or "change" in a question about rock formation, the answer is almost always metamorphic.
- Heat + Pressure = Metamorphism: This is the fundamental equation for this rock type. Think of it like baking a cake - you take ingredients (the parent rock) and use heat and pressure to turn them into something new.
- Know the Keywords:
- Igneous = Molten, Cooling, Magma, Lava
- Sedimentary = Deposition, Layers, Sediments, Fossils
- Metamorphic = Heat, Pressure, Alteration, Change